Can anyone suggest why, when my TX200 mk III gun is cocked, there is around a .030" movement of the cylinder, fore and aft causing the orings not to seat, except when the piston starts moving forward?

When the gun is uncocked, the spring pressure presses the orings against the barrel end.

I seem to have resolved this gap by putting a .050" steel washer, ground to fit, under the orings. There is an issue of the bolt being that much closer to the piston and that the piston may hit the threaded cylinder head (or bolt).

If the cocking shoe was .030" or .040" longer, this gap would be eliminated. I have tried the stock TX200 shoe and the Maccari shoe. Both are the same.

The barrel nut is tight and the bolt it tight in the cylinder, too.

Can anyone help. This is a curious problem.

Charles

more than likely its incorrect headspacing of the barrell. in other words the barrell should have been set back in the receiver further. this is a mismachining at the factory i think

putting a spacer behind the O rings is really not a cure. they will simply extrude through the gap and have a very short life. I have pretty good lockup on mine and i still replace the top O ring before every match.

if this is a new gun i think this is a warrantee isshe. if not then there is probably a machinist that can re-set the headspace. i would call Tim at
Mac-1 airguns and see what he thinks.

Hi, Larry. Yes, head space. I have a question for you. Should the bolt be torqued down tight into the cylinder? Or should the bolt be backed out to the original witness file marks, about .030", till the shoe puts a little pressure on the orings after the gun is cocked.

Clay could determine the head space. It seems to me, Larry, that I want the bolt to press against the barrel! This would tighten everything up and reduce harmonics. Cept, that that center in the bolt is pressed in. Probably cheaper than trepanning the center tube.

Thanks for writing back. I shoot at Tacoma Rifle and Revolver, in Tacoma Washington.

Dang, facing off the shoulder of the barrel would solve everything.

Every match you change the orings? I finally changed the orings after 6500 shots. If the bolt had a, maybe nylon or something a little bit softer and cone shaped, the cylinder could be adusted to seat onto the female cone shape with a slight press fit.

Anyway, thanks for the info, Larry.

Charles Connolly

The Macarri shoe would have fixed it, if the forward end of the shoe was .050" longer. Then I could shape it to eliminate the head space.

The slop in the compression tube, after the gun is cocked can be fixed in several ways. The best way is to turn down the shoulder of the barrel to receiver contect point. Air Arms, I think, chose to back out the bolt to eliminate the head space, due to their filed witness marks. Macarri says I should replace the compression tube cause it's out of spec.

It appears to me that the slop can be removed by heating and bending the lever, that inserts into the shoe. This won't take much. There is about 0.040" slop. The goal, I think, is to have the bolt just make contact with the barrel and press, a little, with the hand lever, when cocked.

The bolt to barrel contact point is around the 3/8" ID of the bolt. That ID contacts the barrel end causing around .025 gap between the end of the barrel and the bolt. I will lap in this contact point with grinding compound and blue it. This contact point is much like a valve. This will reduce Oring failure.

doing the same thing by putting a bow in the link. i have seen some discussions on the bolt. some have said it is designed to be fully seated. did you ask jm about turning it out?

If you get the lockup too tight you will destroy accuracy because the nipple that holds the seals will hit the end of the barrel, trust me, I've been there already and it kills the accuracy. How big is the hi low spread on a 10 shot string over the chrony? If it's under 20 fps leave it alone. The very first thing the comp. tube does when the gun is fired is move forward and the pressure seals the barrel. The gap can be excessive also, but I've seen guns with lots of play still shoot very accurately. You could also remove the comp. tube and unscrew the plug in the end just a little. It has sealant on the threads and will require a little heat. you will have to epoxy it back in place and if you unscrew it too far the gun may not cock because the back of the comp. tube will hit the end plug that houses the trigger.