Posts Tagged ‘moly grease’
by Tom Gaylord, a.k.a. B.B. Pelletier
My rifle is actually a BSA Super Meteor.
The last report on this BSA Super Meteor was on October 15. That’s how long it’s been since we saw this gun in print. But in the background, I’ve been doing lots of things that I’ll share with you today.
The last time we looked at this rifle, I was taking it apart and getting a lesson on how it was built and what was wrong with it. To summarize for you, this BSA Meteor is made from folded metal, in the same way Daisy BB guns are made. And the piston head was attached to the piston by means of an E-type circlip that was incapable of standing up to the stress. I can tell that by the damage that was done when that clip let go — but more because the Brits have invented a much better solution for fixing this gun today, when it does break down — and all of them are going to break!
I sent my order to T.R. Robb in the UK for a replacement piston head, o-rings and spacers. The problem is that when I sent in that order I didn’t pay attention to the fact that the same order button also got a piston head for a BSA Scorpion pistol, which is larger than the Meteor head. Well, guess which one Mr. Lysdexic ordered?
That’s right, I ordered the Scorpion piston head. And a couple days later, when I realized what I’d done and contacted T.R. Robb, they had already shipped the order. But to their credit, they sent a second piston head — this one was for a Scorpion, too. That’s right! They sent me 2 Scorpion piston heads and no Meteor head! But I’ll give them credit for trying to help me, for being very generous and refusing my offer to pay for the second head, and for being very prompt in shipping both heads. I had them in less than 10 days.
So, blog reader David Enoch — I now have a spare BSA Scorpion piston head that I believe you said you needed. The price will be right, too. You’ll pay what I paid, which was nothing.
Lots to see here. The replacement piston head is the shiny one on the left, the darker original is on the right. Obviously, the replacement part is larger and has to be cut down to fit. The blue spacer and 2 o-rings are just some of the soft parts that came in the kit. There were a total of 4 o-rings of different sizes and 2 more spacers of varying thicknesses. They allow you to set the power of your airgun, and they also allow for differences in the tolerances of different guns.
When I saw how large the piston head was, I knew it wouldn’t fit. I asked my friend Otho to cut it down for me on his lathe. He also had to cut the o-ring channel deeper at the same time.
Silly me — I thought that would solve everything. So, Otho took the head and had it back to me in a week. Then, I assembled it to the end of the piston and tried to insert the piston back into the spring tube. But it wouldn’t fit! I’d taken it out several weeks earlier, and now it wouldn’t fit back inside! It was like that pair of blue jeans that used to fit, before they suddenly and quite mysteriously shrank. I hate it when that happens — especially to jeans I’ve worn for years!
I took a more critical look at both the spring tube and the piston. Glory be — they’re both made of folded metal like a Red Ryder! Except that Red Ryder spring tubes are generally round, while both of these pieces had variable shapes, with a tendency toward the oval.
The tail end of the piston. Here you clearly see that it’s folded metal, tack-welded at each end.
At least that’s the theory! Here you see the weld at the piston head end has broken. Wonder why the piston is no longer round?
And, on the other side of the piston, opposite the broken weld, the solid metal has also cracked! Here you can see the nut that now holds the piston head to the piston body. It’s not about to break off like the circlip did!
Looking at just the condition of the piston gives you an idea of the shape this rifle is in. I don’t think the design of the rifle caused all this damage. I think people continued to try to cock and fire it after the piston head separated from the piston, and they hammered it into the mess you see here.
I examined the interior of the spring tube very critically at this point and found a lot of metal galling (shiny areas that indicate the scraping of metal against metal without lubrication). There was also a fair bit of surface rust. I also found that some of the folded metal edges of the spring tube that hold the trigger parts were bent into the interior of the spring tube and were blocking the passage of the piston. I fixed those with a Dremel tool, but the inside of the tube was too deep to reach.
I showed the spring tube and piston to Otho, who agreed with me as to the extent of the damage. He felt he might be able to clean out the tube with a tool that holds strips of abrasive paper and is spun in an electric drill. I don’t own that tool, so I was only too happy to let him have a go at it. He also said he could tack-weld and refinish the piston where it was separating.
So, Otho came to the rescue once more. And he was true to his word, because a week later I got back the tube and piston, ready for assembly. But that wasn’t the end of the rifle’s problems!
Otho welded the broken piston and dressed it round again.
Otho also welded the back side of the piston where it was cracked.
Loose barrel pivot
I had discovered that the barrel wobbled from side to side when I first got the rifle. And a little research online told me this is a common problem with Meteors from the 1970s. Apparently, when the forearm stock screws are tightened, the shape of the stock allows them to pull apart the action forks that hold the barrel breech. It’s a design flaw of the rifle, and the solution is to not over-tighten those screws. But how to fix it — since the barrel pivot is a pin, rather than a bolt? Well, this is something I know how to do.
