Archive for August 2012
by B.B. Pelletier
This report was requested by blog reader Wulfraed in one of his comments.
For the benefit of those who shoot airsoft guns, the BB I am addressing today is the steel BB that historical BB guns shoot — not the 6mm plastic ball that Asian-made airsoft guns started using in the 1970s.
The first BB used in an air rifle was BB-sized lead shot used by shotgunners. In the day when it was popular (the 1880s), shot was sold in bags in hardware stores and came in various numerical and letter sizes, including sizes B, BB and BBB. BB shot was supposed to be 0.180 inches in diameter and weigh more than nine grains.
At the turn of the 20th century, Daisy reduced the size of what they always called air rifle shot to a lead ball 0.175 inches in diameter. That saved them lead and also went faster because it was a lighter ball.
In the 1920s Daisy discovered that some boys in Minneapolis were using steel ball bearings that they were salvaging from a reject pile behind the American Ball Company. They checked the sizes of the balls they wanted to shoot by dropping them through the bores of their shot tubes. If they passed through, they were fired. If they stuck, well, a huge influx of stuck steel balls in shots tubes was what got Daisy’s attention in the first place.
Long story short, Daisy bought American Ball and started making their own steel air rifle shot. It was sized 0.171-0.173 inches, nominally. They had to change the size and design of their shot tubes to accommodate the new shot, and some time late in the 1920s BB began rebounding from hard targets with great force — something the soft lead balls had not done. This started the mothers of American warning against shooting your eye out.
So, how do they make a perfectly round sphere of steel? You can’t afford to cast steel into balls, nor can you afford to forge or swage the balls — again, because of economy.
So, how is it done? Pretty simply when you understand how it works.
Ever roll a piece of clay into a ball? You hold it between your palms and rotate each hand in the opposite direction. Has anyone not done this as a child?
So, short of being Superman, how do you roll a piece of steel into a ball? Well, it helps to have hands of steel, and that’s exactly how they do it.
The first step is to get a piece of steel that’s close to the right size, which means the same mass as the ball (BB) you wish to make. An easy way to do this is to take a spool of steel wire and cut it into precise chunks, then feed them between two hardened steel plates that have spiral grooves cut in their mating faces. Each plate is several feel across.
Each large spool of steel wire weighs about a ton (2,000 lbs.). These are fed into a precision wire cutter that slices off exact chunks the right size to make one steel BB. You can see by the amount of wire on hand that they intend making millions!
This wire-slicing process is called heading; and if it isn’t done precisely, the finished BB may be spherical, but have one or more small flat spots in its surface. This defect comes from improper heading and is very difficult to sort out during the manufacturing process.
The plates are smooth on their surfaces, except for the spiral grooves. The chunks fall into the grooves as the two plates rotate in opposite directions — like your hands rolling a piece of clay into a ball. The spiral grooves catch the sharp edges of the cut steel pieces and roll them around as the plates turn. Once the pieces fall into a spiral, they cannot get back out, so they remain in the groove, tumbling and rolling around.
The spirals also become more shallow as they spiral in the plates, so the balls can’t stop tumbling and rolling, and they cannot back out. As the steel plates turn, the balls are forced in the same direction, which makes them smaller and rounder as they go. In the end, most of them roll into near-perfect spheres — just like the clay balls you rolled in your hands.
I would like to show you these steel plates; but this part of the BB-making process is considered proprietary, and I was not allowed to photograph it.
These balls are not yet BBs. But back to this rolling process a minute. The manufacturer feeds thousands of chunks of steel each hour into each set of plates they have working, and when the chunks are rolled into near-perfect balls, they then drop out of the plates. Some kinds of imperfect balls will also drop out, but they’ll be caught later on.
So, thousands of round balls per hour come from each set of rotating steel plates. The balls that exit each set of plates are carried by conveyor to a metal-plating machine where they receive a very thin coating of rust-inhibiting metal. As raw steel balls, they would start to rust almost immediately; but when uniformly plated with copper or zinc, the steel is sealed from the air and the BBs can last for years without oxidizing.
Once they’re plated, they’re sorted by several processes. One process rolls them down a spiral channel where the smooth BBs pick up speed and roll up on the sides of the channel from centrifugal force — much like a bobsled going downhill, while those that have some rough spots roll slower and more bumpily, staying in the center of the slide where they eventually drop through holes and are eliminated. What passes this test are finished BBs.
