Tuning Umarex M1A1 Thompson Repair

[ninersix]

Looking good! I think you’ll know right away if the rate of fire has slowed down. If not enough so, next step I’d explore would be locating a slightly lighter spring.
Welcome the the league of tinkerers, this is the fun stuff!

I have not found a way to access the spring yet. I take out all six(6) screws and three pins and nothing happens. It is a journey.
By the way, "born2fly", are you or have you been a pilot; I suppose once a pilot always a pilot? Just wondering.

 

[borne2fly]

I have not found a way to access the spring yet. I take out all six(6) screws and three pins and nothing happens. It is a journey.
By the way, "born2fly", are you or have you been a pilot; I suppose once a pilot always a pilot? Just wondering.

I flew Cessnas and a Citabria years ago. Back then it was actually affordable. If I were a rich man I’d get a Grumman Widgeon

 

[ninersix]

My life has been fortunate not for money but experience, flown in many planes and Jets (civilian and military) Mike My life long friend and his Archer. We are planning to get together between our schedules and the weather.... We play our game plaster-of-Paris tanks and our WWII MP40, M1A1 and M3 Grease gun, we go at it and yes we have rules.
Great fun, after Whisky (the good stuff) and Cigars also the good ones. A couple of years ago I was heavier then.
Mikes Archer going to a Fly in with WWII Warbirds.
Buy the way I am on the left (wearing a replica of WWII Field Marshal Sir Harold Alexander, (Africa Core, British Army), Yes we dress up for battle.
Oh one more thing I ordered a chronograph so i can know what the RPM is and not guess.

 

[borne2fly]

My life has been fortunate not for money but experience, flown in many planes and Jets (civilian and military) Mike My life long friend and his Archer. We are planning to get together between our schedules and the weather.... We play our game plaster-of-Paris tanks and our WWII MP40, M1A1 and M3 Grease gun, we go at it and yes we have rules.
Great fun, after Whisky (the good stuff) and Cigars also the good ones. A couple of years ago I was heavier then.
Mikes Archer going to a Fly in with WWII Warbirds.
Buy the way I am on the left (wearing a replica of WWII Field Marshal Sir Harold Alexander, (Africa Core, British Army), Yes we dress up for battle.
Oh one more thing I ordered a chronograph so i can know what the RPM is and not guess.

View attachment 583507

Now THAT’s the life … good whiskey, cigars, and airplanes . Well done! I’ve never had much PIC time in low wingers, maybe someday.
Most of my airgun stuff is just for target shooting. My mock battles are reserved for swords … both modern and historical fencing. “Weapons for two and breakfast for one”, as they say

 

[ninersix]

Now THAT’s the life … good whiskey, cigars, and airplanes . Well done! I’ve never had much PIC time in low wingers, maybe someday.
Most of my airgun stuff is just for target shooting. My mock battles are reserved for swords … both modern and historical fencing. “Weapons for two and breakfast for one”, as they say

Ha ha ha (me laughing); we started with old Crossman pump air guns (after collage) and moved eventually to plaster of Paris tanks. It is so much actually destroying the tanks. It all started in collage in dorm rooms playing "Panzer Blitz' the board game. AND THEN UMAREX CAME OUT WITH AUTO WWII replica BB gun weapons. I should send you a few plaster tanks so you can feel the thrill. (They are painted... Look at the posted pictures Look at post #125 to see a few, I have 17 different models (targets) tanks and half tracks.
Anyway when the child dies inside of you than you are truly dead. I used to do fencing with sabers, saber foils, not swords I got pretty good.

Anyway I think I figured out to use a "felt" buffer pad to slow the action, they say (Amazon) will arrive tomorrow including the chronograph, I figure if I use the white metal and the doughnut it might work. Anything below 900 RPM is a win.