I chucked the forks in the padded jaws of my bench vice and closed the jaws on the forks. When there was some inward tension on them, I hit the outside vice jaw with a 2-lb. ball-peen hammer, which sent a shock wave into the metal of the action forks and realigned their crystalline structure. Or at least that looks cool when I write it. I haven’t got a clue what really happens! All I know for sure is that when you do this, the metal takes a set in the new position, and now the action forks are about 5 thousandths of an inch smaller then the breechblock of the barrel that has to fit between them.
Finally, all the faults had been corrected, as far as I knew. The piston now slides into the spring tube with only a little friction, not unlike a Weihrauch piston in a Weihrauch gun. It was time to assemble the rifle!
Otho and I both think whoever designed this Super Meteor Mark IV was a genius at eliminating cost and making one thing do many jobs. The way this air rifle is designed should be a study in an engineering course, but the students would first have to know how others had done the same things with other spring-piston powerplants. At every turn, you can see the embodiment of the Spartan design.
And the parts that need to be hard are hard! I mean glass-hard! There’s no wear on any of the trigger parts, or on the piston, where it’s held by the sear. The boys at BSA knew what they were doing.
Since there had been so much metal galling in the spring tube, I first lubricated it with Moly Paste before any parts went back in. The molybdenum disulphide particles will bond with the metal surfaces and will not wash out over time. I applied this paste (which is a thick grease) with a swab made from a long thin dowel rod covered with a paper towel on one end.
This simple swab can be used to clean the inside of spring tubes/compression chambers, as well as to lubricate them.
After the inside of the spring/compression tube was lubricated, I also lubricated the outside of the piston head and piston tail with the same moly paste. I’d like to say a word about the piston head now. The kit of parts I was sent had 3 spacers of differing thicknesses. Any of them will work, but each gives you a piston head of a different length when it ‘s fastened to the piston body.
The way the Meteor is designed, adjusting the length of the piston head controls the power of the rifle. A shorter piston head will give a longer piston stroke and therefore greater power. I don’t want power. I want a smooth rifle that’s easy to cock and is also easy to shoot. So I went with a thicker spacer on the head.
Now, I lubricated both the piston head and the tail with moly. The center of the piston body can be left dry because it’s narrower than the ends and will never touch the inside of the spring tube.
The piston head is lubed with moly paste. No precision is required for this application because this stuff spreads as the gun is cocked and fired. The other end of the piston got the same treatment before it was slid back into the spring tube.
Once the piston was in the tube, I coated the mainspring with Beeman Spring Gel and slid it into place inside the piston. Don’t look for that product anywhere — it’s obsolete. It was a viscous silicone (Beeman only says it’s a synthetic in their catalog; but given where it’s going, I’m pretty sure it’s silicone) grease that dampened vibration without slowing the gun much, if any. So, pretty much any viscous silicone with the consistency of toothpaste should suffice. Or, you could do it the old-school way and just use a lithium-based grease.
The powerplant went together the same way it came apart; but the barrel, which was the next item, was harder to install because the action forks were now smaller, thanks to my repair. Nevertheless, the barrel did go into the action forks of the spring tube (I “buttoned” it in using the baseblock to spread the forks slightly), with the cocking link locked inside the piston and lots of moly grease on all metal surfaces that touch.
When it came time to close the barrel, I got a small surprise. It seems the spring-loaded chisel detent (the chisel-looking thingie that holds the barrel shut when the gun fires) was sticking out so far that the barrel wouldn’t close! Examination revealed that the detent is held in the baseblock by the pivot pin that passes through. How in the heck was I going to do that?
Well, if you think like a redneck cheapskate, which I am trained to do, you insert the pivot pin partway, lever the chisel detent back as far as it will go and then tap the pivot pin home. I could have closed my eyes for this maneuver, it went so smoothly. Obviously, I’d discovered something that the original 28-year-old BSA assembler, Trevor, could do 175 times in an 8-hour shift back in 1978.
From there, the only big task was to get the mainspring back inside the spring tube all the way. It only stuck out the end of the tube less than an inch, but it also had to go another full inch into the tube, where it would be held by a crosspin that’s profiled on one side to capture the base of the spring guide. It’s easier to just show you.
This is the side of the assembly pin that fits inside the base of the mainspring guide and holds it inside the rifle.
This 58-cent tool was made from a 4-inch plastic sprinkler pipe in about 20 minutes. With the action in the mainspring compressor, it pushes the washer at the base of the mainspring, while allowing the crosspin to be inserted through its slot. It isn’t beautiful, but it worked both times I used it and looks like it will hold up for dozens more jobs like this.