They may be graded by size at this point, by passing over holes of different sizes and then being sent to different places for packaging into different products. If any are too small or too large, or if they have any flashing or other imperfections, they’ll usually be caught in this last test.
Start to finish, the process takes some time, measured in hours because of queing and transit time. The actual manufacturing time is much less. Crosman runs three shifts a day and cranks out 4 million finished BBs every 24 hours.
Daisy used to make its BBs this way, or by a process that was very similar, but they have now moved the manufacture of their BBs offshore. They receive 55-gallon drums of finished BBs from their foreign manufacturer, which they then sort before packaging. Their BBs are extremely uniform, so the process works regardless of where the BBs are made.
by B.B. Pelletier
This is the second part in our series of bending airgun barrels.
Settle in, boys and girls, for this report will be long and involved. Today, I’ll begin the quest to bend or straighten an airgun barrel to fix many problems.
I’ve waited to do this report until I could give you a barrel bending (straightening) fixture that anyone could build for very little money. I’ve not built mine yet, but the design is so simple that I have complete faith it will work. And if it doesn’t, there’s always the crotch of a tree or the joint in a picnic table that’s currently being used by many people to do the same thing. I think my fixture gives you a lot more control over the process, so let’s see if it works.
First, we need a bent barrel. I intentionally bent an airgun barrel for you. I bent a breakbarrel by firing the gun with the barrel broken open, as in the common excuse –”My hands slipped while I was cocking the gun!” (everyone who ever did this uses that excuse).
The gun I’m working with is already marked for destruction. I thought that before it goes away, it might serve one last honorable duty. It’s a .22-caliber rifle and I selected .22-caliber RWS Hobby pellets for this test. We don’t care about accuracy in this test — just where the pellets are landing with respect to the scope setting. Don’t ask what kind of gun it is — the model is unimportant. I removed the anti-beartrap device so the barrel would close when the trigger was pulled, so this rifle was initially safe as it was designed and built, but I circumvented it.
I first photographed the gun with an obsolete CenterPoint Optics 3-9×40 AO scope mounted. CenterPoint scopes are no longer made by Leapers, so this scope is now unavailable, but it has a mil-dot reticle that became important in today’s test.
Here’s the test rifle with its scope mounted. This is before the first shooting test.
The first thing was to establish that the rifle could hit the target using the test scope. I chose to use 10 meters for the test distance; because at 25 yards, with the way the pellet would rise after the barrel was bent, I could wind up with more holes in the walls of the house. Edith tells me that’s a bad thing!
The first shot was from 15 feet. I shot in the standing position and supported my hand with the door jamb of the garage door. Because I’ve rearranged my garage, I have to sight-in at 15 feet instead of the old 10 feet. I shot at the upper bull on the target, and the pellet hit just below the lower bull. The rifle was striking the target about 3-1/4 inches below the point of aim at 15 feet. Then, I backed up to 10 meters and shot again.
At the 10-meter bench with the same scope setting, I shot at the top bull again. A three-shot group was low and to the left of the aim point. It was not as low as it was at 15 feet, which is to be expected. So, I adjusted the scope up and to the right to correct it.
The first shot after the scope was adjusted was at the lower bull. The pellet landed a half-inch low and a quarter-inch to the left of the aim point. A second scope adjustment put the next pellet into the center of the targeted bull. Four more shots completed a 5-shot group.
The picture that follows documents everything you’ve just read.
I then took the scope off the rifle before bending the barrel. This is a very stressful procedure, and there’s no reason to subject the scope to this kind of punishment. However, this is a place where bias can enter my test, because taking the scope off the gun and remounting it again will definitely cause the aim point to shift some. I hope to show, however, that it moves so far upward that it cannot be blamed on just removing and remounting the scope, alone.
Bending the barrel
What I am about to describe is a way of definitely bending an airgun barrel. Don’t do it, because it can also break the stock. If your fingers are in the way when this is done, it’ll cut them off. I broke open the barrel until the gun was cocked, then pulled the trigger with the barrel in the open position. Remember that I had already removed the anti-beartrap mechanism, so now the gun would fire with the barrel in the open position.
The piston moving forward acts on the cocking link to slam the barrel shut so violently when the gun fires that the barrel bends upward every time. This is a classic abuse of an airgun. If I’m ever called as an expert witness in a liability case, I will say that this was done intentionally — because in every instance I’ve investigated, it was.
