21/28 Run Problem

[maravillamike]

Any suggestions on how to solve Thompson 21/28 firing problem. Will fire 2 or 3 rounds then fail to fire. Primer is barely dented on the round. May then fire several rounds 6-8 before it happens again. Have replaced firing pin & spring to no avail. Also any one know of a source for an original fore grip for the 1921/28 overstamp Colt ? Thanks

[gijive]

maravillamike,

 

Are you using box magazines or a drum magazine? Maybe the feed lips are out of spec and are causing the forward movement of the bolt to lose inertia, thereby not feeding the round properly. In addition to replacing the firing pin and firing pin spring, you should also try a new recoil spring. These are sometimes the reasons for light primer hits.

 

Also make sure the oiler pads and bolt and blish lock are sufficiently lubricated.

[Bob]

Hows the buffer pilot and alignment? check the recoil spring for binding.

I saw one that the oiler was bent and causing the pilot to cock to one side and bind the spring in the actuator. Good luck.

[Balder]

Mike,

 

Your recoil spring could be too weak, try replacing it.

 

Balder

[PK.]

All good suggestions. Is your barrel original or replacement? If replacement, who was the maker?

[Ron A]

PK has a good point - when I changed a Bbl to a Kahr Bbl (why would anyone want a Kahr Bbl?) I had the same problem. The chamber is not correct, they were cut to a standard 45acp chamber and the edge was not beveled. The slowing down of the round into the chamber caused light primer hits. My guess is that he is on point - spring replacement is a good idea anyway.

[maravillamike]

Thanks for all the suggestions. I am using several box magazines & 1 drum with the same problem occuring. The barrel is original to the gun. I will check out the recoil spring, lubrication, buffer & oiler. Thanks again Mike

[JimFromFL]

Are these reloads or factory ammo being used?

Inspect each round closely for any indentations.

[Mike Hammer]

This sounds like the same problem that I had with my WH '28. The first thing to try would be using a new mag so that you can eliminate the mag feed lip question, this is the easist fix. Then try a new spring. Also check your length on the firing pin, could be too short. Put upward pressure on the magazine when you fire, this could show that your magazine is not fitting high enough into the mag well, you may need a new mag catch. Feed ramp may need polishing. Try this easy stuff first, then send it to a pro if you have to like Stan Andrewski or PK here on the boards.

 

Mike Hammer http://www.machinegunbooks.com/forums/invboard1_1_2/upload/html/emoticons/wink.gif

[JimFromFL]

Along the lines of what Phil stated... If it is truely a Colt and original barrel then it should not require any major modifications.

 

There are a lot of good suggestions.

1 - check the ammo.

2 - push up on the mag. Even try to find someone locally who will let you borrow a mag they know works 100%.

3 - inspect each round for indentations

4 - Use a caliper to measure the lenght of the firing pin.

5 - Replace the internals BEFORE taking any power tools to the item. Worse case scenario is that you end up with spare parts that only get more expensive each year. I have replace a "new" part only to have the same problem, but replace it with a 2nd "new" part and have it work. Keep in mind there really are not too many "new" parts left.

6 - Listen and even video tape it. When you fire enough rounds you get good enough to tell when a round was going to jam by how it sounded as it cycled.

 

The ultimate thing would be to find someone close to swap out parts.

 

Good luck and keep us up to date on the progress.

 

[giantpanda4]

Jim from Fl has an excellent point in his reply:

 

Replace those expensive internals with a 2nd set before carving anything!

 

Or - if you get really tired of that thing - sell it to me! http://www.machinegunbooks.com/forums/invboard1_1_2/upload/html/emoticons/biggrin.gif

 

Enjoy it!