WH Thompson Running Too Good..

[Ryo]

After wiping, springs were looking shiny and clean. no rust on it. I twisted them out and checked the internals as well. No rust there either. I am thinking of replacing the spring anycase. I'm also thinking of replacing the sear since it could be worn a bit. Note I don't have an eye on how worn it is. Better safe than sorry.. and if it's fine then I would have a spare just in case. Probably pickup a few other parts just in case. Are there any specific parts other springs and sear that gets worn out?

[Ryo]

Well I got the replacement parts (NOS) from Phil. Looks like he's running out of some parts so I bought more than I need. Any case I replaced the sear and rocker.

 

Rocker: I haven't fired it yet, but I did see a improvement of the SEMI mode tripping the rocker.. however sometimes it would still ride over if I lift the actuator and slide the bolt forward. I didn't think a new rocker would fix it but I figured to put the new one in. Going to either have to mod the rocker to be higher so it would trip. Thought it was strange that mine had some impact damage at an angle.

 

 

The sear I replaced looked a bit worn when compared to the new one. I'm hoping that the new sear will stop the runaway when in F/A.

Edited June 24, 2021 by Ryo

[reconbob]

Yes, that slight beveling is all it takes for the sear to slide

out of contact with the bolt. But if the sear is worn the notches

is the bolt may also be worn.

Both the sear and the bolt are quite hard. That extra 0.030"

in the bolt pocket in the receiver allows the parts to batter each

other and this is just the type of damage you would expect but

I'd also expect the notch in the bolt to have similar wear.

Also, somebody mentioned having a good strong sear spring

which is also important.

 

Bob

[Ryo]

Bob, thanks for the info. I will double check. Fortunately I also bought a spare bolt from Phil. 👍

[Ryo]

Oh forgot to ask..

Are worn Sears and such just disposable or can I just grind it back to a sharp edge?

[Ryo]

So I cleaned cosmoline off the NOS bolt and installed it. It seems like it triggers the rocker more often than not. If I pull the trigger hard, it seems to me that it always gets tripped.. but if I do it softly, it sometimes doesn't trip the rocker.

Feels like I have a band aid to the problem.. I will have to run it to see if it really works.

 

If it stops doing the runaway issue, then I'll may add more material/height to the rocker with a Tig weld to solve the semi auto mode.

However the previous owner of the WH graciously offered to get help to EDM thin steel plate to try to reduce the receiver internal depth. Might be an experiment worth trying.

I can say I'm definitely learning more about Thompsons.

[reconbob]

I would not recommend trying to correct the receiver by welding. Welding

will make the thin cross section red hot which ruin the finish. Also I believe we

have established (PK or Dan will know for sure) that the WH receivers are made

from leaded steel and the lead vaporizes at steel welding temps and you get a

pitted weld.

What I would try is this - cut a piece of 0.020" shim stock to correct size. Polish

the "ceiling" of the inside of the receiver with medium emery cloth. Mix up some

plastic steel epoxy and put as thin a coating as you can on the ceiling of the receiver.

Using appropriate clamping such as a proper sized wooded block clamp/hold the

shim tightly against the ceiling of the receiver until it sets.

I have done successfully on a test basis on an improperly (by me) machined

receiver but not over a long test. BUT, this does no harm to the receiver (like heating

It to welding temp would) and if it does not work no harm has been done. You can

break up the epoxy by heating with a propane torch at safe lower temp. The temperature

at which you would blue is low enough (300 deg.) that the epoxy is supposed to withstand

it but in my tests, while the epoxy did not appear to be damaged the parts separated.

So, I have not done an exhaustive test, more like a basic or introductory test but the

results were promising and again the good thing is that if it doesn't work you can remove

the epoxy and no harm has been done.

 

Bob

[Ryo]

Thanks Bob.

I was planning not to weld at this point in time, or ever since I know it would damage the finish. However I was planning on doing the shim. As mentioned the original owner mentioned he might have a buddy who can EDM a piece that will fit in the area. I have to look at the channel to see how evenly it was milled. If I recall, it was a bit rough. Going to have to see if the high areas will cause the shim to be out of tolerance.

I will look at epoxying it in as you had suggested.

[Ryo]

So now I have a new sear, bolt, rocker, sear spring in my WH. As mention before it helped band-aid the issue, but wasn't 100% reliable in the SINGLE mode. Maybe 1 out of 10 fails to trip the disconnector when I lightly pull the trigger.