Now you can see the results of doing what I just described. The barrel is bent upward, starting at the end of the baseblock — a classic case of a slam-fire in a breakbarrel.
You can clearly see that the barrel has been bent upward in this photo.
The stock was not broken this time, but one of the two stock screws was pulled deeper into the wood on one side of the forearm. I can see the barrel is bent without looking for it, so I’m now very concerned that the gun will shoot above the target when I remount the scope.
Once the scope is back on the rifle, I return to 15 feet from the target — and this time, I drew a new aim point below the target at the bottom of the cardboard target backer. The same aim point was used for all shots in this part of the test.
Then I took that first shot. The pellet struck the target 4-3/4 inches above the aim point. I was on paper, so I cranked in all the down elevation adjustment the scope had, and the second pellet dropped about 2 inches below the first. It was still 2-3/4 inches high at 15 feet. I felt safe, so I backed up to 10 meters and shot off the bench.
The first shot from the bench landed 7-1/2 inches high at 10 meters. It was perilously close to the target clip that holds the target to the backstop, so I used the mil-dot above the crosshairs for the next 5 shots. I now had a group on paper at 10 meters, but it was so far above the aim point of the scope that it was completely useless. At 25 yards it would be many inches higher than it was here. So, the barrel is definitely bent upward and has to be dealt with before the gun can be used again.
This target documents how the same rifle shot after the barrel was bent. The aim point at the bottom proved not to be low enough when I backed up to 10 meters, so I had to use the first mil-dot above the crosshair intersection to hold on the aim point. I was aiming about 9 inches low at 10 meters — and was still almost off the top of the target!
Now, I have an airgun with a documented bent barrel on my hands. You absolutely cannot see the bend by looking through the barrel, as I’ve been told. At least I don’t see it. But the results on paper and even just looking at the gun tells me the barrel is definitely bent.
I have to straighten this barrel, obviously. My next step will be to build a barrel bending and straightening fixture that’s cheap and easy to make. I’ll use the fixture to straighten this barrel and show you the results of the job after I’m done.
After that, I have a BSF S70 rifle that currently shoots too high with the aftermarket peep sight that’s installed. If my barrel bending/straightening fixture works as expected, I will apply it to that gun and show the results.
The bottom line of this report will be a way for you guys to bend your barrels as required, with complete control and little risk of damage. I’m as new to this as are many of you, which is why I’m doing it for all of us.
by B.B. Pelletier
Last week, our new reader, Cantec, mentioned that several gentlemen were advising the use of corn oil for lubricating the compression chambers of spring-piston airguns. I know exactly where this recommendation came from and how it should be viewed, and I wanted to share this with you today.
Yes, I’m talking about common corn-based cooking oil. Wesson oil is the most popular brand here in the U.S. Why would anyone recommend using corn oil in a spring-piston airgun? I want you to know the entire truth so you don’t make any serious mistakes with your guns.
Good old corn oil that’s most often used for cooking has also been used to lubricate some spring-piston airguns.
In my role as a firearms enthusiast, I used to put WD-40 on all my guns. It smells so good and guns always look so nice after they have been wiped down with it. So, when the Army sent me to Germany for four years, I sprayed WD-40 on all my guns before storing them in my mother’s attic, thinking I was protecting them against the ravages of time. What happened, instead, was that the WD-40 dried out and left every gun covered with a thick coating of yellowish residue that proved nearly impossible to remove. Only more WD-40 would dissolve it, and in one case the silver plating on my collectible second generation Colt 1851 Navy cap and ball revolver was destroyed! Each gun took weeks to clean, because the residue had gotten into all the cracks and tight places and had to be scraped out with tools.
Several years after that experience, I joined an horology club and attended their meetings for about a year. These are guys who fix watches and clocks, and they had one thing to say about WD-40. Don’t ever use it on a clock! They knew all about the yellow coating it leaves, and several members had horror stories about removing it from clock gears. Apparently, not even ultrasound tanks can remove all of it.
Before you rise up to defend WD-40, know that I use it, too. For certain jobs, it can’t be beat. But not for protecting the finish of a gun. Use Ballistol for that.
What does WD-40 have to do with corn oil? Everything. Like WD-40, corn oil dries and leaves a waxy film on anything it comes in contact with. And that’s why it was originally recommended for spring-piston airguns. Not all spring-piston guns, you understand. Just the ones from China.