And the pin is back in place. The contours on the other side of the pin have meshed with the base of the spring guide.
I showed you these parts and the trigger parts in the earlier reports, namely in Parts 2 and 3. So I’m covering ground that I’ve already explained. When I took the rifle apart back in October, I didn’t have to use a mainspring compressor; but to get the mainspring back in place and insert the crosspin, I did. And it was easy.
And the remainder of the airgun went together exactly as it should. I have a theory. Whenever something goes together easily, it means I’ve left out something. I’m in my wetsuit but have forgotten to put on my briefs! I remember learning how to disassemble and assemble the M1 Garand rifle. I thought I could never learn, but a few weeks later I was stripping it like a pro. That’s the way BSA spring rifles are, I guess. You’d like them to come apart in 30 seconds without hand tools, but they don’t. However, once you’ve been down the path a few times, I’m sure the job seems simple.
This is the part I dreaded. Sure the parts were back together, but who was to say they were where they should be? Only cocking and firing the gun would tell me that. So I did. And it did! Hurrah!
The only task left to do is to clean the barrel. I had close to 2 months to do that while it was off the rifle; but to tell the truth, I wasn’t sure if I would be able to get the gun back to functioning again. No sense doing a great job on a barrel I’ll never use. But now the gun is working, so the next report can be about the velocity.
by Tom Gaylord, a.k.a. B.B. Pelletier
El Gamo 68 is a futuristic breakbarrel from the past.
I last reported on this rifle on August 8 of last year. And that was Part 5! I had just tuned the rifle with a new mainspring and proper lubricants and was wondering what the changes would be. I was ready to report on it several months ago when I discovered that it wouldn’t cock. After fiddling with the trigger adjustments awhile with no success, I set it aside and moved on — thinking that the gun would need to be disassembled.
I disassembled it last week and discovered there was nothing wrong! The sear was working properly, or at least it seemed to be when I played with it as the gun was disassembled. I relubricated everything and put it all back together and was going to write Monday’s report on it. But the trigger still didn’t work! ARRGH!
This time, I remembered that when I got the gun the trigger was also a bit iffy, so I fiddled with the adjustments WAY outside the normal realm and, presto! I got it working again. Oh, it took a couple hours and there were some accidental discharges when the barrel was closed (direct sear!), but I solved all that by giving the sear way more contact than it needs.
Now the trigger releases at about 12 lbs., but at least it’s safe. Today, I’ll share with you how the tuned gun does at 25 yards — heavy trigger and all.
One other thing I did to the rifle was lubricate the leather piston seal with 10 drops of 3-in-One oil, leaving the rifle standing on its butt for two days afterward. The oil was allowed to slowly soak into the leather, which it did, but to protect the carpet and walls (Edith–Are you listening?) I put a long drop cloth in front of the rifle when I shot it.
Today’s test is a deviation from my normal pattern. I’ve tuned this gun and not yet reported the new velocities, and yet here I am shooting for accuracy. I decided to do it that way; and if I got good results, I would test the velocity next. I’m not changing the usual way of doing things — this is just an exception.
The first pellet I tested was the RWS Hobby. I chose it for its light weight and because it’s often accurate in lower-powered spring rifles and pistols. Sitting 25 yards from the target, I have to admit that I was wondering if the rifle had enough power to hit that target — let alone shoot a decent group.
Five of the first 10 pellets were detonations from the oiled piston seal. And the smell of burning oil was in the air. The Hobbys landed in a vertical group that was pleasingly tight from side to side. I was prepared to blame the verticality on the dieseling, but the truth is, that wasn’t the problem. The gun just doesn’t want to shoot Hobbys at 25 yards. That’s not too surprising since 25 yards is about the maximum distance for any wadcutter pellets, in my experience.
Air Arms Falcon
The second pellet I tested was the Air Arms Falcon, a 7.3-grain dome that’s often accurate in spring rifles. I used the spotting scope only on the first shot, which was a detonation, to make sure it was on the paper. There were 4 detonations in the 10 shots. I didn’t look at the target again until I walked down to change it. Boy, was I surprised by what I saw! To paraphrase Crocodile Dundee, “Now, THAT’S a group!” For open sights at 25 yards and 65-year-old-eyes, it ain’t too bad!
Remember, I’m shooting 10 shots — not 5. So this kind of group really proves the rifle can shoot. It also proves this old man can still hit things when the rifle does its part! So much for the problems of the droopers and gas springs! I needed this validation after some of the disappointing tests I’ve done recently.
The heavy trigger apparently is not causing much of a problem for me. I think that’s because the rifle is rested. If I were shooting offhand, I’d want a lighter trigger-pull.
