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Thread: Cetme buffer experiment

  1. #1
    holescreek's Avatar
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    Cetme buffer experiment

    I previous posts I've said that in a properly tuned Cetme the carrier won't touch the buffer during live fire. Until today, it was just a hunch. I finished the 60 degree locking piece for my Cetme pistol build today and found a baggie of buffer parts from a project I started on many years ago but never finished. The pistol kicks like a mule so I thought I'd dive back onto the buffer project to see if it would help.

    My project consisted of removing the rubber components of a Cetme buffer and replacing them with a heavy die spring which would give a little less resistance but more travel after the carrier strikes the buffer anvil. In order to take advantage of the longer travel I had to make a longer anvil so the carrier would strike it sooner. A standard Cetme buffer anvil protrudes .300" from the face of the buffer. My first anvil protruded .340".

    20200627_135337.jpg

    In order to see if the carrier hit the buffer during firing I cut pieces of .063" diameter lead solder and taped it to the anvil face and buffer face then checked it after firing. The anvil face would obviously show first contact, the lead on the buffer face would show me if the carrier had bottomed out due to lack of spring pressure.

    20200627_145115.jpg

    I shot one round unsuppressed using the original 50 degree LP and checked the lead. It was not touched by the carrier. So I switched to the 60 degree LP and tried it again. No contact. The carrier never touched any part of the buffer.

    Since I had it handy I did the same test but fired suppressed this time. While shooting 50 degree suppressed the carrier hit the lead on the anvil enough to reduce it from .063" diameter down to .047" thickness. Shooting 60 degree suppressed smashed a new piece of lead down to .038" thickness.

    50 LP supp after.jpg

    While testing I did not notice any difference in felt recoil between the spring buffer and a rubber filled one. So that got me wondering why so many people spend money on "heavy buffers", commercial or otherwise. If the carrier doesn't touch it, what is it doing?

    After diner I went back into the shop and made an even longer anvil (.250" longer, sticking out a total of .69") for the buffer so the carrier would have to hit it and make a difference.

    I started over with the longer anvil, 50 and 60 degrees unsuppressed. Nothing. The carrier still didn't touch any part of the buffer. No change in recoil. So I screwed on the suppressor with the 50 degree LP in place. The lead on the anvil was smashed down to .028" thick so I know the anvil had to have pushed the buffer spring back at least .260" but I still didn't feel a difference in recoil.

    20200627_213417.jpg

    Somebody clue me in on what the advantage is to a heavy buffer. (especially if the carrier doesn't come close to hitting it without a suppressor?)
    Granted, this test was done on a pistol with a 10.5" barrel, but the weapon was cycling as normally as any rifle would have with the proper locking piece.
    Last edited by holescreek; 06-27-2020 at 11:43 PM.

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    scottz63's Avatar
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    I put a heavy buffer in my PTR and it made a bit of difference in felt recoil. If I remember right, I think the anvil sticks out .600
    14EH AIT Instructor-PATRIOT Fire Control Enhanced Operator/Maintainer

  3. #3
    holescreek's Avatar
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    Quote Originally Posted by scottz63 View Post
    I put a heavy buffer in my PTR and it made a bit of difference in felt recoil. If I remember right, I think the anvil sticks out .600
    I may extend my experiment to my test rifle today just to test my theory. But so far I doubt your carrier has ever touched the buffer. It's easy to check with some solder and electrical tape.

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    holescreek's Avatar
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    I modified the test Cetme rifle to accept the modified buffer I used in the pistol test. Then shot suppressed and unsuppressed with 50 and 45 degree LP's since those are used in standard Cetme's and H&K/PTR rifles. I also remeasured the exposed anvil length and found that it was only protruding .600" from the buffer face.

    DSCF7730.JPG

    Firing suppressed the lead was smashed pretty well, indicating that the buffer was struck. Now I need to figure out a way to see how far the anvil actually moved. I know it didn't bottom out because the lead on the face wasn't touched.

    You can see in the chart that firing unsuppressed the lead was slightly grazed while using both LP sizes. Grazed but not smashed. So unless your buffer anvil is sticking out at a minimum of .663" (on a Cetme) the carrier isn't touching the buffer.

    I wonder if there is a difference in strength between a used Cetme carrier return spring and a new PTR spring?

    Since I'm messing with buffers today I might make some even longer anvils to play around with.

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    Hmm...It sure felt like less recoil after I installed the heavy buffer. Maybe the placebo affect? I'll have to go measure the anvil on mine. I also have a Bill Springfield heavy buffer kit installed in my wood stock, it too has an extended anvil.

    Buffer7.jpg
    Last edited by scottz63; 06-28-2020 at 04:03 PM.
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    Senior Veteran nevada's Avatar
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    My cetme is a soft shooter. If the carrier isn't hitting the buffer I'm surprised. Would that be why G3's have a rep for stiff recoil? Why doesn't the carrier hit the buffer?
    RRRROOOWWWRRR PHHT PHHT I AM THE FORCE!

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    Good question nevada. Why are the buffers there if the carriers don't even touch them?


    Holescreek, just measured the anvil on my PTR heavy buffer. It sticks out .657 from the face. My carrier is definitely hitting it as the anvil has a small wear mark on it where it did not when I installed it. I did not measure the Bill Springfield anvil yet, it's installed in my PTR right now and I'm getting ready for work. I'll measure it in the morning.
    Last edited by scottz63; 06-28-2020 at 04:30 PM.
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    holescreek's Avatar
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    I made a new anvil that stuck out .77" from the buffer face, put the lead on it and balled up some aluminum foil and wedged it between the buffer and the anvil.

    20200628_172442.jpg

    Using the Cetme pistol I took one shot unsuppressed with the 60 LP then disassembled and discovered that the carrier hadn't touched either the lead or the foil. So I screwed the suppressor on and fired again. This time the lead was smashed to .011" and the foil was crushed flat to a thickness of .404". That means when firing suppressed the buffer is moving .359".

    20200628_172838.jpg

    20200628_173116.jpg

    I've already got my test rifle torn down or I'd do the same with it.
    Last edited by holescreek; 06-28-2020 at 05:51 PM.

  9. #9
    holescreek's Avatar
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    Quote Originally Posted by nevada View Post
    My cetme is a soft shooter. If the carrier isn't hitting the buffer I'm surprised. Would that be why G3's have a rep for stiff recoil? Why doesn't the carrier hit the buffer?
    In my opinion the buffer is only used as a last resort. Either to stop a carrier in a rifle that has just fired a grenade or a carrier with a defective bolt locking lever.
    Remember all those defective rifles that have roller dents in the rails in the back? That's because the carrier was hitting the buffer. It's typically caused by bad locking levers or their springs or a bad bolt head ramp.

    That said, since I made the longer buffer anvil for the test I'm probably going to grind it down some so the carrier doesn't hit it so hard when firing suppressed. I don't want dimpled rails.

    I think HK's have stiffer recoil because they are over-gassed with a 45 degree LP. They should be running on 36~40 degree LP's.

  10. #10
    Senior Veteran nevada's Avatar
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    I wonder how many people - like me - have bought the buffer replacement internals to keep the gun running smoothly? LOL!
    I thought the old rubber parts looked so good I've kept them, in oil, in a plastic bag.
    RRRROOOWWWRRR PHHT PHHT I AM THE FORCE!

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