Semi Modifications

[PaulJicha]

I see several gunsmiths online offering to modify semi auto "Thompsons" to disassemble without the need for a tool, as well as another mod that allows a selector switch to be added that operates the bolt catch so a drum can be installed and removed without the need for a third hand tool.

 

Are there specific instructions available anywhere online on how to perform these?

 

Thanks.

[T Hound]

I see several gunsmiths online offering to modify semi auto "Thompsons" to disassemble without the need for a tool, as well as another mod that allows a selector switch to be added that operates the bolt catch so a drum can be installed and removed without the need for a third hand tool.

 

Are there specific instructions available anywhere online on how to perform these?

 

Thanks.

 

 

Well, the only tool you need is a flat head screwdriver. But if you are bound and determined, there are sites

online here and there. But first I would check the threads here going way back. I have only got half-way thru

them so far, but there are interesting things here and there.

 

As for the bolt hold open modification, well I was given to understand that was on the Full-auto trigger frame

and not the semi-auto. That's not to say that it couldn't be done, but I'm willing to bet your going to have

to do a fair amount of machining/rearranging since the semi-auto parts are not exactly the same as the

full auto parts. You see the FA has the selector switch to work with/modify. But the semi-auto, obviously,

does not. That's a problem.

 

That said, you could always just use a finger to push the trip lever up and mimic an empty magazine. But,

brother, watch out when you let it go. Put my finger too high once and got it chewed.

 

DOVE

[PaulJicha]

The only other sites I have found discussing these modifications were gunsmiths offering to do it. The specific one, which I won't mention, has been over three months in dealing with, and just ordering parts has been like pulling teeth, so the chances of ever seeing my gun again after sending it for the work are nil.

 

Also, I can't really see one using a finger to work the bolt stop to remove a drum, unless your finger is a half inch wide and six inches long to reach up through that small space.

[PaulJicha]

There is one poat on the toolless frame removal bit but the description is based mostly on photo links that are no longer good.

[T Hound]

There is one poat on the toolless frame removal bit but the description is based mostly on photo links that are no longer good.

I definitely read your post wrong-about the third hand that is. Thought you wanted to hold the bolt open. Should have read slower. But most of

what I said stands. I don't know of any modification for a third hand device using the selector switch if your Thompson is semi-auto, simply because

it does not have a selector switch in place.

 

As for the tooless removal, a Dremel tool session in the correct place could do the trick, but it also may make your Thompson liable to malfunction

during the cycle. The problem with the SA is that the frame latch catches the sear. And so you have to use a flat head screw driver to lift it up (realizing

you may already know this) So the theory goes if you file the sear down enough then the latch will clear the sear and no tool is needed. I think this

is a bad idea however. What seems more likely to happen is that the firing pin fails to catch and then you will have the pin slamming and pinning

the cartridge on the ramp before it goes into battery.

[Gio]

For tooless removal of the reciever from the lower the proper way is to cut about 1/4" off the rear rails of the reciever. Their is post on this forum on this. If you are not proficient in gunsmithing I would recomend having a gunsmith do this.

 

You will need a 28 lower to eliminate the third hand when using a drum.

 

Both can be done a work great. good luck.

 

Frank

[reconbob]

I am not sure, but I believe you can drill/bore a semi-frame for the full auto rocker

pivot (selector). And modify the parts to have the eccentirc lobe on the rocker pivot (which

lifts and lowers the rocker on a full auto when it is rotated to single or full) lift the bolt

latch creating a bolt hold open feature for the semi.

If you want to keep the bolt to the rear to load a drum you can push the front end of

the trip up with your finger (and its not difficult to keep you finger out of harms way) while

you are cocking the gun. The lifting of the trip will lift the bolt latch which will engage

the bolt and hold it to the rear. Now you can insert the drum. To chamber a round pull

the bolt to the rear far enough to disengage the catch and let it run forward.

 

Bob

[mnshooter]

I am not sure, but I believe you can drill/bore a semi-frame for the full auto rocker

pivot (selector). And modify the parts to have the eccentirc lobe on the rocker pivot (which

lifts and lowers the rocker on a full auto when it is rotated to single or full) lift the bolt

latch creating a bolt hold open feature for the semi.

If you want to keep the bolt to the rear to load a drum you can push the front end of

the trip up with your finger (and its not difficult to keep you finger out of harms way) while

you are cocking the gun. The lifting of the trip will lift the bolt latch which will engage

the bolt and hold it to the rear. Now you can insert the drum. To chamber a round pull

the bolt to the rear far enough to disengage the catch and let it run forward.