JSB Exact RS
Next, I tried JSB Exact RS pellets. This is another 7.3-grain dome from JSB (JSB also makes Air Arms Pellets) and is very often accurate in many different airguns. And this is one of them. The group is slightly larger than the Falcon group, but the two are so similar that I would call it a tie.
The last pellet I tried was the RWS Superdome, which often does well in lower-powered spring rifles. This time, however, it didn’t. Ten pellets produced a 1.765-inch group. It didn’t disappoint me, though, because the Falcon and JSB RS groups looked that much better. It showed that the earlier Hobby group wasn’t just a fluke of bad luck — the gun simply likes what it likes.
This test was calming for me. It was slower than many of the tests I’ve run in the past month, and the results were more based on me as a shooter rather than on the equipment. I find that I like that a lot!
The El Gamo 68 XP is operating well right now, except for the heavy trigger that I’ll probably keep just as it is for a while. The tuned powerplant is now smoother with less of a jolt. I noticed in this test that each pellet has a firing characteristic of its own. The two JSB pellets were definitely the smoothest of the four tested, and the Hobbys were the roughest.
This is such an odd airgun, with the fat heavy butt and no forearm to hold. Yet, it shoots like a thoroughbred. With the new tune, it cocks smoothly and just feels good to shoot — I don’t have any better way of describing it. I wish you could all try one, but since you can’t, I will, again, recommend the Air Venturi Bronco, which is the closest thing still being made today.
by B.B. Pelletier
Tune is slang for tuneup, and in airguns a tuneup can range from a quick lubrication all the way to a major overhaul of the powerplant and trigger. Everything in between these two extremes is also fair game. So, lesson one is that a tune can be anything that changes and hopefully improves the airgun’s performance.
I’m going to address a breakbarrel spring gun in today’s report. Other powerplants can also be tuned; but the steps are different, and the results will differ from what you get with a spring gun tune. Since the majority of airgun tunes are performed on springers, it’s appropriate to look at them first. And the breakbarrel is the No. 1 type of spring gun.
Victor asked what was meant by a tune, but I suspect that others would like to know what’s involved, as well, so today we’ll look at airgun tuning in all its complexity. Let’s begin with a brand-new spring gun and see why we would tune it and what might be done.
Smoothing the edges
Most new spring guns have sharp edges on all the mating powerplant parts. Sometimes, these edges interfere with the movement of the parts. These edges are worn down during a long break-in period, which is why a gun gains velocity as it wears in. But you can also remove these edges and burrs with small files, and that is one thing that a tuneup can do.
Key places to look are the cocking slot, the piston slot, the cocking linkage and, if there’s an interface between the linkage and the piston, that’s a prime place to look for burrs and sharp edges. The forward edge of the cocking slot is especially important, because it can slice a new piston seal when it’s installed…and that will ruin the seal. The end cap and sides of the trigger mechanism should also be checked.
The action forks that the pivot bolt passes through is another place to look for burrs and sharp edges, as well as the sides of the baseblock that the barrel is pressed into.
There are also burrs and sharp edges that don’t affect the operation of the powerplant. These do not go away with use and they can be left alone if you like. However, if you plan to take the powerplant apart in the future, these edges and burrs will be waiting to cut you.
Probably the most common thing done during a tune is lubrication. New guns can have either too much grease or not enough. And most of them have the wrong kind of grease. The factories use a general machine grease, but there are much better greases that can be used.
For metal-to-metal contact, nothing is better than grease that contains a high concentration of molybdenum disulfide. Moly isn’t a grease — it’s a solid particle that’s ground very fine and mixed with grease for application. When it comes in contact with metal under some pressure, the particles bond with the metal on the surface, forming a layer of extreme low friction. That layer is durable and allows other metal to slide across the surface it’s on.
We don’t appreciate how low-friction moly is, because the grease it’s in raises the coefficient of friction. But custom tuners are known to burnish certain parts of a gun — like the inside of the compression tube — with dry moly particles. This process takes a long time, as the moly doesn’t want to cooperate; but once it’s, done you have a surface with very low friction. Jim Maccari and I split a pound of moly powder, and my half was in several large bottles. It’s a lifetime supply for a full-time tuner!
Another place where moly powder comes into play is on the mating trigger sear surfaces. I’ll have more to say about this in a moment, but this is a custom tuner’s trick. The action fork and baseblock can also benefit from a burnish of moly.
I don’t burnish anymore, though. Moly grease, such as Air Venturi Moly Paste, will do the same thing over time as it gets worked into the action through the process of shooting.
