Thompson 1927A-1 firing pin issue

[texasgunlover]

I picked up a used Thompson semi auto and for some reason the firing pin isn't striking hard enough to get reliable performance. Half the time it doesn't strike hard enough. The primers are barely dented. I took it apart and examined all parts, it doesn't seem to have any obvious major defects. The tip of the pin has a small gash to one side.

What I find very odd is the shape of the firing pin hole in the bolt face. It is not a round hole. The entire oblong pin slides through quite far. See attached pic 101 for the hole. The rest show the pin all the way through. You can see the tiny defect in the tip. The last pic is from a youtube video showing how to disassemble the gun. Notice that its bolt and pin are like every other gun I have ever seen: they are round, not oblong.

I hope you old timers have some experience with this gun and can tell me wtf I am dealing with.

Thanks in advance,

Texas Gun Lover

 

[Hog killer]

I picked up a used Thompson semi auto and for some reason the firing pin isn't striking hard enough to get reliable performance. Half the time it doesn't strike hard enough. The primers are barely dented. I took it apart and examined all parts, it doesn't seem to have any obvious major defects. The tip of the pin has a small gash to one side.

What I find very odd is the shape of the firing pin hole in the bolt face. It is not a round hole. The entire oblong pin slides through quite far. See attached pic 101 for the hole. The rest show the pin all the way through. You can see the tiny defect in the tip. The last pic is from a youtube video showing how to disassemble the gun. Notice that its bolt and pin are like every other gun I have ever seen: they are round, not oblong.
View attachment 2001075 View attachment 2001076 View attachment 2001084 View attachment 2001085
View attachment 2001086

I hope you old timers have some experience with this gun and can tell me wtf I am dealing with.

Thanks in advance,

Texas Gun Lover

Looks like in 3 rd photo it has slight bend to it but might be angle of photo
Can you push it down by finger pressure? If it is slightly bent it might be dragging a little and like you said most I have seen were round not oblong if it is dragging littl it won’t let the pin strike hard enough to fire the primmer is it centered on primmer or off set?

 

[Hog killer]

Looks like in 3 rd photo it has slight bend to it but might be angle of photo
Can you push it down by finger pressure? If it is slightly bent it might be dragging a little and like you said most I have seen were round not oblong if it is dragging littl it won’t let the pin strike hard enough to fire the primmer is it centered on primmer or off set?

I just blew up your photos and clearly your pin is not round at all put rectangular with a small round tip you might try to clean the fire pin spring really good and blow out with air could have debris in spring causing it to stick some

 

[Hayata]

Dang, now I'm going to have to go look at mine...I think round...broke the firing pin once trying to bump fire the ol' girl...and had to replace it but for the life of me the pin is round.

 

[MRM]

That bad boy for sure has the distance.
I'd be looking for a new spring.

 

[MuleShoe]

SOUNDS LIKE WEAK FIRING PIN SPRING !

 

[StuP]

I seem to remember my Auto Ordnance had a firing pin like that, but that was quite a few years ago.

 

[texasgunlover]

I seem to remember my Auto Ordnance had a firing pin like that, but that was quite a few years ago.

Thanks for all the suggestions. As for the weak strike, I figured out there's a part missing--the hammer--I didn't notice on disassembly. So will replace it and give it a try.
The shape of the firing pin hole is something I have never seen, and I would like to know if anyone else has seen one like it.

 

[texasgunlover]

Follow up Report: It was the missing hammer. After installation, the gun shoots very reliably. The firing pins odd rectangular shape is apparently the way it was designed.