 

For a test, I took a 0.020" stainless steel sheet and cut it out to fit my receiver to see if adding the material would solve my problem. Unfortunately the sheet only went from the back of the receiver to a little passed the actuator knob opening. Now I can see that the rocker has 100% engagement with the bolt, this proves that the main issue is with the receiver depth. Very disappointing.

 

Okay I have a functional question about the SINGLE and FULL AUTO selector. Since I don't have one to test out, I was wondering if it is normal when the bolt if forward, it would be harder to flip the switch from FULL AUTO to SINGLE since it's trying to raise the rocker up against the bolt? I would think so since the rocker is in the upright positions, not toggled, hence not enough space to push it up. With the bolt back, it's easy, no problem. I just want to confirm this is normal. If this is normal then I have a forward path to fix my issue. Thanks.

[gijive]

So now I have a new sear, bolt, rocker, sear spring in my WH. As mention before it helped band-aid the issue, but wasn't 100% reliable in the SINGLE mode. Maybe 1 out of 10 fails to trip the disconnector when I lightly pull the trigger.

 

For a test, I took a 0.020" stainless steel sheet and cut it out to fit my receiver to see if adding the material would solve my problem. Unfortunately the sheet only went from the back of the receiver to a little passed the actuator knob opening. Now I can see that the rocker has 100% engagement with the bolt, this proves that the main issue is with the receiver depth. Very disappointing.

 

Okay I have a functional question about the SINGLE and FULL AUTO selector. Since I don't have one to test out, I was wondering if it is normal when the bolt if forward, it would be harder to flip the switch from FULL AUTO to SINGLE since it's trying to raise the rocker up against the bolt? I would think so since the rocker is in the upright positions, not toggled, hence not enough space to push it up. With the bolt back, it's easy, no problem. I just want to confirm this is normal. If this is normal then I have a forward path to fix my issue. Thanks.

RYO,

 

First of all, the selector switch is only intended to be moved while the bolt is in the cocked/rearward position. The selector was not intended to be used with the bolt forward. A review of any instructions on the Thompson, manuals, You- Tube videos, etc. would have made this perfectly clear. Secondly, the Thompson is not intended to be fired with a light trigger pull like target shooting with a rifle. The trigger is to be pulled with a firm steady motion to the rear, not jerked back, but a firm complete pull. It appears that some of your problems were caused by your own unfamiliarity with the Thompson and the fact that you purchased a West Hurley, that are known for their poor manufacturing specifications.

 

Used properly, it should work fine.

Edited July 20, 2021 by gijive

[Ryo]

Thank you gijive.

 

I actually do know that I am suppose to have a firm hold back on the trigger. I was just mentioning when I would see a failure from experimenting.

 

The selector however I wasn't sure. Without my shim, I could switch it easily switch between FULL AUTO and SINGLE with the bolt forward. With the shim, it wouldn't. I expecting it not be able to after adding the shim, but wanted confirmation. Thanks for confirming it.

 

The WH purchase was due to it being a really good price.

Edited July 19, 2021 by Ryo

[damifino]

My experience is limited to a WH semi auto only. So just thinking out loud here. Since the receiver is to deep. Would it be possible to add to the top of the bolt instead?

[Ryo]

I imagine it could be added to the actuator. I was thinking about doing that as another experiment.. I haven't looked at the ramifications of doing that.. aka where the wear points would occur.

[damifino]

The top of the actuator, between actuator and bolt, or top of bolt. Think about what would else would change. The decision would be to alter the easiest part to replace. If you are replicating the surface you are adding to, what else would be affected? All things to consider. Hope this helps.

[Ryo]

The top of the actuator, between actuator and bolt, or top of bolt. Think about what would else would change. The decision would be to alter the easiest part to replace. If you are replicating the surface you are adding to, what else would be affected? All things to consider. Hope this helps.

I think overall adding material to the receiver to reduce the depth is the best method since it would contact both the bolt and actuator. Adding material to bolt would be hard since it's very little material contacting the upper part of the receiver. Actuator is doable but I prefer to be able to replace it it with a new one when it gets worn out. Beside the true root cause of the whole thing is the machine work/depth of the receiver.

 

Thanks for your time and insight.

[SRT705]

Ryo, Did you ever get the problem you discussed worked out? The reason I am asking is that I purchased a complete Savage 1928 lower for my West Hurley, (to have as a back-up) and had the same problems you are mentioning. I contacted Deer Slayer and he mentioned it might be the depth of the bolt on the WH that was causing the problems. I dont want to do any welding on my WH or my Savage 1928 lower, but would be willing to swap out some of the lower parts if it has a chance of correcting the problem. Sorry this is so long after your intial post, but I just found it. Thanks in advance.