But not every springer needs moly grease. The older guns with leather piston seals actually do better with a white lithium grease. The grease serves as fuel for the constant dieseling of all spring-piston guns, and leather seals burn more fuel than synthetic seals do. For this same reason, I lube the mainsprings of the lower-powered springers like a Diana 27 with the same white lithium grease.
Does it bother you that I said all spring piston guns diesel? Well, they do. Don’t confuse dieseling, which is normal and even good, with detonation — which is when you here a low bang. That’s too large an explosion for your gun, and you don’t want to do very much of it.
The barrel pivot and the forks through which it passes is another place to grease. The right grease (moly) applied here reduces the cocking effort by 10 pounds!
The mainspring is the other place that gets lubed, and often it’s to stop the vibration, though I’m going to tell you in a moment a better way to do. For this, people use black tar, or what Jim Maccari calls Velocity Tar. It’s just a very viscous grease with a high adhesion that feels tacky to the touch. Farmers and heavy equipment operators know it as open gear lubricant. Most of the different greases like this will slow your gun to some extent, but there are products like Velocity Tar which, if used sparingly, seem to not phase the velocity at all.
Remove all the play
Okay, lubricating a gun to smooth the firing cycle is a redneck approach. Many people, including me, do it that way. But there’s a more elegant way if you’re willing to work. That way is to remove all the play in the various moving parts. The piston and mainspring are the primary parts involved.
The piston in a factory gun fits well inside the spring tube, but there’s a looseness to allow for manufacturing tolerances. The piston seal takes up a lot of the slack, but it’s located just at the front of the piston. The rear is free to move in all directions. While the space is small, this is where some of the vibration comes from.
To tighten the piston, it’s possible to put small bearings at the front and rear of the piston. These are usually small, round spots of synthetic material such as Teflon or nylon. Typically, three are placed at the front and three more at the rear. They are spaced evenly around the piston body, and the front ones are offset from those in the rear. If they fit the spring tube exactly, the piston rides on them, and then a moly coating really does its work.
The next critical fit is the mainspring, and here it’s sometimes possible to buy a spring that fits the spring guide in the rear and the piston rod in the front very tightly. Tuners call this close fit being “nailed on.” When you have a close fit like this, good moly lubrication is essential, or the close fit of steel on steel will cause galling, which is a form of burnishing that causes friction, vibration and excess heat.
If you can’t find a spring that fits this tight, you can always have a custom spring guide made that does fit the spring you have. Then, inside the piston, you can put a steel shim that fits between the mainspring and the inner walls of the piston. It’ll look shoddy; but once the powerplant is together, it’ll stay in place. And moly is essential here for the mainspring and the guide. This is called a “beer can” tune, because people often use cans to make the shim.
Another trick people use is to put shims behind the mainspring on the spring guide end. This puts the mainspring under more tension and gives more power. You have to make sure there’s enough room to cock the rifle when doing this, because it’s possible to shim the spring too much.
New airgunners assume that the stronger the mainspring, the more powerful the airgun. That isn’t always the case. Piston stroke has more to do with power than the spring rating. I always look for a weaker spring because I know it won’t subtract that much power from the gun. A coating of tar will do more to slow down a gun than a weak spring, as long as the spring fits well.
A final word on the mainspring is to notice that each end is usually a different size. Try to match the end with the spring guide or piston rod that fits best.
Piston seals used to be a real big reason for tuning a spring gun, because they wore out or melted from friction. Today’s seals are pretty well made, though there will always be some cheapies that come to market from time to time. The thing about the piston seal is to ensure that it fits the bore of the compression tube without adding too much additional friction. Some is unavoidable, but it’s easy to go overboard. The modern parachute piston seal that expands as it compresses air is very sophisticated, and shouldn’t be too difficult to size correctly. To reduce the diameter, put the seal on the piston and rotate the piston against sandpaper. Be careful to keep the sides of the seal parallel to the compression chamber bore while doing this. It usually only takes a minute or two for this job.
The trigger can be adjusted and lubricated during a tuneup. I lubricate with moly grease, because a trigger is not a part that works by friction. No matter how low you get the friction, the trigger should always be safe…but this is a place where home tuners often have problems. They either stone or file the mating sear surfaces and put a dangerous angle on them. Then, they lubricate them with moly. These are the triggers that slip when cocked.
People are also known to adjust a trigger to have too fine mating surfaces, and once more, they’ll slip when cocked. My advice is to lube first, then let the trigger work for several hundred shots before you adjust it. I would keep stones and files away from triggers unless you’re certain that you know what you’re doing.
This part is often overlooked and can sometimes give you a large boost in power. The breech seal doesn’t have to stand proud of the breech to work well. It all depends on how the gun is designed. But don’t overlook the possibility of improving performance by raising the breech seal a few hundredths of an inch.
