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Old 01-16-2005, 11:10 AM   #1
Join Date: Mar 2003
Posts: 39
Thompson 1927A1

I've tried other forums to get info but have yet to receive any on fixing the trigger pull on my Thompson.

I don't know if they all do but my Thompson has the most horrendous trigger pull of any gun I own. Travel is the main problem. The trigger has so much travel before releasing the hammer that most people stop to make sure the safety isn't on. Since I hadn't received any info on improving the trigger I tried a little gun smithing on my own. I'm now waiting for Kahr to send me a new $20.00 firing pin. I took too much material off the bottom of the pin and now it fails to consistantly catch the sear. This causes the gun to fire full auto but with no way of stopping it unless the pin happens to catch the sear again or the mag is emptied.

Other than taking too much off the firing pin I assume that I am on the right track to reducing trigger travel. Is this the correct method or is there another way?

Next time I'll take a few millimeters at a time off.
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Old 01-16-2005, 04:12 PM   #2
Senior Member
Join Date: Jun 2001
Posts: 1,691
The terrible trigger is a direct result of the attempt to build a semi-auto shooting replica of the full-auto Thompson, AND satisfy the ATF.

The trigger can be improved, but this gun is a shooting replica of a historical weapon, NOT a target rifle.
Having a not so good trigger, is simply "the nature of the beast".

DO NOT try for a really short pull. This design is NOT capable of a really great trigger, and trying will result in either ruined parts, failure to cock, or unsafe full-auto bursts

Here's how I used to do it:

Clip about 1 coil off the trigger spring.

Clip about one to two coils off the hammer spring. (The larger diameter spring that fits into the bolt. The hammer is the long cylinder inside the bolt).

"Polish" (SMOOTH, not mirror shiny) the top of the trip. (The lever on the trigger).

Polish the bottom of the sear block where the trip engages it.

LIGHTLY polish the sear block's upper surface, (the top of the sear).
DON'T reduce the height of the sear block. Just polish the area where the firing pin drags over it.

LIGHTLY polish the sear block face that engages the firing pin. DO NOT change the angle of the surface.

Polish the front face of the firing pin's sear engagement area. DO NOT change the angle of the surface where it engages the sear block.

Reduce the BOTTOM of the firing pin to slightly reduce length of trigger pull.
NOTE: As you've already discovered, you can't take much off.
When cutting the bottom of the firing pin, make the cut at a VERY slight angle to the back. (You want the front of the firing pin engaging area just slightly taller than the rear). This slight angle will provide clearance for the firing pin to cleanly clear the sear block.

REMEMBER, these parts are casehardened. Cut through the coating, and the part is ruined.
You CANNOT "see" if you break through. This will expose soft metal, and the part will wear to an unsafe condition quickly.
Old 01-23-2005, 09:52 AM   #3
Join Date: Mar 2003
Posts: 39

Great suggestions. That is the help I needed.

I know that the Thompson was never meant to have a crisp, silk smooth target rifle trigger pull but as I posted before, the pull on this firearm was so horrendous that one would think that the safety was still on.

By the way, I just received a new firing pin from Kahr. I was pleased that they shipped it so quickly. It's unfortunate that it's the wrong one. I ordered the long tip and they shipped a short tip. I'll give it another try.

Thanks for the information.

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