Airgun lubrication — pneumatics

by Tom Gaylord, a.k.a. B.B. Pelletier

Airgun lubrication — spring guns: Part 1
Airgun lubrication — spring guns: Part 2
Airgun lubrication — gas guns

This report addresses:

• What is a pneumatic?
• No. 1 lubrication need.
• A short pneumatic history.
• Which oil to use?
• Other lubrication.
• Wipe down.

This report was written for blog reader Joe, who asked for it specifically; but I know that many of our newer readers also found the information useful. Today, we’ll look at pneumatic guns. There are 3 very different types of pneumatic airguns — precharged, single-stroke and multi-pump — but I think they’re similar enough to cover all of them in the same report.

What is a pneumatic?
Pneumatic airguns store compressed air for one or more shots. Single-strokes get just one shot per fill and so do most multi-pumps, though there are some that do get multiple shots. Precharged pneumatics (we shorten the name to PCP) get many shots per fill.

Big bores, which are always PCPs, get the fewest number of shots per fill, but the smallbores (.177, .20, .22 and .25) get many. How many depends on the output power of the gun and the amount of compressed air that’s available (i.e., the capacity of the air reservoir).

No. 1 lubrication need
The most important reason to lubricate a pneumatic of any kind is to seal the gun. This is similar to gas (CO2) guns; but since pneumatics use air — which is thinner than CO2, their lubrication is extremely important. The seals in the guns are all sized to their jobs. In the case of o-rings, they sit in channels that assist in their sealing role; but without the right lubrication, all would be lost.

A short pneumatic history
Pneumatics are the oldest type of airgun, and their technology has evolved over more than five centuries. The first pneumatic guns used leather seals in all places to seal the reservoir as well as sealing the firing valve.

As time advanced, airgun makers learned how to lap (polish until smooth) valve faces of animal horn that is much better and less porous than leather. These valve faces would be hand-lapped to match the exact surface of the metal (brass or bronze) valve seats to which they were fitted. When the lapping job was finished, these valves would hold air much longer than leather. Leather was still used to seal the junction around the threads of the reservoir, so the guns still leaked down — but the amount of leakage was reduced by a significant amount.

[Note: Airgun designer John Bowkett determined decades ago that precisely machined stainless steel valve faces and valve seats work best of all, providing there’s enough lubrication and the machining is correct. The contact surface of this type of valve is extremely fine and narrow; but if it’s perfect, this valve will be very controllable. The downside is that valves made this way are still extremely labor intensive.]

Leather seals and horn/brass valves were still being used in big bore PCP airguns up through the 1920s. Smallbore PCPs didn’t come into being until 1980, when Daystate converted one of their tranquilizer dart guns into a .22-caliber sporting rifle they called the Huntsman. Daystate was the first company to build a modern PCP; and when they did, synthetic materials were both available and far better suited for pneumatic valves. At the same time, o-rings in properly cut channels provided the remainder of the sealing solution in place of leather — and the modern PCP was born.

Synthetic seals are less porous than animal horn and last far longer. They’re not as hard as stainless steel, so the mating surfaces of the valve do not have to be machined as precisely (they have a little give to accommodate slight imperfections in the valve seats). Synthetics make the modern PCP possible. And lubrication is what keeps PCPs sealed almost forever.

Leather seals in other pneumatics
Leather has been used for the peripheral seals in multi-pump pneumatics up to as recently as the 1950s. Just like the leather seals of old, the problem has always been how to keep the leather seals lubricated so they remain soft, pliable and doing their job. Oil was used originally in these airguns in the late 1890s. But times change and today we have better lubricants. Petroleum jelly will stay on the job many times longer than straight oil, so even the leather seals in your vintage multi-pumps can be lubricated for a long time.

Which oil to use?
That brings us to the big question of the day: Which oil to use? In this instance, there isn’t just one answer. For PCPs, the right oil needs to have a very high flashpoint so it isn’t prone to explode when subjected to high pressure.

