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Questions About West Hurley Model 1928


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#1 Robgunbuilder

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Posted 16 August 2010 - 11:43 PM

Hi All- I'm a new member and new to Thompsons in general. I purchased a West Hurley M1928 recently primarily for shooting. I've fired some 500rds through it and it functions flawlessly with stick and drum magazines. Interestingly, the bolt shows evidence of someone machining a rearward sear cut into it which apparantly stops the bolt from coming foreward when the bolt is in the foreward or closed position. This sear cut has the SAME PROFILE as the sear cut in the front of the bolt! With the bolt in the closed position, the sear can pop up into this ramped cut about .200. and stop where it contacts the machined ledge of the sear cut and stops just like on the foreward sear cut that runs the gun in the open bolt postion. This Third sear cut clearly isnt present on a std Military M1928 bolt. The cut has clearly been expertly machined into the bolt and seems to serve no function other than to stop the bolt from coming foreward once the trigger is released? Was this done potentially as a safety issue? With the bolt foreward, the safety can now be engaged vs with a GI bolt it can't. This bolt is blued except where it was clearly machined. The actuator shows evidence of grinding on the front of it to allow it to hit the hammer.The person I got the gun from never even knew this was done. Does anyone know anything about this type of modification? In any event I have removed all this stuff and replaced the internals with all GI parts.

Edited by Robgunbuilder, 17 August 2010 - 06:34 PM.

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#2 reconbob

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Posted 17 August 2010 - 09:35 AM

I think what you are refering to is the standard Thompson mechanism.
The Thompson bolt assembly has a small triangular shaped piece called
the hammer that pivots in the front of the bolt. When the bolt slams shut
the hammer contacts the front face of the bolt pocket and pivots pushing
the firing pin forward to fire the cartridge. The slot for this is precisely
machined in the front of the bolt.
I am going to guess that since you are new to Thompsons you and
your friend are confusing the later M1A1 bolt which has no hammer with
the original M1928 bolt.
It is unlikely that someone would machine a bolt in the way you
describe since, practically speaking, Thompson bolts are too hard to
machine. That slot was machined before the bolt was hardened.
Back when West Hurley made their Thompsons there were no breech
oilers available. It was a part that was impossible to find. So they made
and shipped the guns without them and as a matter of convenience told
everyone that the breech oiler was not needed. A standard breech oiler
should fit in the receiver and you should use one.
Welcome to the board!

Bob
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#3 Robgunbuilder

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Posted 17 August 2010 - 06:42 PM

Reconbob- Thanks for the reply and I think my original description was incorrect and misleading. What I'm attempting to describe is a THIRD sear cut in the BACK of the bolt that allows the safety to be applied with the bolt foreward. This sear cut is shaped exactly like the second one on the bolt with a ramp that as I understand it is for catching the sear in the case of underpowered ammo not cycling the bolt fully. This bolt was blued and the Third sear cut expertly machined into the bolt using a manual mill. Since the bolt was blued and only this new area is bright, I'm assuming they used a carbide endmill. Why someone would go to all this trouble is beyond me.-Rob
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#4 reconbob

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Posted 17 August 2010 - 07:12 PM

Aha. Now I get it. That cut in the bolt is so that you can put
the safety on SAFE with the bolt closed. The earlier bolts did
not have that, and you could drop the gun in such a way that
the bolt would move back far enough to clear the mag and feed
a round - and fire it when it returned forward - but not far
enough back to be held by the sear.
With tens of thousand of guns in the hands of troops I guess
this "drop gun misfire" was enough of a concern that they fixed
it in the M1 and M1A1 guns.With the bolt shut and the safety on
SAFE the sear and the bolt are locked - the sear can't drop and
the bolt can't retract.
Here we are years later and the risk of having a heart attack
if you drop your Thompson is probably greater than the risk of
an accidental firing...

Bob

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#5 Robgunbuilder

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Posted 17 August 2010 - 08:13 PM

Reconbob- Well Said! Yes with the third sear cut, the safety can now be engaged and the bolt wont move either. I read somewhere that the Brits did this to their bolts. Does anyone have any pictures? I think I can now breath easier. I'm always worried when I find evidence that some strange mod has been done to a gun unless it was me who did it!. In any event I've replaced all the internals with GI parts and added the bolt oiler. Thanks for the replies and sorry my original explanation was misleading.-Rob

Edited by Robgunbuilder, 17 August 2010 - 08:15 PM.

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