Making a Spring Compressor

spring compressor

Before you can do serious tuning or repair work on a spring airgun, the first tool you need is a spring compressor. You can’t buy one- but you can make one very easily. I’ve seen many plans in airgun magazines over the years, and they’re all pretty similar, as they all do the same job: Hold a barreled action steady while releasing or compressing the mainspring. Where they differ is in the details that each gunsmith adds to their version.

screw clamp

Mine is massively overbuilt- the base is heavy enough and large enough to be self supporting, and one of these days I’m going to build legs for it. Until then it just gets dropped on whatever workbench is handy when I need it. As you can see, the bulk of it consists of a pipe clamp attached to a wooden base. At the free end, the pipe is screw to a flange that in turn is screwed to a vertical surface. The other end sits on a spacer, with a screw passing through the pipe and the spacer into the base. Along the pipe are a series of adjustible clamps that hold the gun steady as the spring is released or compressed.receiver clamp

At the fixed end of the pipe clamp there’s a sliding, locking piece that serves as a fixed point in clamping. At the other end is a screw clamp that attached to the free end of the pipe. Adjacent to both is a piece of wood that is bored to slide along the pipe and act as padding between the metal jaws of the clamp and the gun. Some airgunsmiths like to add extra padding in the way of cork or felt to these pads, but if you make your clamp of of softwood, as I did, there’s no need.

To release a spring, the gun is first disassembled and clamped in the fixture with the clamp run in as far as it will go- this provides enough room to extend the spring after it is released. Then, any screws or retaining pins holding the end block in are removed, and the clamp is backed out, releasing the spring tension. If the screw clamp doesn’t go far enough, release the other end of the pipe clamp and back that off- it’ll be under very low tension at this point.

To replace a spring, assemble the parts, back the clamp out as far as it will go, and then manually slide the far end of the clamp as far forward as you can. Use the screw clamp to finish compressing the spring, replace the retaining pins and screws, and there you are.

Cleaning Airguns

Even though they don’t leave as much residue as do firearms when fired, it’s still a good idea to periodically clean the barrel of your spring or pneumatic gun. If you’re a competitor, this goes without saying, but even plinkers and hunters can benefit from the increased accuracy that regular cleaning delivers.

When I was a competitive shooter, cleaning was generally a ritual perfomed the night before a match; these days it’s something I do when it occurs to me that I haven’t done it in a while Sometimes, with a gun that doesn’t get shot very often, that’s once a year or less. That’s okay. Unlike, say, black powder guns, where the barrel will rust away if not cleaned immediately after shooting, a neglected airgun barrel won’t decay in any way without cleaning.

So what do you need to clean your barrel? Two things: A good cleaning rod, with tips, and a cleaning product of some sort. I keep a Beeman pull-through rod in my shooting kit, where it’s available for use in the field. At home, I like a stainless steel rod, as it doesn’t less damage to a barrel than the more common aluminum rods. You’d think that aluminum, being softer than steel, would be safer, but there’s a catch: Alumnum, when exposed to air, immediately forms a protective oxide layer, and this oxide is very hard- aluminum oxide is used to make sandpaper and grinding wheels- and can actually scratch the barrel. A highly polished stainless steel rod won’t leave any marks

For a cleaning compound, do NOT use an agressive firearms cleaning solvent like Hoppes #9. It’s far more agressive than you need, and it can attack o-rings and other seals. And should it get into the compression chamber, you may find yourself buying a new spring and piston seal. I’ve been using “Break Free CLP” for many years on airguns and firearms, and I think it does a very good job. There are a good many similar products on the market, so feel free to experiment.

To clean your gun, push a few patches wetted with the CLP through the barrel- breech to muzzle, if you can- untill the patches come out clean. Then push dry patches through until they come out dry, with no sign of cleaner. There’s no need for scrubbing with bronze brushes unless you have actual leading in the barrel.

What about those cute felt pellets that you’re supposed to shoot down the barrel to clean it? Throw them away. They don’t ofer enough resistance when shot in a spring gun to prevent damage to the spring and piston seal. I suppose you might use them in a low-powered CO2 or Pneumatic gun, if you really wanted to, but a rod and patch will do a better job.

The last step is to fire your airgun a dozen times to clear out any cleaning residue and “dirty” the barrel, as target shooters say. With every shot, a little residue gets deposted in the barrel and some is scrubbed out. Equilibrium is generally reached in a dozen shots, and after that the condition of the barrel stabilizes and accuracy is maximized.

airgun muzzle brakes (and silencers)

In my last post, I noted that one way of building a muzzle brake is to create a chamber in which gasses escaping the muzzle would expand and then be released more slowly. Attentive readers may have noticed that this is also a workable definition of a silencer. The typical airgun muzzle brake would not make a very good silencer- but that’s not always good enough for the BATF. It was, however, enough for Beeman to modify the silencer mounted on the Theoben Eliminators that they sell as Beeman Crow Magnums.

(It may surprise readers to learn that airgun and firearms silencers are less regulated in Europe than in the US; even in countries with very strict firearms laws, silencers are looked upon as a “good neighbor” device one uses to be considerate of those living nearby. On a visit to England some years ago I was surprised to see the wide variety of silencers available in a gun shop I visited.)

There’s a fairly hysterical article on airgun silencers posted at the Beeman site which does contain some good- but out of date- information. What it says is that a silencer is whatever the BATF decides it is, which is true. The BATF determines whether a device is a silencer by taking a device, attaching it to the end of a .22 rifle, and seeing if it attenuates the sound in any way. As many have noted, there are a lot of relatively innocuous things out there that would fit this definition, including lawn mower mufflers, plastic pop bottles, and a good many vegetables, and indeed, the BATF once prosecuted a felon who was arrested during the commission of a crime with a potato stuck on the end of his pistol.