I know of two instances in which petroleum-based oil or grease has caused an explosion in a PCP. One was a vintage PCP reservoir that was pressurized to around 800 psi. The interior walls of the reservoir were coated with grease to trap any dirt particles that might get in during filling. This is a common practice with such airguns; but this time the person who greased the reservoir used petroleum grease instead of organic-based (animal) grease. The reservoir blew apart at the soldered seam! Fortunately, no one was hurt.

The other instance was one I got from a news story, and the person involved was, unfortunately, killed when his modern PCP reservoir exploded. The article said he had apparently introduced regular household oil into the reservoir.

On the other hand, I’ve safely oiled PCP tanks hundreds of times with a couple drops of Silicone Chamber Oil through the air intake port. I put several drops into the fill port before the gun is filled. When the air blows in, the oil is atomized and gets on all the sealing surfaces inside the reservoir and valves.

The oil to use in a PCP is silicone chamber oil. For single-strokes and multi-pumps, the answer is different. For either of these types of pneumatics I use Crosman Pellgunoil. Neither of these types of pneumatics are pressurized nearly as high as a PCP, and Pellgunoil always does the trick.

Can other oils be used instead of Pellgunoil? Certainly. I’ve used Gamo Air Gun Oil in my single-strokes and multi-pumps for many years. I use it exactly as I do Pellgunoil for single-strokes and multi-pumps, but I do not use it in any PCP guns.

The thing about multi-pumps and single strokes is to keep their pump cups sealed and working well. These are the flexible pump heads that force air into the guns, either one time or several. They tend to get hard over time and lose their ability to seal, but keeping them oiled and in use frequently will prolong their service lives. Not using a pneumatic airgun is what really hurts it.

Other lubrication
For normal lubrication of moving parts, both Pellgunoil and Gamo Air Gun oil work fine. So do most gun oils, like Remoil. What you do not want to use is silicone chamber oil for this purpose because it doesn’t have enough surface tension to lubricate properly. Your parts will rub against each other and wear.

Wipe down
As always you can use the lubricating oils to wipe down your gun’s metal and wooden parts, but Ballistol neutralizes acidic fingerprints and lasts on the surface of metal far longer than plain oil. So, it gets my recommendation for this job. It also gets the nod for the insides of all airgun barrels.

Summary
Airgun lubrication is important, for the reasons mentioned in this 5-part report. Sealing is the biggest role lubrication performs, in all cases. We’ve looked at some very specific examples of products that should be used for the reasons stated. If you decide to substitute, you do so at your own risk.


Airgun lubrication — spring guns: Part 2

by Tom Gaylord, a.k.a. B.B. Pelletier

Airgun lubrication — spring guns: Part 1

This report addresses:

• Identifing and lubricating high-stress parts
• Lubricating with moly
• Lubricating triggers
• Lubrication intervals
• Lubricating mainsprings
• General lubrication
• Preserving the airgun with oil

Well, the immediate response we got to the first installment of this report made it one of the all-time favorites. In that report, we looked just at the piston seal, which I said was half of the lubrication solution for a spring gun. Today, we’ll look at everything else.

Parts under high stress
The moving parts of a spring gun are the powerplant parts, the trigger group and either the barrel, when it’s used as to cock the gun, or the cocking mechanism if the gun isn’t a breakbarrel. When airguns were simpler and less stressed, all of these parts could be lubricated with gun oil or lithium grease. But today’s guns are stressed to higher limits and generally need something more specific and better-suited to each application.

The high-stress parts are the piston, spring guides, mainspring, cocking shoe or other linkage contact with the piston, barrel pivot bolt and the sear. Any part that has several pounds of force exerted on it should be considered a high-stress part. In a vintage gun, I still use lithium grease on most of these parts. But for the sear, where I want the minimum resistance, and for the pivot bolt, which takes the force of cocking, I’ll use a grease that’s impregnated with molybdenum disulfide. Moly is not a grease, by itself. It’s a metal that, in the form molybdenum disulfide, is a solid lubricant that bonds with metal surfaces and provides a low coefficient of friction between the treated surfaces. It’s highly resistant to wear and remains in place for a very long time.

