Thompson Contender Barrel Problem

[seaboltm]

I have several contender barrels. I have one in 45/410 that I can't get to fire. The hammer will not fall all the way as the hammer block safety catches it.

I switched out the locking lugs (two piece) and spring from a 223 barrel that functions fine. The 45/410 barrel still won't allow the hammer to drop all the way!

I have no idea what to look for next. Any ideas?

[JLarsson]

Sometimes, the collective tolerances add up in the wrong direction. If your 45/410 barrel cannot physically close all the way because it is slightly to long from the pivot pin hole to the chamber end of the barrel, it will have to be faced off a bit until it can close. Changing to the two-piece locking lugs was a good start, though.

Close the barrel on a .001" feeler gauge, making sure the feeler gauge is situated between the bottom of chamber and the breech face. Gently try to pull it out. If you cannot, then you probably will have to have the barrel faced off. Anybody with a lathe could do this and you shouldn't have to take much off.

If the .001" feeler gauge is not trapped between the barrel and the breech face, then you will have to stone the tops of the locking lugs until you get them to seat fully. Check for this by marking the tops of the lugs with sharpie and open and close a few times. Look at how much of the ink is scraped off. Do the same thing with a barrel that locks up fully and fires. Compare the two so you get an idea of what kind of engagement is required. Then stone the tops of the lugs, being extra careful to maintain all angles precisely.

Which generation frame is this? G1 or G2? If G1, which version? Rimfire/Centerfire selector as a screw on the nose of the hammer? Crossblock selector? Switch selector on top of the hammer?

[seaboltm]

It is G1, selector is a screw on the nose of the hammer. The barrel will close fine. It simply won't allow the hammer to go all the way forward.

[JLarsson]

If the rear of the barrel is tight against the breech face of the frame, that can keep the locking lugs from engaging fully. If this is the case, stoning the lugs won't change anything. You need enough clearance at the back of the barrel so the barrel can seat fully. It doesn't take much one way or the other to make a big difference.

Are you saying you put a feeler gauge in there and you're sure you have clearance between the barrel at the bottom of the chamber and the breech face?

One other obscure possibility is that the extractor is too long and is causing the barrel not to seat fully. It's probably the locking bolts (lugs), but these other things CAN happen.

[seaboltm]

Thanks to JLarsson! He PM'd me this picture, and with 5 light passes with a fine cut swiss file (5 seconds of work) the barrel fires fine!

[JLarsson]

To be fair, I should say that I "stole"that picture from a different thread here on Cast Boolits, and just added the red marks indicating the areas to be stoned.

The main thing is, it works!

[seaboltm]

Hell yeah it works! All Hail JLarsson! I have been F**!!! with this barrel for weeks! 5 seconds!

[David2011]

To be fair, I should say that I "stole"that picture from a different thread here on Cast Boolits, and just added the red marks indicating the areas to be stoned.

The main thing is, it works!

V.cool! Welcome to Cast Boolits.

David

[JLarsson]

Thanks, David. This is a nice place.

[cbrick]

JLarsson is 100% correct. I've owned more TC barrels than I can remember and while it's true they are interchangeable barrels (kinda) they are each individuals as are the frames and quite often barrels need proper fitting to the frame they will be used on. When shooting silhouette I would fit certain barrels to a particular frame and never use those barrels on another frame. Pretty rare the barrel needs to be honed but that does happen also, most often proper fitting of the bolts does it. With extended use the bolt table on the frame can become worn and that requires frame replacement. Don't know about today's T/C but they used to be very good about replacement frames due to worn bolt tables.

Rick

[JLarsson]

I don't know what they do with the frames, especially now that the original frames have been superseded by the G2 frame and S&W has acquired T/C. Something I meant to ask Seaboltm is if his early variation frame had been converted to "easy open". The first frames, with the rf/cf selector as a round rotating piece on the face of the hammer had the trigger guard pivot point at the front of the frame, toward the muzzle. Thompson Center used to convert these by drilling a hole for a pivot pin more toward the middle of the frame, front to back. The non easy-open frames could be difficult to get open sometimes.

I had a .41 Mag barrel that would open itself after every shot. I called it my "auto-eject" barrel. I sent it in to TC and they fixed it for me.

[cbrick]

Check that 41 for proper bolt fit with a magic marker as was described. Odds are the bolts aren't seating fully. Also possible is the frame is stretched allowing the bolts to slip.

Rick

[JLarsson]

Yep - we played with it and checked all kinds of things. T/C fixed it right up. What I DON'T remember is whether I sent the frame in at the same time. Might have. I no longer have the barrel, but it was fine when I sold it.

[seaboltm]

I don't know what they do with the frames, especially now that the original frames have been superseded by the G2 frame and S&W has acquired T/C. Something I meant to ask Seaboltm is if his early variation frame had been converted to "easy open". The first frames, with the rf/cf selector as a round rotating piece on the face of the hammer had the trigger guard pivot point at the front of the frame, toward the muzzle. Thompson Center used to convert these by drilling a hole for a pivot pin more toward the middle of the frame, front to back. The non easy-open frames could be difficult to get open sometimes.

I had a .41 Mag barrel that would open itself after every shot. I called it my "auto-eject" barrel. I sent it in to TC and they fixed it for me.

Not converted to easy open. It can be difficult to open at times, but I fairly strong, so no big deal. I thought about converting it, but I spoke with Bellm's company and they said it really wasn't worth it.