It has been accepted wisdom for some time in the airgunning community that a silencer built into an airgun is not a prohibited device under the National Firearms Act or the Gun Control Act of 1968, since airguns are not firearms according to the BATF- but the Beeman article argues otherwise. The BATF, the Beeman site tells us, has been known to saw a silencer off a paintball gun, tape it to a .22, and do their test. And as the article notes, you may be right in the end, but defending yourself from prosecution may cost you several tens of thousands of dollars as well as your job and a good chunk of your life. But the Beeman article is well over a year out of date- and manages to misquote and misintepret a BATF ruling as well.

In ATF 2005-4, the BATF clarified matters for the airgun and paintball community. In the prologue to the ruling, it states that Certain devices intended to diminish the report of paintball guns are not “firearm silencers” or “firearm mufflers under the Gun Control Act of 1968. The ruling goes on to describe how the BATF sawed a dedicated silencer, mounted it on a .22 and acheived a sound reduction of 7.98 dB, which is is to say not very much.

But it also goes on to say that it is the removal of the silencer from the paintball gun that constitutes the “making” of a silencer- which is prohibited under the GCA. It further concludes:

Held, a device for an unregulated paintball gun, having a permanantly affixed, integral ported ballel and other componants, that functions to reduce the report of the paintball gun is not a “firearm silencer” or “firearm muffler” as defined, as the device is not one for diminishing the report of a portable firearm.

Held, removal of the permanantly affixed ported barrel and other componants from a paintball gun is a “making” of a silencer under the GCA and NFA that requires advance approval from ATF.

This should cover airguns with built in muzzle brakes and silencers/moderators as well, as airguns are also unregulated devices insofar as the BATF is concerned- but I’m not a lawyer, so use your own judgment. Making a silencer, or a muzle brake that could be construed as a silencer, and then attaching it to an airgun, or obtaining an airgun silencer from England would still still be a violation of the GCA and NFA, so do keep that in mind. If you want to go that route, fill out the necessary BATF forms, and pay the $200.

And there is always the chance that the BATF may decide one day to regulate high-powered airguns, in which case we’ll have to revisit this issue.

muzzle brakes

There are a lot of devices out there marketed as “muzzle brakes” (and sometimes, “muzzle breaks”) for airguns. Most of them are worthless as anything more than decoration. To understand why, let’s look at a real muzzle brake.

C1 muzzle brake

This is a custom muzzle brake made for a Beeman C1 carbine by a gunsmith who specializes in firearms muzzle brakes. It was made as an experiment, to see if it would be of any help on an airgun.

Basically, it’s a barrel extension, bored out slightly larger than the bore of the rifle, with a number of holes drilled at right angles to the bore. In a firearm, these holes would serve to bleed off propellant gasses before they exited the end of the barrel. In modern firearms, over half the recoil energy can be due to escaping, gas, so you can see why such devices are commonly fitted to magnum rifles- as well as lightweight artiliary pieces and main tank guns. Sometimes the brake is designed to vent gasses backwards, further reducing recoil. If you can get rid of recoil energy, you can make a gun lighter, and still controllable.

You can also make a muzzle brake by providing a chamber into which propellant gasses can expand at the muzzle, capped off with a constriction at the end that is just large enough to allow the bullet or pellet to pass through- but which will slow down the escape of the expanded gasses.

Some guns- like pistols designed for rapid fire competition- have muzzle brakes that vent escaping gasses upward, to counter muzzle climb and help the shooter stay on target.
Of course, the recoil from the air escaping an airgun is practically negligible- but there’s a secondary benefit to muzzle brakes. The “bang” you hear when firing a gun is the gas expanding supersonically from the muzzle. This gas leave the barrel at a much higher speed than the bullet- it’s much lighter- and actually passes the bullet in the form of an expanding shock wave front. This can have a negative effect on bullet stability, especially with lightweight projectiles. If you can reduce the amount of gas hitting the pellet after it leaves the barrel, you should be able to increase accuracy.

In the case of the brake made for the C1, there was a small, but repeatable, increase in accuracy. I’m not sure if it makes sense to do a $200 custom muzzle brake on a gun that at the time sold for less than that, but it did establish the utility of the idea. But are there cheaper muzzle brakes that work as well?Beeman Muzzle Brake

The cheapest device on the market sold as a “muzzle brake” is the Beeman, a piece of lathe turned and anodized aluminum advertised as being “precision-turned from the finest aircraft-grade aluminum” that sells for $29. If we look at a cross section, we see that escaping air isn’t vented or directed away from the axis of the bore, although there is a widening and then a slight contraction at the end. This does create a small expansion chamber that might delay the expanding shock wave- although not by much. Beeman doesn’t make any great claims for the device other than in protecting the end of the barrel, adding a bit of steading mass, and making a nice cocking handle. It’s cheap, and indeed performs all these functions just fine. I’ve installed a few on guns I’ve owned.

For $50, Beeman will sell you their “Crow Magnum” muzzle brake- actually a modified Theoben unit. This consists of an attractive polished cylinder with a large expansion chamber. Again, it’s mostly a muzzle weight and decoration, as it’s missing the end baffle- the part that delays the shock wave and slows the expanding gasses. Removing the baffle turns an erffective muzzle brake into a barrel weight. Exactly why Beeman did it this way will be the subject of a future essay.