I use products like Air Venturi Moly Metal-to-Metal Paste for this application. I also have a half-pound of molybdenum disulfide powder that can be brushed onto ferrous parts and then burnished in.

Dr. Beeman warned against using moly on triggers, as it would make them too slippery to work safely. I was an early proponent of applying moly to sears. But — and this is extremely important — the trigger has to be adjusted perfectly, or it will become unsafe. No trigger should ever rely on friction to make it safe. It should rely on geometry for its safe operation; and if it cannot depend on that, then lubricating it with moly is very unsafe. I’ve had several improperly adjusted airgun trigger sears slip and allow the guns to fire without warning, so Dr. Beeman’s caution is well-taken.

The benefits of using moly in the right places are reductions in the cocking effort and in the trigger-pull. But it takes experience to know when to apply moly and when not to. The only way to get this experience is to lubricate many airguns and watch them as they perform.

A good oil for all other applications is RWS Spring Cylinder Oil. It can be used for general lubrication of hinge points and even the mainspring, itself. Use something like this when I recommend using oil.

Lubrication intervals
Once lubricated with moly, the job will last for years and even decades before needing lubrication again. Greases like those with lithium in them are more prone to dry out and harden. They must be monitored. You can do this by eye if the greased part is visible — such as the mainspring, by looking through the cocking slot. Or, you can do it by watching the gun’s performance. This is done both by feel and with a chronograph. Here is yet another reason to own a chronograph — to evaluate the health of your spring guns.

Notice that I haven’t told you exactly how often to lubricate your guns. That’s because it varies depending on use, climate, storage and the products you use. There’s no way to accurately give a lubrication schedule with all these variables. All you can do is watch your spring guns and know when to act.

Mainspring lubrication
“They” (the people who make and sell airguns) sell oil for lubricating mainsprings. Surely “they” know best. Right? Sometimes they do, and other times they’re just copying what has gone before. If you get a new airgun (whether it is brand new or just new to you) and you note that the mainspring is bone dry, then of course a little oil on the spring would be a good thing. Nothing inside your spring gun rubs against other metal parts as much as the mainspring. So, some oil is better than no oil. But oil isn’t the best lubricant for mainsprings.

A coating of moly paste is much better. Make sure you get it around the entire circumferance of the spring wire, because the spring rubs the guides on the inside of its coils…just as the outside of its coils rubs the inside of the piston.

Mainsprings are one part where some experience comes in handy. If the gun is lower powered, like a Diana 27 or a Slavia 631, I like lithium grease the best. When it migrates forward into the compression chamber, it doesn’t detonate in these guns. Instead, it lubricates the piston seal; and because it does, I use it heavily on these mainsprings.

In more powerful guns, starting at the FWB 124/Diana 34 level, I switch to moly for mainsprings. When the grease that suspends the moly moves forward, it can cause problems, but since I lubricate very lightly with this grease, there’s seldom a problem. That is what I mean by experience making the difference.

What about gas springs?
Gas rams or gas struts, to use their colloquial terms, don’t need the same kind of lubrication as steel springs. The gas piston unit itself is lubricated internally, so you never have to do anything with it. And many of them have synthetic bearings on the outside that suspend the moving parts, isolating them from the rest on the inside of the airgun.

Nitro Piston 2 buttons
The rear of the Nitro Piston 2 piston is buttoned for friction and vibration reduction.

Moly should be used for the bearing areas of a gas spring and use it very sparingly. These units are very quick and will detonate petroleum lubricants if they’re present.

The rest of the gun
Once again, experience is needed, but it boils down to using moly on high-stress parts like the baseblock spacers on a breakbarrel and oil on the common linkage parts.

base block spacer
Here’s a telling photo. The baseblock spacers (the one that looks like a washer) on either side of the block should get some moly on both sides, as well as the pivot bolt (bottom left). The other parts, like the cocking link, only need oil.

