Tuning Umarex M1A1 Thompson Repair

[borne2fly]

born2fly: Yeah I have been looking at the exploded parts diagram to plan the disassembly but that will have to wait, I have some traveling to do in the next two weeks; including our annual get together with my friend. So I will keep you posted.


: I noticed that all of my mags (all 4 of them0 were not catching the sliding bolt and continued to dry fire. "Referenced from above.
This was just the sear not meeting the upper "bolt" correctly; this is the real problem with the Umarex M1A1.
Cheap ass design of the Taiwan engineers. Using a Steel sear which hits a soft "white metal" cast stop; cheap but REALLY STUPID, BAD, BAD engineers.
For anyone's information, the Umarex Legends BB/pellet guns are all made with mostly cast "White Metal"
I will eventually fix that next probably with a 606T aluminum or a little steel block stop in the gun, I haven't decided yet.
One problem at a time.

Even though I have had to do some slight repair (After @11,000 BBs) My favorite BBs gun is still the Umarex M1A1 Thompson.

Yes … they’re all made of white metal. And doomed to wear out rather quickly. Fortunately we can use the existing parts as patterns to make proper replacements as you suggested, and end up with something that will last.

 

[ninersix]

Yes … they’re all made of white metal. And doomed to wear out rather quickly. Fortunately we can use the existing parts as patterns to make proper replacements as you suggested, and end up with something that will last.

Thank born2fly.
I am going on the 6th year (guessing... could be longer) with my M1A1 and at least 11K BBs thru it probably more judging by the large full box empty co2 cartridge's. With wood furniture... as I wrote before; "it is my favorite BB gun. I am thinking about getting another one and making some more "Kit videos" on how to improve and stabilize to gun indefinitely and making the kits to sell for those who want to keep them working.

 

[borne2fly]

Thank born2fly.
I am going on the 6th year (guessing... could be longer) with my M1A1 and at least 11K BBs thru it probably more judging by the large full box empty co2 cartridge's. With wood furniture... as I wrote before; "it is my favorite BB gun. I am thinking about getting another one and making some more "Kit videos" on how to improve and stabilize to gun indefinitely and making the kits to sell for those who want to keep them working.

The more I think about this, the more I think the right solution might be to modify the cone valve.
I’m thinking that the bolt needs to move rearward more slowly but still slam forward with enough momentum to activate the poppet valve. That sounds a bit like the way a shock absorber works. Not sure if I’d want to try making such a thing for this application.
Alternatively, perhaps modify the cone valve so that it does not close completely, but permits some gas to leak out the barrel instead of redirecting it all to push the bolt back (a small spacer behind the delicate little cone valve spring might work). Less gas pushing the bolt would mean slower rearward travel. Just so long as it gets back far enough to reset the trigger. Forward travel would not change, as it would still be governed by the bolt spring.
I’m just brainstorming …