I hope this report answers most of the questions you have regarding tuning an airgun. As I said at the start, a tune can be any of these things, or all of them. A professional tune is usually all, but you should discuss the specifics with your airgunsmith before letting him start the work.
by B.B. Pelletier
Fresh from the closet, another fine Crosman 160 emerges into daylight. We’ll watch this one blossom.
Today, I’ll report on the cleaning of Jose’s Crosman 160 and the adjustment of the trigger. This rifle was quite rusty when I got it, so today it came out of the stock for a thorough cleaning. The barreled action comes out of the stock by removing one nut on the bottom of the forearm and by removing the safety switch. To remove the switch, it must be turned toward SAFE while you push it out of the triggerguard. It will pop right out when you get it in the right position.
The broken safety has been pushed out, and the nut removed from the stock. That’s a new safety to the left of the broken one. The barreled action is now ready to come out of the stock.
Once the action was out of the stock, I could see that it was far rustier than I originally thought. The rust that could be seen when the rifle was intact was just surface rust, but the stock was hiding deep active rust that had to be removed.
This was under the stock — heavy, active rust that must be dealt with!
I used Ballistol and a special scrubbing pad I bought at a recent gun show. A friend of mine says this pad looks like a stainless steel pot scrubber. All I know is that it removes all the rust and doesn’t harm the blue.
I used Balistol in a spray bottle and a special metal scrubber to remove the rust.
I was surprised at how fast the rust was removed. In all, it probably took no longer than 15 minutes to completely clean all the metal parts.
With the gun finally clean, it was time to address the trigger. I mentioned in Part 1 that this trigger is one of the finest ever put on an inexpensive air rifle, and it can be adjusted to a very light, crisp pull. When I got the gun, the single-stage trigger had lots of creep and was breaking at 5 lbs., even. Something had to be done about that.
The Crosman 160 trigger is an adaptation of a 15th century crossbow trigger, where a rotating piece called a nut forms the sear that releases the hammer — in the case of the pellet rifle. The nut is a lever that’s shaped like a circle. It allows a small force (the sear) to overcome a greater force (the hammer spring) through leverage. No filing or stoning of the trigger contact surfaces is necessary, because the trigger doesn’t work like a conventional one.
From Sir Ralph Payne-Gallwey’s book, “The Crossbow,” (published in 1903) this illustration of a 15th century crossbow nut shows how a great force can be overcome by a smaller one.
But the Crosman 160 trigger is more sophisticated than the crossbow trigger. It allows the adjustment of the sear contact area and also the point at which the trigger stops. This gives the shooter a safe trigger that breaks cleanly, yet feels like an expensive precision target trigger.
The trigger in the subject rifle was about as filthy as I’ve ever seen. This trigger has a sideplate that allows the user to watch the adjustments of the parts and even to cock and fire the trigger with the parts exposed. Normally, this sideplate keeps the parts inside pretty clean, but you can see from the photo what I saw inside this one.
I’ve removed the trigger unit from the action here. It isn’t necessary to do this, and in fact you must be able to cock the rifle when you adjust the trigger, so leave it connected. I did this for cleaning purposes.
Compare this photo to the previous graphic, and you’ll see all the important trigger parts. This is before cleaning. The rusty red part at the upper right is the nut that’s the sear.
I removed the trigger blade from the trigger assembly and cleaned it outside the trigger box, but all other parts were cleaned where they were situated. Ballistol on cotton swabs worked wonders at removing the rust, dust and dirt. And it left all the parts with a lubricated surface.
The two trigger adjustment screws were stuck in place by dried grease, so Ballistol had to dissolve that before I could clean the threads. The final touch was to apply moly grease to the mating surfaces of the trigger blade and the rotating nut that serves as the sear. Then it was time to adjust the trigger.
The first step was to back off the trigger return spring, which is located at the bottom rear of the trigger box. With this spring relaxed, you can feel the engagement of the sear much better.
Next, I adjusted the top screw, which adjusts the trigger/sear contact area. I set it very quickly because I’ve adjusted dozens of these triggers over the years and I know what they need. You may have to adjust the screw then cock the rifle and fire it several times to get the engagement you want. The engagement needed is very narrow, and it looks like the trigger is about to slip off the sear; so I always give the cocked rifle a bump test after adjusting the trigger, just to be safe. If I can’t jar the trigger off the sear, it’s safe.
The final screw to adjust is the trigger stop or overtravel screw. It stops the trigger blade after the sear has released, and the closer this is to the release point without impeding the trigger-pull, the better the trigger feels. Once the engagement area is okay, it’s easy to set this screw to stop the trigger immediately following trigger release.