Lubing the barrel?
The barrel doesn’t need to be lubricated. Spring guns are always expelling tiny droplets of oil and grease into the bore. This is enough lubrication for the bore if lead pellets are used. I can’t tell you what to use when lead-free pellets are fired because each material has its own requirements. I would contact the manufacturers for that. Not the dealers — the makers of the pellets.

One last thing
Finally, you’ll want to wipe down the entire gun…metal, plastic and wood…with Ballistol to protect against corrosion and damage from acidic fingerprints. This is the way to store your guns for a long time without worrying about rust. Check them from time to time and renew the external oil coat as needed.

I hope this 2-part report addresses your concerns about lubricating spring-piston airguns. We still have to look at pneumatics and gas guns separately.


Airgun lubrication — spring guns: Part 1

by Tom Gaylord, a.k.a. B.B. Pelletier

Today, I’m starting a long series on lubricating airguns. Blog reader Joe asked for this; but as I was researching the subject, I stumbled across another request that came in through the customer reviews on the Pyramyd Air website:

“I wish that RWS or Pyramydair would explain the process and frequency of oiling these RWS rifles in particular the RWS mod 48. Everyone I talk with says the RWS owners manual is outdated and that with the new seals they use does not need to be lubed maybe for years….I purchase the RWS chamber and cylinder oil at a cost of almost $30.00 and now am told I probably will never need it? This topic should be cleared up once and for all by the manufacturer.”

Perhaps this customer is referring to RWS Chamber Lube and RWS Spring Cylinder Oil as the two products he purchased. And they do add up to $28 before shipping. Are they necessary? Should he have bought them? That’s the question I’ll start answering today.

This subject is so vast and complex that I cannot address it in a single report. In today’s report, I’m only going to look at lubricating the piston seal. That constitutes about half of the lubrication requirements for many airguns, in my opinion. In the next installment, I’ll address all other spring gun lubrication, including the mainspring and piston.

Leather piston seals
In a spring gun, the piston seal is what compresses the air when the gun fires. As the piston goes forward, the seal keeps the air in front of the piston, where it gets compressed because the only escape is blocked by the pellet sitting in the breech. If the gun’s working properly, all other avenues for the compressed air to escape have been blocked.

In the past, pistons were sealed with a leather pad or cup. Leather is an ideal material for this job. It’s rugged, lasts a long time and will conform to the shape of the compression chamber after a few shots — much like a leather shoe that eventually fits your foot perfectly.

leather piston seal
This cup-shaped leather piston seal is for a Chinese spring rifle.

To do its job, a leather seal has to stay soft and pliable, and oil is the best thing for this. As the spring gun operates, a little of the oil is consumed with each shot, so a leather seal needs to be oiled frequently to stay soft. How frequently? In some older guns, I’ve found that oiling every few weeks is necessary if they’re shot a lot. Certainly, all guns with leather seals need a couple drops of oil at least once each month if they’re to be shot. You can leave a gun with leather seals unoiled for years if you don’t shoot it; but before you start shooting it again, that seal needs to be oiled. When I start shooting an older gun that I know has leather seals (I use references for finding out things like this), I put about 10 drops of oil through the air transfer port and let it soak into the seal for at least an hour, although a half day is even better.

What oil to use?
The type of oil you use depends on the velocity of the gun. Guns that shoot less than 600 f.p.s. in both .177 and .22 caliber will be oiled with regular household oil. Any petroleum-based lubrication oil will do. Yes, gun oil will also work. For guns that shoot faster than 600 f.p.s., I use silicone chamber oil, like the product listed above. The spring cylinder oil is not for chambers and should not be used on the piston seals of these guns.

