by Tom Gaylord
Writing as B.B. Pelletier

mainspring compressor
Mainspring compressor.

This report covers:

  • Can you make a mainspring compressor?
  • BSA Meteor
  • Description
  • Bridge
  • Headstock
  • Tailstock
  • Legs
  • General

Today I’m going to show you a mainspring compressor that I will use in tomorrow’s blog. I was asked this week by a new reader to show the tools needed to safely disassemble a spring-piston airgun. Here is the request.

Great web sight!  As a “newbee” to air rifles, I find it a wealth of info!  Having a hard time trying to start a new post in the blog forum..  Specifically, I’m looking to find out if anyone makes proper tools for the correct disassembly of the Benjamin Trail NP XL 1500.. Looking for a proper end cap removal tool, and a spring compressor.  I was an armorer for years in LE, with an incredible amount of proper tools for “firearms”.  Just want to make sure that maybe there’s a place to purchase proper tools for air rifles out there.


I didn’t answer him that gas springs, which the Crosman/Benjamin Nitrop Piston is, usually do not require mainspring compressors, because I knew this blog was forthcoming. I wanted to work it in, so I told him I would answer him in a blog later in the week.

The truth is, gas springs — and, yes, that is the correct generic name for all of them, be they Nitro Pistons, gas rams, gas struts or anything else — are usually under no preload when they are in the rifle. If there is any preload (spring under pressure when it is in the gun) the travel is no more than 1/2 inch or so. So usually you can just drift out the pin or remove the bolt that holds the end cap in the spring tube and the gas spring drops out as a unit. Don’t disassemble a gun unless you know for certain how it comes apart, but this is what you will usually find.

We are here today to learn about a mainspring compressor that can be used to disassemble almost any spring-piston airgun that has a conventional coiled steel mainspring. I have been using a compressor like this one for over a decade and in fact I helped with its development. This compressor was invented by B-Square, under the direction of the company owner, Dan Bechtel. I consulted with him during its development and the result was a tool that hundreds of airgunners now own. But to be honest, mainspring compressors are not very exciting, so airgunners tend not to buy them. They tell themselves that can make one if need be, and then I hear all the whining and crying when the day finally dawns that they really do need one.

Can you make a mainspring compressor?

Yes, you can make a mainspring compressor. In fact building a mainspring compressor is so easy that hundreds of them have been made by shooters over the years. Some guys have even made them for resale, but every one of those guys stopped when they discovered how poorly mainspring compressors sell. A mainspring compressor is like a good pair of pliers. When you need a pair almost nothing else will suffice, but when you don’t need them you never even think of them. No, I will go even farther. To a person about to disassemble a spring gun a mainspring compressor is like a bench vise. It is absolutely essential.

Don’t get me wrong — airguns can be disassembled without using a compressor. Some guns, like the Air Arms TX200 Mark III, are so easy to disassemble that a compressor is never used. But they are the exception. Most spring guns do require a compressor if you want to be safe and have no more than two hands.

BSA Meteor

Tomorrow I’m going to use this new compressor to disassemble my new BSA Meteor Mark I for you. This is so you can see what the innards look like before I start the Tune in a Tube test. That test will be followed by a real tune, so we can compare the results after each tune. If you want to know more about how a BSA Meteor comes apart, read the 9-part report.


This new compressor is sold by Sun Optics. It is fully adjustable and is designed to disassemble the barreled actions of spring rifles and pistols that have been removed from the stock. The parts that contain the action (called the tailstock and the bridge) adjust up and down stainless steel tubes which is what all the holes are for. Sun Optics has even made some improvements over the compressor B-Square made. The B-Square compressor used steel conduit for the legs instead of tubing. The holes in the legs of the Sun Optics compressor are all chamfered for smoother adjustability. I noticed the difference right away.

chamfered holes
The new stainless steel tubes (top) have chamferred adjustment holes. I had to grind the burrs around the holes on the old compressor myself (bottom).


The bridge is the part of the compressor that keepss the spring tube from flexing to one side when the mainspring is no longer trapped. This flexing is the second biggest problem you’ll have when you disassemble spring guns. Controlling the end cap is the only task that’s more important.

The bridge has screws that adjust to center the spring tube in line with both the headstock and the tailstock. That gives you the most working room around the barreled action.

On the old compressor the bolts on the bridge were all left raw. I protect the finish of my guns by wrapping the gun’s spring tube with a heavy leather belt that the screws cannot scratch through. The new compressor has plastic tips on each of these screws.

The tips of all the bridge adjustment bolts have plastic caps. No more leather belt to keep from scratching the spring tube!


One feature of the original compressor that made it the best on the market is the rotating headstock. It allows you to rotate the barreled action from side to side while still maintaining pressure on the end cap and therefore on the mainspring. This allows the positioning of the tube so pins can be aligned and/or drifted out. This is the key to the compressor, because many spring gun actions are held together by pins. The new compressor headstock rotates in the same way as the old one.

The new compressor headstock also has a hole in the center for a pin to a part the old compressor didn’t have. It’s a pusher block that’s used to disassemble certain spring gun actions, notably BSAs. Unfortunately this block is slightly too wide to fit inside my Meteor spring tube, so I will have to use the plastic pusher block I made when I disassembled my other Meteor. But if I owned this compressor I could easily shave the new block down to fit.

I will also have to enlarge the hole in the headstock, because the pin in the pusher block is too large to fit. It does fit the hole in the tailstock, but I don’t know anyone who would use it that way.

The headstock turns to allow access to different parts of the gun’s spring tube. This new headstock has a hole (arrow) for the pin of a new pusher block.

headstock with block
New aluminum pusher block comes with the new compressor. The pin at its base is too large to fit the hole in the headstock, so some drilling will be needed.


The tailstock is where the muzzle of the action rests. It adjusts along the two steel rods to fit the gun you are working on and give the headstock screw lots of room to travel. It also has a hole for the pusher block, though I cannot think of a reason to use it that way.

The new tailstock also lacks the raised bump the old tailstock had. That was inserted into the muzzle of the barrel, to keep it from walking when the action was under pressure.

The tailstock adjusts for the length of the gun. Hole is for the pusher block pin, but I don’t know how it would be used on the tailstock. Gone is the raised bump the old compressor had to keep the barrel from walking.


The new compressor can work like the old one, or you have the option of installing 4 longer bolts that also serve as legs. Two fit the headstock and two fit the tailstock. The compressor then stands up away from the work table. This gives even more access to the spring tube.

The longer bolts that serve as legs have been installed. See how they elevate the entire compressor?


The compressor comes with no instructions. Like a bench vise, you should know how to use it if you own it. That doesn’t mean you automatically have to know how to disassemble every spring gun mechanism. I doubt if anyone knows that. But spring guns belong to different groups that have similar features. With experience the worker learns what to do with any action to take it apart. The compressor is just a tool for a specific set of tasks within that body of work.

Is it “worth” it? This compressor retails for about $200. Is it worth the price? Pyramyd Air does not carry the compressor at this time, so you will have to go directly to Sun Optics. Pyramyd Air probably remembers how people complained about paying half the price of this one for the old compressor.

The thing is, if you work on a lot of spring guns a compressor of some sort is good to have. This is the best one I have seen, and I have seen dozens of different ones, besides designing and building one of my own that I documented in the R1 book.

For a few workers this compressor is worth the price. And you had better get one now, because who knows how long they will be available?

Tomorrow I’ll disassemble the BSA Meteor Mark I using this compressor. If anything stands out as I do that I will be sure to include it in the report for you.