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Buffer Disintegration

1928 Buffer

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#1 Ville28

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Posted 26 May 2019 - 09:59 PM

I was shooting my PKd WH 1928 today and after breaking it down for cleaning discovered the buffer had disintegrated. It is probably 4-5 years old. Has anyone else experienced this and should even the more modern buffers be changed every few years? The gun is only shot at most about 2000 rounds per year. Thanks in advance.Attached File  74A4F331-B6D0-4DA0-B76E-578B3F8110B6.jpeg   170.91K   16 downloads
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#2 Bridgeport28A1

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Posted 27 May 2019 - 05:25 AM

I experienced the same type of failure. I now inspect and change my buffers on more regular basis. My failed buffer looked similar identical to your buffer pieces. Board member mnshooter was with me when it failed.


Edited by Bridgeport28A1, 27 May 2019 - 10:08 AM.

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#3 TD.

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Posted 27 May 2019 - 08:55 AM

Ville28,

Thanks for the post. Is that a Diamond K disc? If so, It is the first one I have seen disintegrate like that.

 

I always recommend the Diamond K discs; one for your Thompson and one for a friend whose disc ends up like the one you posted while at the range! 


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#4 Ville28

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Posted 27 May 2019 - 10:58 AM

Yes - It is a PK disc probably 4-5 years old. I didnt realize these were susceptible to disintegration. I have reached out to PK and will get a few to have some on hand. It really worried me that I didnt realize it had failed until after I broke the gun down for cleaning.
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#5 reconbob

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Posted 27 May 2019 - 11:44 AM

Easy for me to say but not so easy to remember to do....

Plastic/urethane will deteriorate over time due the the effect of air, light, and solvents.
If you would have checked this as part of your standard cleaning routine I will bet that you
would have noticed the disc to have become crumbly and wax-like as opposed to the rubbery
flexibility it had when it was new. It appears from the photos that if you would have removed
this from the buffer pilot and bent it to test its flexibility that it would have broken in two.

I learned this a while back when I had a new factory suppressor for a Military Armament
Corp M-10 submachine gun. The wiper was a urethane quite similar to these buffers which
was integrated into a threaded, knurled cap for easy replacement. Anyway I sold the gun but
not the suppressor which sat around for a few years and one day I looked at it and the urethane
wiper had turned into a chalky crumbly substance which completely disintegrated when I poked
It with my finger.

Bob
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#6 Paladin601

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Posted 27 May 2019 - 12:10 PM

Just like Cement, plastic hardens as it gets older. Sometime the catalyst is a little more or less can change the aging process. Heat and contaminants can do the same as well as the age of the products mixed to make the part.


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#7 timkel

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Posted 27 May 2019 - 03:52 PM

I had the same problem with those buffers. This pic shows what I found after a day of shooting. Later I checked 4 others of the same buffer still new in a plastic bag. They were all stuck together like puddy and useless. I could not remember where I got them.
Bad-Buffer.jpg
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#8 reconbob

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Posted 27 May 2019 - 05:23 PM

The last buffer disk I got from PK was a rubbery black material. It was
for his M1921 buffer but I would assume he uses the same material for his
M1928 buffers and quite likely is a better material.

Bob
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#9 timkel

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Posted 27 May 2019 - 05:49 PM

I have also have a few buffers from Keystone arms. These are a harder material and show no signs of deterioration yet. FYI..I went back to using original buffers after finding the bad buffers.
keystone-Buffer003.jpg
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#10 reconbob

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Posted 27 May 2019 - 08:18 PM

A couple of thoughts -

Are these plastic/rubber/urethane buffers a solution to a non-existent problem?
Under normal conditions in original (Colt, Savage, Auto-Ord) guns I have never seen
or known of a buffer to break or of a receiver to crack at the tail which is said to be
what these buffers protect against.
I know there is a photo out there of a receiver with a cracked tail but I thought
it was a West Hurley and may have been abused by the high rate of fire modifications
advocated by Gunmachines in the late 1970's-early 1980's - and this certainly is not
"normal" conditions.