Synthetic seals
Starting in the 1950s, manufacturers began experimenting with piston seals made from synthetics. Some of them, like the ones used by Anschütz and Falke, worked well and lasted for many decades. But others, such as the seals used by Walther on all their airguns and the seals that Feinwerkbau used on the 121 and 124/127 sporting rifles, were made from a material that dry-rotted within about 20 years. If they were oiled by anything, they failed even faster. These seals started out as a light beige color, but as they absorbed oxygen and oil, it turned them dark yellow and brown until they began to break apart in waxy chunks.

Diana was one of the last companies to switch from leather to synthetic, and they had the benefit of watching the others. They were still using leather seals in their powerful model 45 rifle in the late 1970s, at a time when that airgun had broken the 800 f.p.s. “barrier.” When they started making synthetic piston seals, they used a blue-colored material that was tough and long-lasting. It’s interesting to note that the others adopted similar piston seal material when they finally realized their seals were perishing in use.

Diana piston seal
The blue Diana parachute seal is so rugged that hobbyists use it for many other airguns. It needs very little oil!

modern FWB piston seals
These 2 FWB 124 seals are made from modern synthetic material, yet they look like the original ones. The one on the right has been inside a rifle for a few thousand shots. It looks bad but is still in great shape and will last for many decades.

Don’t fixate on the color blue for piston seals! These synthetics can be colored any way and still be fine. I have modern FWB 124 seals that look similar to the old seals in color, yet they’ll last indefinitely. It’s the material, not the color.

Which oil to use?
With synthetic seals, I always use silicone chamber oil. That’s SILICONE CHAMBER OIL — not brake fluid, silicone spray lubricant or any other concoction. Chamber oil is for piston seals. It does not lubricate metal parts because the viscosity is too low. It’ll ruin metal parts if you use it that way. On the other hand, nobody knows what will happen to a gun that’s lubed with anything other than SILICONE CHAMBER OIL.

Diana recommends using two drops of chamber oil on the piston seal every 1,000 shots, and one drop on the breech seal at the same time. That’s it. To answer the person who asked if he needs the chamber oil, the answer is yes. But one small bottle will last a long time. I’ve observed that most Diana airguns can get by with even less oiling than what’s recommended. One diagnostic for when a gun need its seal oiled is when the seal honks like a goose as the gun is cocked.

Silicone chamber oil has a high flashpoint. Since the air in a spring-piston gun reaches about 2,000˚F with every shot, this is important. This heat is adiabatic — it doesn’t heat the gun because the interval is too brief.

Overlubing vs. underlubing
It’s almost impossible to overlube a leather piston seal. And it does not harm the seal if you do.

On the other hand, overlubing a synthetic seal can start the gun detonating. Not dieseling — most spring guns diesel. When you smell burning oil, your gun’s dieseling. Dieseling is just a few oil droplets vaporizing with each shot. It’s perfectly normal in a spring gun.

Detonation is when a lot of droplets vaporize and cause an explosion. That will damage your piston seal if it’s allowed to continue for a long time. It can also break your mainspring.

So, dieseling is okay, but detonations are bad. And overoiling synthetic seals causes detonations.

Do you see why I had to cover just the piston seals today?


Diana model 60 recoilless target rifle and HW 55CM: Part 2

by B.B. Pelletier

Announcement: Brendon Krahn is this week’s winner of Pyramyd Air’s Big Shot of the Week on their facebook page. He’ll receive a $50 Pyramyd Air gift card.


Brendon Krahn is this week’s Big Shot of the Week. He’s sniping at starlings with his .177 Remington NPSS.

Photos and test results for the Diana 60 by Earl “Mac” McDonald

Part 1


The Diana model 60, which is a Hy-Score model 810 in this case, is a breakbarrel target rifle from the 1960s and ’70s.

That’s right, sports fans, today you’re getting a twofer. For the benefit of our readers outside the U.S., a twofer is slang that means “two for the price of one.” I decided to report on both Mac’s Diana 60 velocity test and my HW 55 Custom Match velocity test for reasons I will explain in each part. Grab a large cup of coffee and an extra Danish and sit back!