When my friend Mike fly's me to his house I will take some pics and movies

• #125

 

[borne2fly]

Ha ha ha (me laughing); we started with old Crossman pump air guns (after collage) and moved eventually to plaster of Paris tanks. It is so much actually destroying the tanks. It all started in collage in dorm rooms playing "Panzer Blitz' the board game. AND THEN UMAREX CAME OUT WITH AUTO WWII replica BB gun weapons. I should send you a few plaster tanks so you can feel the thrill. (They are painted... Look at the posted pictures Look at post #125 to see a few, I have 17 different models (targets) tanks and half tracks.
Anyway when the child dies inside of you than you are truly dead. I used to do fencing with sabers, saber foils, not swords I got pretty good.

Anyway I think I figured out to use a "felt" buffer pad to slow the action, they say (Amazon) will arrive tomorrow including the chronograph, I figure if I use the white metal and the doughnut it might work. Anything below 900 RPM is a win.

When my friend Mike fly's me to his house I will take some pics and movies

• #125

Those tanks do look pretty realistic. Good job! I built heaps of models as a kid, first the plastic kits and later the gas engine stuff. Had a lot of fun with all that. When I got a Dremel tool one Christmas I thought I had died and gone to Heaven ... it opened up a whole new world of possibilities. I've been a machine tool junkie ever since. And these days I'll use any excuse to chuck airgun parts onto the mill or lathe
I still routinely fence foil and epee during the week, but Saturdays are reserved for the stuff below. The rapiers have accompanying daggers which aren't shown. We call the sabers "Heavys" or "Heavy Russians" since they were made in Russia and are effectively real swords with rounded edges, not normal fencing sabers. In both cases we need to gear up with light kevlar/leather armor over our regular fencing gear. All this is normal HEMA competition stuff (Historical European Martial Arts).

 

[ninersix]

Those tanks do look pretty realistic. Good job! I built heaps of models as a kid, first the plastic kits and later the gas engine stuff. Had a lot of fun with all that. When I got a Dremel tool one Christmas I thought I had died and gone to Heaven ... it opened up a whole new world of possibilities. I've been a machine tool junkie ever since. And these days I'll use any excuse to chuck airgun parts onto the mill or lathe
I still routinely fence foil and epee during the week, but Saturdays are reserved for the stuff below. The rapiers have accompanying daggers which aren't shown. We call the sabers "Heavys" or "Heavy Russians" since they were made in Russia and are effectively real swords with rounded edges, not normal fencing sabers. In both cases we need to gear up with light kevlar/leather armor over our regular fencing gear. All this is normal HEMA competition stuff (Historical European Martial Arts).

View attachment 583624

View attachment 583625

I use Sabers with a saber foil.
If you want to see a bunch of tanks (plaster of Paris) get shot to heck check out on YouTube Mrdstony that was me shooting and see teste and an actual battel Mike and I had

Western Europe WWII Final​

A lot of tanks shot heck with edits and Music.

 

[borne2fly]

I use Sabers with a saber foil.
If you waht to see a bunch of tanks (plaster of Paris) get shot to heck check out on YouTube Mrdstony that was me shooting and see teste and an actual battel Mike and I had

Western Europe WWII Final​

A lot of tanks shot heck with edits and Music.

I like it. Fun stuff.
Do they have molds for the big Tiger tanks too?

 

[ninersix]

I like it. Fun stuff.
Do they have molds for the big Tiger tanks too?

They; you mean me.
I made the molds for 1/35 scale tanks, the masters for the tanks were made from my tank models that I put together, usually Tamaya kits. All tanks I cast and made are painted and I put the decals on.
The decals are made from scanned decals from the Kits and transferred to mailing labels.
Yes, I made the molds for the Tiger and Panther. I have 17 different molds; I made them all.

Fun... you should try them for targets, remember they are only plaster, they explode with grace, just like the real ones. Very much Fun.

 

[borne2fly]

They; you mean me.
I made the molds for 1/35 scale tanks, the masters for the tanks were made from my tank models that I put together, usually Tamaya kits. All tanks I cast and made are painted and I put the decals on.
The decals are made from scanned decals from the Kits and transferred to mailing labels.
Yes I made the molds for the Tiger and Panther. I have 17 different molds; I made them all.