Duane Sorenson, who used to work at Compasseco in the 1990s, recommended corn oil for all his Chinese guns because of the waxy buildup. He reasoned that the wax filled in the rough machining marks left inside the cheap Chinese compression chambers, eventually building up to the point that compression increased. He was an active proponent of corn oil in spring guns, and I think many thousands of shooters were told by him to use it.
Duane also said the flashpoint of corn oil was very high, so using it would stop dangerous detonations. As far as I was able to test for that, it did seem to work. But — and this is the point of today’s report — corn oil is not recommended for a sophisticated spring-piston airgun powerplant. The current crop of Tech Force guns do not have compression chambers rough enough to benefit from its use.
Time is the criterion
Duane was advising corn oil for airguns like the B3 underlever and the TS45 sidelever. Those guns really did have rough compression chambers that could benefit from a product that infilled their machining marks. But at the same time he was recommending corn oil, Sorenson was also pushing their Chinese manufacturing partner to better finish the insides of their compression chambers. The result was the Tech Force 36 underlever, which was very smooth inside, and later the Tech Force 99, which was even better.
But while this improvement was happening, Duane was still selling lots of the older and less expensive Chinese spring guns that were still very rough. So, he continued advocating corn oil, even as the many of the guns he sold were getting better and had less need for it.
I tested it
Duane was so insistent on corn oil being a miracle-product that I bought a quart of the stuff and began experimenting with it. That was how I learned that it doesn’t detonate. While I was testing it, I was unaware of why corn oil was being recommended and the fact that many of the more modern chinese airguns didn’t need it.
I conducted several tests using corn oil for The Airgun Letter, but frankly I never got the kind of results Duane told me to expect. Part of that was because I was probably testing it on the wrong guns and part was because I wasn’t using it as much as Duane did. I never saw the long-term effects he told me about.
I expected to see an increase in velocity and a decrease in the total velocity variance. The velocity never increased as much as I had thought, but the shot-to-shot variation did decrease somewhat.
What about corn oil today?
This is the reason I wrote today’s report. Do not use corn oil in any modern spring-piston airgun! Corn oil is meant to solve a level of manufacturing crudeness no longer seen in modern airguns. Like many other things, time has changed the game. We no longer put oatmeal in our car radiators to patch small leaks, and we certainly no longer lubricate spring-piston compression chamber with corn oil.
Just as you don’t want a buildup of hard yellow film on the outside of your airguns from dried WD-40, you also don’t want the waxy buildup from corn oil on the inside. Use the products that are recommended for the job, like a proper grade of silicone chamber oil for the compression chamber of your airguns.
by B.B. Pelletier
Blog reader Kevin inspired this report with a comment he made on Friday’s blog. He wondered whether my exposure to nearly all the airguns in the world, both past and present, has inspired me to own any one gun in particular. But it also comes from my visit to Leapers this past week (which I will be sharing with you very soon), because that thrust me into the world of manufacturing, again. I still remember a lot from my time at AirForce Airguns, but visiting Leapers and speaking with all their product developers brought technical things back into sharp focus, again.
There was also a comment last week from someone who stated outright that a spring gun is far simpler than a precharged pneumatic. When I read that, it didn’t sit quite right with me, so I thought about it for awhile until I had worked it out. And this report is the result.
So, today’s question is this: Which is simpler — a PCP or a springer? The answer may surprise you.
A spring-piston gun is far less cumbersome for a shooter to operate — I think we can all agree about that. All you do is cock it, load a pellet and you’re ready to go. With a precharged gun, there’s the complexity of the gun, itself, which is pretty much on par with the springer in most cases. Only the repeaters are more complex because of how their magazines or clips are loaded with pellets and then how they’re loaded into the guns.
But a precharged gun brings with it the need to put air into the gun at some point. And this is where things can get very complex. Sometimes, they’re not as bad as shooters realize or imagine. The part about filling the gun can be no more involved than it would be to take the pumping function that all multi-pump pneumatics have…such as the Sheridan Blue Streak…and separate it from the gun. That was what was behind the Benjamin Discovery precharged air rifle, and it’s the reason the Discovery is an order of magnitude less complex than all other PCPs on the market.
The Benjamin Discovery is simpler than other precharged airguns because of its lower fill pressure. One version comes with a hand pump that can easily fill the gun with little effort on the shooter’s part. Think of it as a more powerful and more accurate Sheridan Blue Streak with a separate pump.