The Diana model 60 target rifle

We’ll look at Mac’s rifle first. Today, I’ll reveal the one thing that’s been troubling Mac about his rifle, so it doesn’t take a detective to know that it has to do with velocity.

The cocking effort of his breakbarrel rifle is 28 lbs., which seems high to me. Mac says it doesn’t feel that high because, for some reason, it gets lighter toward the end of the cocking stroke. He also cautions us to beware of the rack-and-pinion noises that these guns have when they’re cocked. To all that I have to say this.

There shouldn’t be any noises when this rifle is cocked. I’ve owned several Giss-system rifles and pistols and shot a lot more, and none of them made any extra noise when they were cocked. That’s clue No. 1. And, I’ll explain how the Giss system works next.

Clue No. 2 is the lighter cocking effort toward the end of the stroke. That’s atypical for a breakbarrel, but Diana has the reputation for breaking mainsprings. When they do, they get smoother. They don’t make any noise, nor do they bind during the cocking stroke. I’ve certainly seen a half-dozen Diana rifles with broken mainsprings and they all acted this way.

How the Giss contra-recoil system works
The Giss contra-recoil system consists of two pistons connected to each other. The real one goes forward when the gun is fired, and a dummy travels to the rear at the same time. The real piston is the only one that has a piston seal, and it’s the one that compresses all the air for the shot. The dummy piston has no seal and is just there to provide an equal and opposite reaction to the real piston. When the real piston slams to a stop, the dummy piston does too at the same instant. The EFFECT of this is that the impulse of each piston cancels the other. The first time an airgunner experiences it he’s usually blown away because, when the gun is timed right, absolutely no firing pulse can be felt.

Of course, timing is the principal concern in a gun that uses the Giss system. That’s why I never recommend a person try to repair his own gun. Sometimes, a mechanical genius like Nick Carter who writes Another Airgun Blog will be able to dive right inside a Giss gun and find no obstacle he cannot understand and overcome, but the average person will just create a basket case.


Looking straight down on the top of the model 60 action, we can see the two telltale caps that cover the gears connecting the two pistons to each other. All Giss-system guns have these caps.


This simple graphic shows how the two pistons oppose each other.

Velocity test
I’ll tell you right now that Mac experienced lower velocity than he expected from this rifle. An Air Rifle Headquarters catalog (the original company) from 1973 gives the velocity of the model 60 as 546 f.p.s., without specifying what pellet was used. That would probably translate to about 550-570 f.p.s. with the pistol-weight target pellets we use today. Mac wasn’t getting that.

He asked me what I thought about putting a drop of silicone chamber oil through the air transfer port to lubricate the piston. We know that these older target spring guns came with seals that dry-rotted over the years, and chamber oil will speed up their demise, but I figured he had to find out somehow, so he did it. But it didn’t cause the seal to destroy itself. It simply boosted the velocity about 12 f.p.s. with no change in how tight the velocity spread was.

The first pellet he tried was the H&N Finale Match Rifle pellet that weighs 8.18 grains. They averaged 457 f.p.s., with a 22 foot-second spread from 445 to 467 f.p.s. The average muzzle energy was 3.79 foot-pounds.

Next, he went with a domed pellet. JSB Exact Diabolos are domed pellets that would not normally be fired in a target rifle unless the target was something other than paper. But Mac also uses his target rifles for mini sniping, so he tested this 8.4-grain pellet anyway. It averaged 474 f.p.s., with a 16 foot-second spread from 465 to 481 f.p.s. The average muzzle energy was 4.19 foot-pounds.

The final pellet Mac tried was the old standard RWS Meisterkugeln pistol-weight wadcutter. Today, they only weigh 7 grains, but Mac had some older ones that weighed 7.7 grains. They were a very loose fit in the breech and averaged 458 f.p.s., with a whopping 37 f.p.s spread from 442 to 479 f.p.s. The average energy generated was 3.59 foot-pounds.