What is the effect of one of these "soft" buffers on rate of fire? My guess would be
that it would reduce the rate of fire by slowing the rebound of the bolt. But, could it be
the opposite and speed up the bolt and increase the rate of fire? Or would the rate of
fire be the same and confuse us all? Anybody ever put once of these on an ROF
detector?

Bob
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#11 john

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Posted 27 May 2019 - 08:23 PM

Bridgeport28....was the failed buffer you experienced from the material you got from me?
That was high durometer(88?) urethane sheet and I've had a buffer made from that (1/8" ) in my gun for close to ten years...maybe 7-8k rounds?
Also one in my SW76 and my STEn mkII, both with similar round counts.

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#12 mnshooter

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Posted 27 May 2019 - 09:27 PM

The above mentioned urethane has held up fine for me, too.

I found that this style buffer will somewhat increase the ROF with a Smith 76. 

Of course, that's a direct blowback, fixed firing pin.  Hmmm, just like a M1A1. 

Have not measured this in 28's.  

Need to get some firing tests, with a couple of the shooters listed above.


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#13 Bridgeport28A1

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Posted 28 May 2019 - 06:36 AM

john, the failed amber colored buffer was not the urethane buffer material I got from you.
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#14 Bridgeport28A1

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Posted 28 May 2019 - 06:46 AM

mnshooter, if bring your PACT timer along on our next shoot and we could test rate of fire with the different types of buffers installed. I will bring an amber PK buffer, black PK buffer and a hard red USGI buffer.
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#15 laurencen

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Posted 28 May 2019 - 10:53 PM

it is not typical for urethane to disintegrate due to weather uv exposure and oils, the unique characteristics are excellent chemical and wear resistant,  I have molded many shapes of urethane of different hardness's and yet to see a product fail as the one pictured, years ago I made a buffer for the 1928, just at that time the gun laws changed and since then its a safe queen often oiled but never to fire again.

 

there are a few of the buffers around, if anyone wants to give them a try I will did them out


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#16 Paladin601

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Posted 28 May 2019 - 10:58 PM

where is Buzz when he is needed


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#17 PK.

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Posted 29 May 2019 - 09:19 AM

The old fibre buffer disks are all pushing a century of age and are not ‘off the shelf’ anymore, that is why new discs are made.  Polyurethane is an excellent material for the reasons Laurencen listed.  If you look at the photo provided by Ville28 you can clearly see where cracks formed long before it ‘disintegrated’, it has been my experience that the material will crack and not crumble when/if it fails.  The part depicted by Timkel was not made of polyurethane; I examined these for him and can state that definitively.

The buffer disc is there to isolate a metal to metal hammering and prevent damage to the steel, it is a sacrificial part and should be inspected with regular cleaning and replaced when cracks become evident.


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#18 bug

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Posted 30 May 2019 - 09:13 AM

All of this concern got me looking at my 21 buffer. I wasn't happy. The polyu discs I got from Glen W many years ago are in bad shape. My question is, does anyone have specs on the original disc stacks used in the 21?  I'm looking for diameter and thickness. The GW discs seem to have been 3/8" dia. The bore of the buffer tube could handle 7/16" it seems. What are folks who shoot 21 configuration using in the original buffer tubes?  TIA

 

Bob D

 

PS  I'm leaving for an MG shoot tomorrow and would love to use the 21 set up.


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#19 Motorcar

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Posted 30 May 2019 - 09:31 AM

it is a sacrificial part and should be inspected with regular cleaning and replaced when cracks become evident.

 

Thanks for adding your professional insight PK.

 

I'm still successfully running your "black" buffer in my '28 for years now, with two of your "peach" ones on the shelf ready to go.

 

"Should be inspected", always when it comes to firearms.


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#20 bug

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Posted 30 May 2019 - 09:36 AM

I got a pic of the 21 stack.

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