With that done, I put the cover plate back on the trigger and shifted my attention to the S331 sight. By the way, Robert of Arcade explained in a comment that the S331 sight was actually made by Mossberg and not by Williams, as I originally said in Part 1. I changed the maker to Mossberg in Part 1, and now I’m telling you.
The rear sight on this rifle was loose when I examined it, so I removed it from the rifle and disassembled it for cleaning. Most of the parts are aluminum, but a couple are blued steel and suffered from rust to the point that there were pits left on their surfaces after the rust was removed. The detents are very crisp and easy to feel as you make the adjustments. This is a simple peep sight assembly, but it works very well and adjusts precisely, which is all you can ask of a sight.
Once the sight was clean and back on the rifle, I put the barreled action back into the stock. I had to use the old broken safety switch because the replacement I have is slightly too large to fit the hole. I’ll trim it down in a separate session so the gun has a complete safety switch. For now, I’ll just keep the rifle off safe.
How does it look?
Because the bulk of the deep rust lies below the stock line, the deep pits that appeared from cleaning do not show. What was above the stock line was mostly just surface rust that’s now completely gone. The metal on this rifle now appears to be 80 percent or better. The stock finish is still flaky and needs to be taken down all the way with sandpaper and reapplied, but it doesn’t detract from the rifle’s appearance.
And the trigger?
The trigger now breaks at one pound, even. It’s glass-crisp, and you would swear that it releases at just a couple ounces if you didn’t see the trigger-pull gauge. I think the owner will be amazed at the transformation this rifle has undergone.
Yet to come
I won’t bore you with the other mundane jobs like the safety and the stock finish, but I’ll test this rifle for accuracy. So, there’s one more report yet to come. We already know the velocity is in the right ballpark — 656 f.p.s. for a 14.2-grain Daisy pellet on a 90-degree day. But I want to show you the accuracy these old rifles can give with modern pellets.
by B.B. Pelletier
El Gamo 68 is a futuristic breakbarrel from the past.
I’m sure many of you imagine that I’m immersed in airguns all the time, which is true. That my office is filled with all sorts of models (it is) and that my workshop bench is strewn with parts of projects in process. There’s just one problem with that view. I don’t have a workshop. When I really need a lot of room, such as for today’s report, I usually move to the kitchen, where I do my work on that time-honored bench — the kitchen table!
The other thing most readers don’t appreciate is how whipsawed I am with time. I can’t afford to spend a week or even two days on a project anymore. Back in the days of The Airgun Letter, I had one month to crank out the stories that are now written in about four days! If I spend more than three hours on a project before starting to write about it, I’m working on a 12-hour day because the writing and photography take so much more time than the actual testing. And so it was with some trepidation that I approached today’s report, which is a disassembly, evaluation, cleaning and lubrication of my Gamo 68 breakbarrel air rifle.
I wanted to do this because the 68 shoots very suddenly. It doesn’t vibrate like many spring guns, but the thump when it fires is very heavy — way out of proportion with the power of the gun. The trigger is very heavy, and I wanted to see what might be involved in bringing it down. It’s crisp enough, just too heavy for the release.
Because of the potential time element and the fact that I have no room for another disassembled airgun, I studied the rifle carefully for two months — the way a diamond cutter examines an important stone. And with all that study, I still did not recognize the way the gun is assembled. But one look at a schematic sent by David Enoch showed me what to do.
Only three screws have to be removed to take the action out of the stock. That’s no different than any other breakbarrel, but the location of the third screw is certainly different! It’s at the back of the spring tube.
This photo shows the action out of the stock. One extra screw was removed. The one below the triggerguard does not hold the action in the stock. It’s one of two screws that hold the trigger unit to the stock, and it doesn’t have to be removed to get the action out of the stock.
With the action out of the stock, you have access to disassemble the mechanism and do what I ended up doing to the rifle. The trigger is really a complex bullpup unit that’s entirely separate from the barreled action. By “bullpup,” I mean that the trigger blade does not directly contact the sear. It’s located many inches forward of the true sear and is connected by a long lever inside the trigger unit. If I want to improve the trigger-pull beyond what simple adjustment can do, I need to remove this unit from the stock to get access to the pins and levers.
I decided to leave that task for another day, as working on the powerplant was all I had time to do in this session.
You’re looking down into the aluminum stock that holds the spring tube. The trigger unit runs from almost all the way on top, where the trigger blade is located, to all the way on the bottom, where the true sear releases the piston. It’s a complex bullpup unit that must be removed as a unit for work. You can see the steel channel that holds all the trigger parts.
Because of the way the Gamo action is designed, I could set the trigger aside and go to work on the powerplant. The end cap is held in the spring tube by a single large pin that must be drifted out. The action was installed in a mainspring compressor for this next step.
