I had the epiphany some time ago that air guns, regardless of powersource, are pneumatic systems, tuned to perform at certain levels.

If you change one parameter, it has an effect on the entire system. But I continously forget this, until it bites me.....

I chopped about 8 inches off a chinese underlever, and was truly surprised that it went from smooth shooter to violent recoil in just a few strokes of the hack saw. What turned it viscious was the cutting the barrel, eliminating a lot of the volume the piston was pushing against. Now, without that cushion, the piston is able to move faster, and bottom out violently.

Turns out the that the transfer port on a lot of chinese springers are oversized. After finding this out, I tore it down and found that the TP on this gun is around .156 inches. Optimum, I'm told, is around .115 - .125. I found brass tubing in the same OD as the TP on my gun, and added a very short piece to reduce the ID of the transfer port to (approx. ) .130.

Also added a piece of 1/2" OD brass tubing to the spring guide. The spring _justs_ fits over the brass. This took the twang out, and helped smooth the beast back out.

Result is, between the two tweaks it got to be much smoother without the violent recoil. And quieter too.

The other big thing Ive learned lately is to give finishes time to "cure". My work shop is never... Warm..... so it takes finishes a lot longer to set. Patience is the key here. Or turning up the heat. I think I need to build a hot box for the next refinish project.

Great post Dan. Thanks.

Good tips all. You nailed them. Especially about the entire system needing to be in balance. You cannot just change one thing, without tossing the thing off balance somewhere else. You'd have to assume that you KNEW for sure, that the designer of the system didn't know what he was doing, and that you knew better. I suppose, with quickly made Chinese guns, you might find a way to tighten up the system with closer tolerances. Sounds like you did that. Good job.

I think you are on the right track with the "hot box" idea too. You can heat it with a few simple light bulbs. (The anti-green planet killer type - not the curlieques).

Gary

Thanks for sharing Dan. I learned something there (and not just to not cut the barrel off any of my springers! ).

I've seen one of those hot boxes somewhere with the light bulbs in it... Looked like a good idea to me! The product that came out has been well recieved round these parts!

I really need to start a project. I've got a DS .50 that I never shoot anymore. It has a cracked stock and I would like to shape a finish a replacement but I've not found a stock blank close enough to fitting that makes the project feasible. I've actually got enough tools that I could probably buy a couple bits and spend some time making guides and jigs allowing me to start with just a chunk of laminate or wood but I've not mustered the motivation to do that. Maybe all these project posts will get my motivator fixed! Maybe I'll even mess with the internals if I ever take the gun down...

Jerry Wrote:
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> Thanks for sharing Dan. I learned something there
> (and not just to not cut the barrel off any of my
> springers! ).


Nah Jerry, Whack away! Just think it thru first.... which I didnt do. Twice. I have 2 guns that I whacked, and both reacted the same way. Have only tweaked one, cuz I can pull that one apart without a spring compressor. The other requires some clamps, and 3 other hands to get it all to line back up for reassembly......

(The anti-green planet killer type - not the curlieques).


Ive got a couple of those in the work shop. Take a few minutes to "warm up" then they are ok. Till then, dark and green.....

I first heard about the hotbox concept while working at the famous guitar company that has a plant here in Bozeman. We used it to bring the moisture in finger boards down just before they went to the glue line. It had 4 150 watt flood lamps. Was great to work with during the winter.