 

Bob

 

The finger works for locking open before inserting the drum; the difficult part is locking the bolt open for drum removal.

Even with very strong hands, the strong semi factory springs make drum removal difficult without the bolt locked open.

The piece of plastic Kahr ships with the guns slips behind the drum to push the trip with the drum in place.

Dan -Deerslayer- Block is one who can do the selector/bolt hold open modification on semis.

[PaulJicha]

Loading the drum is easy, using the method thats been described. The trick is removing it. Since you can't get to the bolt stop with the drum in place, you need to hold back the bolt and work the magazine catch with one hand while sliding out the drum with the other.

[PaulJicha]

Sorry, I was just typing that as the other post was made saying the same thing.

 

If the toolless frame removal affects reliablity than I can deal with needing a flathead. Thanks for the advice on that.

[Joe H]

 

If the toolless frame removal affects reliablity than I can deal with needing a flathead. Thanks for the advice on that.

 

Paul,

 

Modifying the rails will in no way affect reliability. All it does is allow the frame to drop off before the frame latch hits the sear.

 

Here are some links to modifying the 1927A1:

 

http://www.machinegunboards.com/forums/index.php?showtopic=13560

 

http://www.machinegunboards.com/forums/index.php?showtopic=13713&st=20

 

Reconbob is right you can modify a 1927a1 frame for using the FA selector as a bolt hold open. It will require drilling the frame in the correct location, milling a pocket on the inside of the frame, a new FA selector, a new FA pivot plate, making the new hold open parts, and modifying the pawl, disconnector and sear to clear the new selector. Not a job for a novice.

 

Joe

[Chromebolt]

There is one poat on the toolless frame removal bit but the description is based mostly on photo links that are no longer good.

I definitely read your post wrong-about the third hand that is. Thought you wanted to hold the bolt open. Should have read slower. But most of

what I said stands. I don't know of any modification for a third hand device using the selector switch if your Thompson is semi-auto, simply because

it does not have a selector switch in place.

 

As for the tooless removal, a Dremel tool session in the correct place could do the trick, but it also may make your Thompson liable to malfunction

during the cycle. The problem with the SA is that the frame latch catches the sear. And so you have to use a flat head screw driver to lift it up (realizing

you may already know this) So the theory goes if you file the sear down enough then the latch will clear the sear and no tool is needed. I think this

is a bad idea however. What seems more likely to happen is that the firing pin fails to catch and then you will have the pin slamming and pinning

the cartridge on the ramp before it goes into battery.

 

I'm not sure what you're talking about her. Cutting the 1/4 inch from the rail will allow a tooless removal. It has nothing to do with filing down the sear.

[T Hound]

There is one poat on the toolless frame removal bit but the description is based mostly on photo links that are no longer good.

I definitely read your post wrong-about the third hand that is. Thought you wanted to hold the bolt open. Should have read slower. But most of

what I said stands. I don't know of any modification for a third hand device using the selector switch if your Thompson is semi-auto, simply because

it does not have a selector switch in place.

 

As for the tooless removal, a Dremel tool session in the correct place could do the trick, but it also may make your Thompson liable to malfunction

during the cycle. The problem with the SA is that the frame latch catches the sear. And so you have to use a flat head screw driver to lift it up (realizing

you may already know this) So the theory goes if you file the sear down enough then the latch will clear the sear and no tool is needed. I think this

is a bad idea however. What seems more likely to happen is that the firing pin fails to catch and then you will have the pin slamming and pinning

the cartridge on the ramp before it goes into battery.

 

I'm not sure what you're talking about her. Cutting the 1/4 inch from the rail will allow a tooless removal. It has nothing to do with filing down the sear.

 

Well, I did not know about that modification. Good to know! But it will, I imagine, leave a quarter-inch hole on both sides that you will have to live with? I keep learning interesting new stuff on this forum all the time. Thanks!

Edited March 22, 2012 by T Hound

[PaulJicha]

I would imagine this is referring to taking material off of the inner rail. Dont see how that would be visible when the piece is assembled.

[Chromebolt]

Try this modification. I did this on my semi and it makes a big difference

 

. http://www.machinegu...r+modifications

 

Edited to add: Remove a little less than 1/4 in with a dremel and fine fit with a file. It took me about 20 minutes one Sat morning. Add some cold blue and it's not noticable.

Edited March 23, 2012 by Chromebolt