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Bolt Hold Open Lever For 1927a1


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#1 Whiskey Brother

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Posted 03 December 2005 - 04:33 AM

I've examined my 1927A1 closely, looked at the pictures, disassembled mine, and am still puzzled about the modifacation to semi's that looks like the full auto switch, but is really just a bolt hold open lever.
How do you get that lever to hit the trip? It looks like it would go right through the disconnector. Do you have to modify the disconnector by drilling a hole in it or something? And does the lever operate the trip? Or is it hitting the pawl? Anyone got a picture of what the new part looks like?

I'd like to get one of those if somebody makes them. If not, I've made bunches of stuff for my guns over the years and feel confident I could make one myself, provided I can figure out how to get around the disconnector...
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#2 kilroyjones

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Posted 03 December 2005 - 09:22 AM

I am currently modifying my Kahr to look more like an original Tommy. I have a Savage 1928 trigger frame mounted to my Kahr.

You must mill the disconnetor, sear and pawl to allow clearance for the selector switch. On a Kahr frame you would also need to drill the holes in the trigger frame for the selector. The selector shaft has steps in it, so the trigger frame hole on the right side is much smaller than the hole on the left side. Hope that sort of made sense, you need to look at a selector in person and you will understand.

The selector shaft also has a small cam that lines up close to the hold open pawl. My thinking is a "L" shaped piece of metal coming down from the pawl. The short arm of the L would be under the cam. When the switch is rotated the cam would move the L down and at the same time pull the pawl with it.

This right now is just idea and theory, I haven't made an actual working part yet. I know Damon at Tommygunner has a custom made pawl, but I don't know if he would sell just the parts. Hopefuly PK or Damon will reply, or some other RKI. I know only enough to be dangerous unsure.gif
KJ


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#3 TommyGunner

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Posted 03 December 2005 - 09:44 AM

Whiskey Brother, Kilroy,

user posted image

user posted image

This is the milled pawl that we produce. You can make one by soldering a washer on the side of the existing pawl and notching it in the mill. The coil spring has to be pretty strong. The key to the wire spring is in the knotch that you must cut. The spring must not bottom out against the back side of the notch or it will just bind...it must have a full range of motion to work.

Kilroy basically outlined the rest. Just my .02. on the semi frame mod...don't modify the selector when you can modify the semi frame. Preserve vintage parts before semi parts. May take a little tweaking with the springs. On the full auto frames you would have to shim to internals to fit correctly. Hope this helps.

Damon
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#4 kilroyjones

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Posted 03 December 2005 - 11:25 AM

Damon, thanks for the picture. The idea I had was completely backwards.

Whiskey, I should also add that you can get the book "New production semi-autos" from Doug Richarson. It gives details and demisions to convert the Kahr internals to work with the selector. The book does not cover the bolt hold open device. You can get contact info for Doug from the FAQ.

You might consider (true tommy collectors cover your ears..) getting an original 1928 trigger frame to replace the Kahr frame. The 28 already has the selector hole and markings, plus the detachable stock. Save you from some extra work. KJ
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#5 Whiskey Brother

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Posted 03 December 2005 - 11:47 AM

Thanks for the replys guys. Back in the early '90's after I got my gun, I bought a bunch of spare parts from Doug Richardson and got one of his catalogues at the Great Western Gun Show in Kalifornia. (Before the LAme-o city council banned it anyway.) I still have that catalogue, is his contact information still the same?

I knew the disconnecter and pawl had to be modified for this, what about the pivot plate? Do I need to get the full auto style pivot plate? It would be simple to make up a jig to drill the hole in the right place if the pivot plate is the full auto one, and on this kind of operation I'd rather make a jig and have that hole in the right place.

I don't know why they didn't just put the hole in the bolt handle slot in the right place so alls you have to do is pull back and up on the bolt to lock it back. (Did they ever do that?) On mine it gets within a 1/4 inch and then stops. I guess when they added that 1/4" in the back of the receiver for the 1927 semi's, that was the only way batF-Troop would allow it, or something....
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#6 Zamm

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Posted 03 December 2005 - 01:14 PM

Whiskey Brother,
Indeed, the early first production semi's had a smaller second hole
in the reciever so you could pull up on the bolt handle and lock it back.
Never worked well, and they went to the little flip switch in the mag channel after about a year or so.
Here's a photo of mine that still retains the now useless second hole.
Best, Z
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#7 Whiskey Brother

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Posted 03 December 2005 - 01:33 PM

I guess there really is nothing new under the sun... rolleyes.gif

Why didn't it work? Did it have a tendancy to slip or did it lock back halfway through a mag?

I'm also curious about the magazine follower. If WWII production XXX mags were meant for full auto M1A1s, and if the trip lever located in the magazine well was not even invented until the West Hurley semis, than why do all my WWII XXX mags have a projecting stud on the follower to hit the trip on the last shot?