The common perception among airgunners is that a PCP is more complex than a springer because of the need for special fill devices. Actually, the Benjamin Discovery and all other guns that use a Foster quick-disconnect air fill coupling have fixed this problem, but there are still a lot of PCP makers who aren’t yet using this type of fitting. So, their rifles are, in fact, more complex and prone to equipment compatibility problems for the buyer. But all Benjamin PCPs, all Daystate PCPs, the USFT rifles and all Quackenbush PCPs now come with the common Foster fitting. So, if informed users shop for a gun that has solved the filling problem in this way, they won’t have to deal with that issue.
AirForce Airguns recognized this fact also and created a Foster fill device for all the AirForce Airgun sporting air rifles (Talon, Talon SS and Condor), adding that company to the growing list.
And the perception problem continues, as new shooters believe that they need to own a chronograph with their PCPs, to somehow manage them. The truth is that you can manage the shots in a PCP just fine by shooting the gun at great distance and stopping whenever the shots start to scatter. That tells you the maximum number of shots you get per fill if you’re shooting at that distance. If you shoot closer, there are more shots per fill before the groups enlarge. But that isn’t how the articles and reports read, and people are blinded by the perceived need for additional expensive technology. I recommend owning a chronograph because it helps you know your gun better, it isn’t absolutely required.
Spring guns, on the other hand, are perceived as being simple and easy to understand. The only complexity that most shooters know about is the need for some skill in holding the gun when it fires. A PCP shoots accurately regardless of how it’s held, but a spring gun can be very sensitive to slight changes in the hold. Other than that, though, the springer is thought to be dirt-simple.
Manufacturers see the spring gun/PCP world exactly in reverse. It’s the PCP that’s simple and straightforward to make, and the spring gun that requires a lot more machining operations and special tooling to complete. The PCP is a reservoir connected to a barrel, with a valve in between. It’s a simple, straightforward arrangement.
A springer has the barrel that must be held in a baseblock to withstand the shock of the firing cycle as well as deliver the small puff of compressed air generated by the piston to the rear of the pellet. While a PCP valve is about as complex as an entire spring-piston powerplant, nothing in it is under anywhere near the stress from an overly powerful mainspring or the heavy hammer-blows of the piston. Where the trigger in a PCP holds back 6-10 lbs. of striker-spring force, the spring-piston trigger might hold back 150 lbs.
A spring-piston gun needs a lot of very strong components to withstand the hammering of the piston. A PCP can be made of lighter components. There are heavy PCPs on the market, but I invite you to examine the Benjamin Discovery and all the AirForce Airgun sporting rifles to compare the power that lightweight PCPs deliver, as opposed to what super-heavyweight springers can do. And I’m saying nothing about accuracy, where the PCP wins every time.
We’re discussing an airgun manufacturer’s perspective of the two types of powerplants, and there’s one weak spot in the PCP’s design. It has to be built to hold air under high pressure for a long time, and air under pressure is hard to hold. Some companies find this to be a very daunting challenge, because they don’t understand the need for absolute cleanliness in the manufacturing area, or they select materials that are known to have porosity issues, or they use dull tooling (not changing it often enough) or they’re just sloppy in their assembly. I worked for three years at AirForce Airguns and was intimately familiar with every step they took to protect the long-term integrity of their compressed-air reservoirs.
I own three AirForce guns, and all are stored at full pressure all the time. In the past 12 years, I’ve never had a single issue of leaking. I’m not saying it doesn’t happen, because it sometimes does. But compared to the PCPs from certain other manufacturers that have some or all of the problems I just mentioned, AirForce Airguns has none of them.
I watched Crosman build their first Benjamin Discoveries, and they had the good sense to do a 100 percent testing of their guns holding air before shipment. They continued doing this until they knew they had a positive handle on the build process. That’s how a good company enters the PCP market! In contrast, there have been more than a few boutique PCP builders who learned as they went and let their customers be the quality control. I won’t name any names, but this practice is what gave PCPs a black eye.
Do spring guns have similar weaknesses? Yes, they do, but because of how they work, they can often still function when the manufacturing is flawed. Guns full of metal shavings make it to market, and their new owners are none the wiser. That would kill a PCP, but a springer will still shoot when the compression chamber is filled with metal shavings and the piston is embedded with nails! Comparing a springer to a PCP is like comparing a longbow to a top-of-the-line crossbow. The longbow is simpler and will work under less favorable circumstances, but the crossbow will outshoot it every time and in every way.
