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Old July 8, 2019, 05:48 AM   #1
PJHeck
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Buffer material for 1921 Thompson.....

I am changing my 1928 guns over to 1921 internals. I have three sets of home made replica parts in hand. The '21's I have have a reddish cylinder of material in what I am calling the main spring guide. Mine are hard as rocks.!!!! Cant have much buffering value, if any...... I have made up one set of parts using a really stiff 7/16 dia spring. I would like to come up with something more toward the original set up in at least one of the others.

Any ideas on what material and/or where to get such...??????

PJH
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Old July 8, 2019, 01:27 PM   #2
Jim Watson
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Hard and red sounds like phenolic.
My FLG liked Delrin, it's not going to FEEL soft, but might be enough to buffer.
I think the various add on buffers these days are made out of polyurethane.
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Old July 8, 2019, 08:49 PM   #3
raimius
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Have you checked the Forgotten Weapons site? I know Ian did videos on each model within the past year or so. He might have mentioned the material.
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Old July 9, 2019, 12:55 PM   #4
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Quote:
The '21's I have have a reddish cylinder of material in what I am calling the main spring guide. Mine are hard as rocks.!!!! Cant have much buffering value, if any......
Be not so certain. I can't tell you about the Thompson from personal experience, but I can tell you that the buffer of the M2 .50BMG is a stack of reddish discs, that are "hard as rocks". Even the brand new discs are hard as rocks. NOT spongey, or flexible at all. And, they aren't supposed to be.

Your "buffer" MIGHT have been softer and hardened with age, I do not know, but I suspect it never was "soft". Take a look at where it is, and how it works.

Its not like the buffer of an M16, exactly, its more like the end tip of the M16 buffer, a hard (to the touch) resilient material to absorb the very last bit of bolt thrust, preventing metal on metal contact. It's "hard" so it lasts, but its considerably softer than steel.
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Old July 9, 2019, 07:59 PM   #5
PJHeck
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OK.........here is where I am now.........local machinist suggested looking in McMaster/Carr catalog. They have polyurethane rods of differing "stiffness".......range from 20 to 90. designations. I am going to try an 80 rod. Brian at BRP told me they use polyurethane material for buffers.

Most buffer material I have handled seem far too hard to do any buffing.....so apparently their use isnt like a buffer spring in a MG 42.

PJH

Last edited by PJHeck; July 10, 2019 at 07:34 AM.
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Old July 9, 2019, 09:59 PM   #6
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Buffers used in firearms cover a range of different functions and constructions. Some are essentially solids designed to "take a hit", without damaging steel on steel contact. Others can range up to various kinds of springs and/or hydraulic cylinders designed to slow down moving parts before stopping them.

See if you can find some kind of non-destructive testing that will give you some reference of the "hardness" of the old buffer you have, compared with the grades of modern materials.

Good Luck!
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Old July 10, 2019, 09:37 AM   #7
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I have a ton of Delrin and Turcite material. I can send you some n/c. Just throw me a few bucks for shipping. Pm me.
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Old July 10, 2019, 01:23 PM   #8
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The lads here argue about it all the time. Seems neoprene is a favourite buffer material. Neoprene has the advantage of being inexpensive and easy to come by.
http://www.machinegunboards.com/foru...hp?showforum=3
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Old September 6, 2019, 07:37 AM   #9
PJHeck
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Up & running....

A local machinist came up with a neat idea. He made a spring guide, left the front end of it thicker, threaded it 8/32, put an allen screw in with a spacer & a really stiff spring from a auto transmission valve body. I have not tried it but seems neat.......

I have one gun finished, used one of the above rods w/.120 thick washer (??) of the polyurethane from Mc/Carr at the rear end. I have .180 space between the flange on the rear piece (??) & the flange on the spring guide. The bolt was making prints on the front of the flange, so I cut a 1/8 square washer from a sheet of poly & put it between the flange & the spring. All seems well, shot over 1000 so far w/no issues, incorrect buffer material seem to be holding up as hoped.

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