Conclusions
Both Mac and I think the rifle isn’t performing up to spec. Mac found some stated velocity figures of 460 f.p.s. in print somewhere, but he thinks it’s a transposition of 640 f.p.s., which is where a few of the 1960s and ’70s-era target rifles were.

I now believe the rifle has a broken mainspring. Mac thinks it’s just a tired one. Either way, the thought that his gun isn’t performing up to snuff is getting under his skin, so I advised him to have it repaired by either Pyramyd Air or Umarex USA so he’ll know for sure.

Nevertheless, the rifle still shoots as it should and there will be a part 3 coming soon. Let’s go to Part 2 of the other target rifle on today’s menu.

The HW 55 CM target rifle

Part 1


Is this Custom Match the best HW 55 ever made? Read the report to find out.

I’m putting this additional report here for a couple reasons. First, I didn’t want to go too long without reporting on it. More importantly, I thought I might have to do an extra report on this rifle. As luck would have it, that’s how it turned out. While this is Part 2 and a velocity test, the next part will also be about velocity.

Remember that the HW 55 CM was the rifle that I felt had a harsh firing cycle back in Part 1. After I tightened the stock screws, some of the harshness went away. Even after that, the rifle was still feeling harsher than I felt it should for what it is.

Several of you readers thought that when the gun went back to Beeman for a rebuild, they probably installed the upgraded HW 50 sporter mainspring that would have boosted the power. The only way to find that out is with a chronograph, so that’s what I did. According to Air Rifle Headquarters catalog data, once again, a regular HW 55 should shoot H&N pellets at 650 f.p.s. Unfortunately, they don’t give a lot more data about the specific pellets they used for the test.

The rifle does still shoot a little harsh. When you’re peering through a peep sight, the smallest recoil becomes instantly noticeable. In this rifle, it’s unpleasant. The peep comes straight back and bumps into my skull when I fire. My Ballard rifle does the same thing, only its peep is on a tang sight that collapses forward when it contacts my eye. The HW 55 sight, in contrast, remains rigid and allows me to absorb all the impulse of each shot. Well, I’ll be danged if I’m going to put up with that!

The plan is to quiet the shot cycle with black tar, if possible. If the gun has extra velocity it doesn’t need, I’ll be only too happy to do that.

The cocking effort is just 20 lbs. on the nose, and the ARH catalog says to expect a weight of just 15 lbs. There’s another small deviation from what would be expected. Even the HW 50 mainspring isn’t that powerful, and the long almost-18.5-inch barrel may be providing the extra leverage to reduce the force.

The first pellet I tested was the RWS Hobby, that standard candle of high-velocity lead pellets. At just 7 grains, it’s not only light, but often it turns in surprisingly good results downrange. Hobbys averaged 694 f.p.s., with a 17 foot-second spread that went from 684 to 701 f.p.s. The muzzle energy is 7.49 foot-pounds. I would love to say that this speed wasn’t expected, but it wasn’t far enough out of line to be definitive.

Next, I tried H&N Finale Match Pistol pellets. They weigh 7.56 grains. They averaged 632 f.p.s., with a 14 foot-second spread from 625 to 639 f.p.s. The average muzzle energy was 6.71 foot-pounds. That seems right on the money for a stock mainspring.

The final pellet I tried was the RWS R-10 Match Pistol pellet. Although they’re just as light as the Hobbys, they go the same speed as the heavier H&N Match Pistol pellets. That would indicate a bore-fit issue.They averaged 632 f.p.s., with an 18 foot-second spread from 619 to 637 f.p.s. The average muzzle energy was 6.21 foot-pounds.

Evaluation
I can’t tell for certain that the mainspring has been upgraded, but I do know that the rifle has way more velocity than I need. The next step is to lube the spring with black tar to see what EFFECT, if any, that has on the shot cycle. While Mac wants more velocity, I’m looking to get rid of some for the sake of smoothness.

I’ll break these two reports into separate reports for their respective accuracy tests. But before I do the accuracy test with the HW 55 CM, I’ll lube the spring and retest the velocity results, giving this rifle one extra report.