Here you see the barreled action in the mainspring compressor with the large pin drifted out. The pin is on the table, next to the hammer handle. The spring tube is ready to come apart.
Moment of truth
Taking a spring-piston powerplant apart for the first time is always a surprise. You never know how much compression the mainspring is under, even when relaxed, and how far it will come out of the gun before it’s fully relaxed and the gun can be removed from the mainspring compressor. It was a real surprise this time, for the spring came out several inches before fully relaxing. If I had just drifted the pin and tried to hope I could hold the end cap with my body, I could have broken bones!
Like a python that swallowed a telephone pole, the mainspring just kept coming out of the spring tube until it was this far! As you can see, I didn’t have much more room on my adjustment screw.
Once tension is off the mainspring, the rifle can be removed from the compressor. The end cap, spring guide and mainspring can now be removed. The piston, though, is still held in the rifle by the cocking link. You must disconnect the link from the piston before it will slide out of the gun.
The 68 has an articulated cocking link, and I noticed a spot at the front of the cocking slot that was enlarged for the removal of the cocking link. That told me that I did not need to remove the barrel from the action to disconnect the link from the piston. Just line up the link end with the enlarged hole, and the end pops right out.
The cocking link is two pieces.
The end of the link can be removed from the spring tube through the enlarged hole at the end of the cocking slot. The two-piece cocking linkage helps you do this.
The mainspring and piston both told me this gun had probably never been apart before. The grease looked like factory grease, and there were many years of accumulated dirt and grime on all the parts.
The piston has a leather seal that looks brand new. It was a bit on the dry side. After I assembled the rifle, I lubricated it heavily. I’ll continue to do that many times over the next few months, until I’m satisfied that the leather is oily and supple once more.
Leather piston seal looks good.
The piston itself is a very strange duck. It has to be, because the trigger is autonomous from the powerplant. There’s a window on the side of the piston at the rear where the sear catches it when the gun is cocked.
Here you see the entire piston, which is a machined steel part. The rectangular window at the end of the piston skirt is where the sear catches and holds it when the gun is cocked. Only the piston seal and the machined section at the rear touch the inside of the spring tube, so that’s where the moly lubrication goes.
The inside of the spring tube was as dirty as the piston and mainspring. I put paper towels over the end of a long-bladed screwdriver, dipped the paper in alcohol, and cleaned the inside of the spring tube and compression chamber. This would also be the time to remove any burrs from the cocking slot, but there weren’t any on this one.
After the entire powerplant was cleaned, I examined that long mainspring. After all those years, I thought it had to be canted — and it was, though not as much as I’d imagined. Rolling it on a flat surface revealed a wobble at one end, which translated to a jolt during firing. Hopefully, I had a suitable replacement.
I found several possibilities, but the best one proved to be a replacement spring for a TX200, of all things. It’s a special spring Jim Maccari made some years ago and it has collapsed coils in the center and at one end. As you can see in the picture, it’s a lot shorter than the spring that was in the 68. The wire is thicker, but there are so many fewer coils that I knew it would fit. The fit inside the piston was about the same as the factory spring, and the fit on the spring guide was tighter. So, this is a good replacement.
Factory spring above, replacement below. The new spring will certainly be under less compression when the gun is not cocked!
I coated the new spring with a thin layer of black tar and inserted it back into the piston. The front and rear of the piston were then coated with a heavy layer of moly grease and installed back into the spring tube. The cocking link was inserted back into the enlarged hole, where it contacted the piston for cocking.
The spring guide was coated with moly and slid inside the mainspring as far as it would go. The end cap was placed over the end of the spring guide, and the barreled action was installed in the mainspring compressor, once again. This time, the amount the spring stuck out was drastically reduced.
The spring guide is steel. It was coated with moly and slid back inside the mainspring.
The new mainspring has just begun to compress. It’s a lot shorter than the old one!
The gun went together without a hitch! And that was when I noticed for the first time that the entire job from start to finish had taken me only one hour — including photos! That’s as fast as I could tune a TX200 (assuming I would, which would never happen), and it doesn’t require a mainspring compressor. This wasn’t the time-killer I thought it was going to be.
How does it shoot?
The rifle cocked with 22 lbs. of force before this tune. Now it takes 28 lbs. to cock it, and the final sear lockup takes a final crunch that wasn’t there before.
The gun fires with 70 percent less jolting than before, but its just as quick as it was before the tune. The feel of firing is atypical of a lower-powered breakbarrel, just as it used to be. I can now feel a little vibration in the powerplant that I think was previously masked by the heavy firing jolt.
I still don’t know the gun. It will take a session of velocity testing and shooting for accuracy before I can finish this report. Since I’ve already tested the gun extensively before, I’ll combine both of those things in the next report.