The next time you hear someone say that a springer is simpler than a PCP, ask yourself what they’re really saying. Because you may not want all the shortcomings that accompany the “simpler” design.
That concludes this report, but I have more to say. I wrote today’s report because I felt that it would be good to explain the full ramifications of an issue that we airgunners often assume to be an open-and-closed case. I sometimes delve deep into the technical aspects of airgun performance in my reports, and I think it can lead readers astray. My comment above about not needing a chronograph for the enjoyment and operation of a PCP was an attempt to bring this out.
I am soon going to start another test that will be both long and technically involved. The results should prove interesting, no matter what they are, but I’ve had to choose only one of several possible ways to conduct the test. We’ll learn some things, but the possibility exists that bias will also be present, because I cannot test everything. I’m using today’s report to get your minds into an analytical mode, but I don’t want to leave any of the new readers behind.
The object of today’s report is that every question should be viewed from several different perspectives, because sometimes the things we think are obvious are not really what is happening.
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
Today, we’ll look at the accuracy of my Beeman R1 air rifle, and I must say that I remembered the rifle exactly as it is. It is very sensitive to hold, but also very heavy, at 11 lbs. in the test configuration, which stabilizes the gun to a great degree. Compared to the twitchy over-bore spring guns of today, shooting my detuned R1 is like driving an old family car!
I sighted-in with 15.9-grain JSB Exact domes because I thought they would turn out to be the best pellets. Even though they fit the breech loose, I felt they would surpass all other pellets. Let’s see how they did.
The distance is 25 yards, and I’m shooting from a rest, using a classic artillery hold where the back of my off hand touches the front of the triggerguard. I did try a group with a different hold, but it opened right away, reminding me that I know this rifle quite well.
The first group of JSBs contains a nice 8-shot group at the center of two shots that appear to be fliers. They aren’t fliers, though, because I held the rifle the same for every shot. It’s possible I didn’t relax enough for those two shots, which is why I say the R1 is sensitive to hold. As a powerful breakbarrel, you expect it to be hold-sensitive.
The first group gave me some confidence in this pellet, so I adjusted the scope, shot a couple rounds to settle things and fired a second 10-shot group of JSB Exacts. This time, all 10 shots landed in a group measuring 0.642 inches between centers. My hold while shooting this group was more relaxed than the first.
Next, I decided to try some Crosman Premiers. When this rifle was new in 1994, they were the best pellet on the market. Ten shots gave a very round group that measures 0.683 inches between centers. That’s ever-so-slightly larger than the second JSB group, so I feel these two pellets shoot about the same.
I then tried the H&N Baracuda Match pellet that I don’t remember ever trying in my gun. I know they’re going slower — I can hear the amount of time the pellet takes to get to the trap. I didn’t know what to expect, but boy does my rifle like this pellet! The first 8 went into a very small group, then I rushed shot 9 and got a pellet outside the group. It wasn’t a flier, it was a mistake in technique, pure and simple. Shot 10 went into the tight group, and I ended with a group that measures 0.684 inches between centers, with 9 of those pellets in 0.54 inches.
I feel the H&N Baracuda Match pellets turned in the best performance overall. So much so, that after the session ended I adjusted the scope so this pellet hits the point of aim at 25 yards.
The light, crisp Rekord trigger contributed a lot to the success of this rifle. It releases so well that the rifle isn’t affected by anticipation. Before I can hope for the gun to shoot, it already has.
The R1 recoils forward a lot. That’s due to the heavy piston. But most of the vibration has been eliminated. That’s something I wish the rest of you could experience. It’s so satisfying to shoot an air rifle like this because if feels so RIGHT.
What’s the bottom line, here? Well the R1 is still a fine spring air rifle with many classic features in its favor. Being a springer, it’s difficult to shoot well, but it’s capable if you do your part. It has one of the finest triggers on the market, and there’s nothing more I can say about that. But the R1 is also a very large rifle, and often I want something a little smaller so I can shoot all day without straining.
The tune that’s on the gun now is very light and easy to deal with. It makes the R1 feel like an R9 in all ways except size and weight. Now that the test is finished, this one will go back to the closet…but I know it’s sighted-in. If I call upon it in the future, it’ll do the job.