Fun... you should try them for targets, remember they are only plaster, they explode with particular grace, just like the real ones. Vert much Fun.

View attachment 583679

Ahh, that’s right, you did say that you made the molds. That’s excellent work, I must say! I have never done much with plaster other than make a big mess. I’m guessing the treads are from the original kits and get re-used?

 

[ninersix]

Ahh, that’s right, you did say that you made the molds. That’s excellent work, I must say! I have never done much with plaster other than make a big mess. I’m guessing the treads are from the original kits and get re-used?

The plaster mold is taken from the original model tank tread. Yes, it can be messy, but a sheet of plastic and large syringes make it easy to inject the plaster, clean the excess and much less messy.
So Nope, they are also molded - this time from a re-enforced plaster mold using a large tube of Silicone rubber squeezed into the mold half and then put together, 30 min later the new tread.

My "Wall Of Victory"!

 

[borne2fly]

The plaster mold is taken from the original model tank tread. Yes, it can be messy, but a sheet of plastic and large syringes make it easy to inject the plaster, clean the excess and much less messy.
So Nope, they are also molded - this time from a re-enforced plaster mold using a large tube of Silicone rubber squeezed into the mold half and then put together, 30 min later the new tread.

My "Wall Of Victory"!

View attachment 583683

That’s quite a process! I like those sorts ofprojects. I do have some casting experience, mostly sand casting automotive parts, but very little with the intricacies of models. I’m not sue my old eyes could capture all that fine detail.

 

[ninersix]

A1

That’s quite a process! I like those sorts of it is not that projects. I do have some casting experience, mostly sand casting automotive parts, but very little with the intricacies of models. I’m not sue my old eyes could capture all that fine detail.

Well it is not that hard, after all the masters are already made, that is the hard part. I use a silicone RTV molding material it comes in gallon kits. I do not even need a vacuum to pull bubbles out of it, and yes it is cured in 4 hours.
For seeing I use those magnifiers that you put on your head, it even has a light.
By the way my offer is still on the table I will send you a couple of tanks (free of charge) if you want them. We can figure how to exchange address but--- "NOT on an open forum." I am a Cyber security guy after all. I will send you a message on the secure channel that they have on this forum.

 

[borne2fly]

A1

Well it is not that hard, after all the masters are already made, that is the hard part. I use a silicone RTV molding material it comes in gallon kits. I do not even need a vacuum to pull bubbles out of it, and yes it is cured in 4 hours.
For seeing I use those magnifiers that you put on your head, it even has a light.
By the way my offer is still on the table I will send you a couple of tanks (free of charge) if you want them. We can figure how to exchange address but--- "NOT on an open forum." I am a Cyber security guy after all. I will send you a message on the secure channel that they have on this forum.

I do appreciate the offer. Thank you. But we’re in the middle of downsizing right now. The place is bursting at the seam and we’re unloading stuff left and right. Seems we spent half our lives collecting it all and now we’ll spend the over half getting rid of it

 

[ninersix]

I do appreciate the offer. Thank you. But we’re in the middle of downsizing right now. The place is bursting at the seam and we’re unloading stuff left and right. Seems we spent half our lives collecting it all and now we’ll spend the over half getting rid of it

I get it, no worries.

 

[ninersix]

Well I have determined and organized a test that will determine I can slow the RPM rate of fire for the Umarex M1A1 Thompson BB gun. Leaving the weights and a felt (buffer, not sure I have the right felt material that's why the test); any way I have a personal busy day today lots of family coming over including a puppy! So I doubt I will be able to get to it today. I am not sure the buffer is in the correct position so again the test.
Will share the results and photos when I have them.