Was this something planned, coincidence, or just luck?
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#8 TommyGunner

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Posted 03 December 2005 - 02:54 PM

Whiskey Brother,

Yes you would need the full auto pivot plate and to drill the third axis in the frame. Both ways will work but on the 1927 models installing the 1928 frame will fetch the added benifits of having the selector hole already in place, accepts the detachable buttstock and 1928 rear grip. At this point you would be a barrel contour and gripmount away from being able to accept GI wood. Unless, that is, if you were putting on a vertical foregrip..then no barrel contour is needed but a change to 1/2" gripmount may be needed depending on what is originally on the gun. Hope this helps.

Damon
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#9 Whiskey Brother

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Posted 03 December 2005 - 03:09 PM

Actually, I'm not looking to make my gun look like somebody elses gun, I just want something more convienient than sticking a piece of metal up the magazine well to hit the trip when I shoot the drum. It's inconvieneint to have to go through all that just to take the empty drum out. That lever seems to be just the thing to make it easier for magazine changes.

I can honestly say that I prefer certain of my guns to reflect my personality, and not that of a historical gun or whatever. My Thompson I know is different from every single other one ever produced, just because mine is the only one that has it's particular checkering pattern on the wood, my handmade vertical foregrip sling swivel, it's own distinctive hand made rear sight, adjustable for windage, and other little things that I've done to it in the 15 years I've owned it. (Even an "Accessory" rail on the barrel for lasers, lights, stereo, or digital camera if I so choose.. tongue.gif )

There are some failed experiments that have come off the gun, like my Red LED forward sight that lit up when you pressed a button on the forward hand grip, -that one worked great until about 40 rounds went through the gun and knocked the wire loose everytime. And of course the year or so that my gun wore a Harris folding bipod on it until I realized that it made it heavier and I never shot it from the bipod...

Point being, my gun is MY gun, and it happens to be one of the funnest ones I own, and the one I spend about 80% of my time at the loading bench for. Which is where I should be now if I want to go shoot this afternoon...
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#10 Zamm

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Posted 03 December 2005 - 04:33 PM

QUOTE
Why didn't it work? Did it have a tendancy to slip or did it lock back halfway through a mag?


In my opinion, it was just a bad design. You had to pull that cheese grater all the way back, then lift it up a bit and let it foward to lock into the small hole. When ready to cock, you pulled back and let go of the bolt, hoping that the cheese grater would drop down and allow the bolt to slide home. If you know about those incredibly tight springs, plus the nasty grating action of the bolt charging handle, well, you get my meaning. It was a task to lock that bloody thing back. Also, the metal on the reciever channel quickly started to get sharp and worn in the vicinity of the small hole. Bad set-up.

QUOTE
If WWII production XXX mags were meant for full auto M1A1s, and if the trip lever located in the magazine well was not even invented until the West Hurley semis,


No, the original Thompson full auto designs all had the mag trip. Remember, these where the early semi designed frames, just for the 27A1 and they did not incorperate the trip in them at first. They even screwed with the magazines so that after the last shot the bolt would slam home and ride over the modified mag follower. I was surprised when I first shot a 30 round GI mag and the bolt slamed into the follower after the last cartridge! Nasty!
See picture of early West Hurley Modified 20XXmag
Best, Z
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#11 LIONHART

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Posted 04 December 2005 - 02:08 PM

The First WH I ever owned, was a '75 Model. The Frame Internals were quite different. Actually, I prefered that system to the later, but the rumor I heard was when or if the Gun was dropped with the Bolt locked back on a loaded Magazine, it could slam the Bolt forward firing a round. Never happened to me though.
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#12 Zamm

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Posted 04 December 2005 - 04:08 PM

Lionhart,

Don't know if it would have fired, but quite a few times I thought I
had that pesky thing locked only to have it slip out ( probably from not being pulled up enough to engage fully the second hole, along with the massive sprong tension) and ram home. Allmost lost me bloody finger cleaning the breech that way!
I finally resorted to braking the thing down for any type of cleaning or upkeep.
Z
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#13 choppero

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Posted 04 December 2005 - 06:39 PM

I recently completed 5 hold open jobs on as many guns. I was able to get very positive lock back of the bolt only after making modification to the selctor. I agree with Damon that the original parts are too valuable to modify. I did feel a little guilty but to have the positive locking needed to keep the bolt from slipping, it needed to be done. I have since milled some very good replacement selectors that can be seen at http://www.hudsontra...Parts/index.htm.
I hope this will help keep the real parts only for the originals.

Tom
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#14 dokkerdam

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Posted 12 July 2017 - 06:16 PM

I know you're talking about open bolt full autos but have had any experience with the bolt lock slipping on the Kahr semi-auto Thompsons, specifically an aluminum TA5 pistol (though the problem is that the notch in the bolt and the hold open lock edge are both starting to round over - with only 250 rounds since new - at least it's not related to the aluminum receiver).

 

I'm thinking I might need a new bolt at only 250 rounds - or at least some machining which I can't do.  NOT HAPPY!

 

dokkerdam


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