 

[borne2fly]

How’s that M1A1 mod going?
Curious to know how much the firing rate slowed down

 

[ninersix]

How’s that M1A1 mod going?
Curious to know how much the firing rate slowed down

bornet2fly: I tested and with the weight and the buffer pads (felt) based on my calculations a slowdown of about 75rpm. That is not an exact number but a good guess. I did test all three combinations e.g. just the pads, then just the weights and finally both together.
The chronograph I bought does not work (not for BBs at least) and I am returning it. conclusion of the test is a failure; looks like I will have to take the upper half of the M1A1to gain access to the main bolt spring.
I noticed that all of my mags (all 4 of them0 were not catching the sliding bolt and continued to dry fire. I looked at them and it appeared that the follower in the mags appeared to be shorter. They appeared to be "worn down" and thus not lifting the sear enough the catch the top of the bolt (upper half of the Thompson).
I will also half to fix the mags by lengthening the sear follower (the thing on the spring that lifts the sear and stops the upper bolt.
I have already ordered a new magazine to compare.
All of my M1A1 mags are at least 5 years old, I must have shot 10K worth of BBs at full auto thru most of them. I did some research and found that all of the Umarex magazines have these wear issues; I posted a new thread on the forum about it. So far my MP40 and M3 do not show any of this wear.

 

[borne2fly]

bornet2fly: I tested and with the weight and the buffer pads (felt) based on my calculations a slowdown of about 75rpm. That is not an exact number but a good guess. I did test all three combinations e.g. just the pads, then just the weights and finally both together.
The chronograph I bought does not work (not for BBs at least) and I am returning it. conclusion of the test is a failure; looks like I will have to take the upper half of the M1A1to gain access to the main bolt spring.
I noticed that all of my mags (all 4 of them0 were not catching the sliding bolt and continued to dry fire. I looked at them and it appeared that the follower in the mags appeared to be shorter. They appeared to be "worn down" and thus not lifting the sear enough the catch the top of the bolt (upper half of the Thompson).
I will also half to fix the mags by lengthening the sear follower (the thing on the spring that lifts the sear and stops the upper bolt.
I have already ordered a new magazine to compare.
All of my M1A1 mags are at least 5 years old, I must have shot 10K worth of BBs at full auto thru most of them. I did some research and found that all of the Umarex magazines have these wear issues; I posted a new thread on the forum about it. So far my MP40 and M3 do not show any of this wear.

I agree, the next step would be to try a lighter spring. This might cause the bolt to blow back faster, in which case I’d want to have that recoil buffer installed.

The cone valve (in the part that directs gas into the barrel) has a *very* light spring, and I suspect this spring has everything to do with when & how much CO2 goes out the barrel before the valve slams shut and redirects the gas to blow the bolt back. I’ve never had to fiddle with this spring, but it seems that a slightly stiffer spring (or possibly a small spacer under the existing spring) would send more gas out the barrel and less to blow back the bolt. In that case, a weaker bolt might be required to guarantee the gun will cycle. And all this would stack up in the right direction to slow the cycle time.

I think the bolt in the M1A1 might be a bit smaller than the one in the MP40? I was able to add enough lead to the MP40 bolt to slow the rate of fire to around 450rpm.

 

[ninersix]

I agree, the next step would be to try a lighter spring. This might cause the bolt to blow back faster, in which case I’d want to have that recoil buffer installed.

The cone valve (in the part that directs gas into the barrel) has a *very* light spring, and I suspect this spring has everything to do with when & how much CO2 goes out the barrel before the valve slams shut and redirects the gas to blow the bolt back. I’ve never had to fiddle with this spring, but it seems that a slightly stiffer spring (or possibly a small spacer under the existing spring) would send more gas out the barrel and less to blow back the bolt. In that case, a weaker bolt might be required to guarantee the gun will cycle. And all this would stack up in the right direction to slow the cycle time.

I think the bolt in the M1A1 might be a bit smaller than the one in the MP40? I was able to add enough lead to the MP40 bolt to slow the rate of fire to around 450rpm.

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.