Page 1 of 2 12 LastLast
Results 1 to 10 of 14

Thread: Broken Buffer retaining pin

  1. #1
    Join Date
    May 2015
    Posts
    61
    Feedback Score
    0

    Broken Buffer retaining pin

    Any idea what causes this?

    Mine sheared off yesterday. New rifle (a build not factory). About 200 rounds through it.

    I ordered a lost parts kit from Bushmaster that has 2 retaining pins and 2 retaining pin screws plus the take down pin and spring that the back plate keeps in place. Brownells had individual parts available also. Colt and DPMS.

    Any idea what causes this? I have an H buffer in carbine stock. Cycled reliably up to now. Pin moved up and down normally to install/remove the buffer and buffer spring prior to breaking off.

    Probably just a random occurance but thought I'd ask.

    Thanks!

  2. #2
    Join Date
    Feb 2014
    Posts
    396
    Feedback Score
    3 (100%)
    What's your buffer look like? Is there dents/scratches around the rim?


    Sent from my iPhone using Tapatalk

  3. #3
    Join Date
    Feb 2015
    Posts
    154
    Feedback Score
    8 (100%)
    What about your bolt carrier? How does it look?

  4. #4
    Join Date
    May 2015
    Posts
    61
    Feedback Score
    0
    thank you both for prompt reply.

    lahunter, yes there is a faitly deep indent on one of the two flat portions of the buffer face. It looks almost like it was peened. Definately a sharp strike with something to cause it. The other flat has a faint abrasion on one side but the edge is a bit thicker than normal, it's flared out a bit. Glad you suggested I look closely. I was going to keep it but will replace it now. Th face of buffer looks like new.

    masenomics, the bolt carrier slot at 6 o'clock and the back face of carrier look like new. No damage there.

    When the bolt carrier returned to battery it did not quite lock up all the way. I reloaded and fired one more time before it happened again. So buffer was un-restrained for two shots. I finally opened rifle and realized what had happened.

    PS I have a Syrac gen 2 adjustable gas block on this rifle and I usually shoot suppressed. I turn it down 2 clicks when shooting with the can. So I dont think I am over gassed, but wonder if I should try a slightly heavier buffer? this H buffer weighs 3.8 oz. I see that some are4.1, 4.6 and H2/3 over 5 oz. Any suggestions?
    Last edited by 556x45; 06-29-15 at 14:43.

  5. #5
    Join Date
    Dec 2012
    Location
    NW WA
    Posts
    348
    Feedback Score
    1 (100%)
    When you close the upper onto the lower, does the back of the bcg make contact with the buffer?

  6. #6
    Join Date
    Oct 2013
    Posts
    1,587
    Feedback Score
    10 (100%)
    Quote Originally Posted by 556x45 View Post
    Any idea what causes this?

    Mine sheared off yesterday.
    Something is out of spec. The only time the retainer should catch the buffer is when you remove the upper.

    All other times the carrier is in contact with buffer holding it off retainer.

    Retainer slot may be a little long. If it broke one and has a mark(s) on buffer face, it will break another.

    Leave retainer broken and just catch your buffer/spring when you open it up.

    I run my carbines without buffer retainers so there is one less thing to break and go who knows where.

  7. #7
    Join Date
    Feb 2014
    Posts
    396
    Feedback Score
    3 (100%)
    Quote Originally Posted by 556x45 View Post
    thank you both for prompt reply.

    lahunter, yes there is a faitly deep indent on one of the two flat portions of the buffer face. It looks almost like it was peened. Definately a sharp strike with something to cause it. The other flat has a faint abrasion on one side but the edge is a bit thicker than normal, it's flared out a bit. Glad you suggested I look closely. I was going to keep it but will replace it now. Th face of buffer looks like new.

    masenomics, the bolt carrier slot at 6 o'clock and the back face of carrier look like new. No damage there.

    When the bolt carrier returned to battery it did not quite lock up all the way. I reloaded and fired one more time before it happened again. So buffer was un-restrained for two shots. I finally opened rifle and realized what had happened.
    I think I may know what happened. I think your lower may be slightly out of spec. When you hinge the rifle closed, observe the interface between the tail of the bolt carrier and the buffer. The bolt carrier should make contact with the face of the buffer and push it back slightly, taking the pressure from the buffer off of the retainer. If your lower is out of spec then it could allow the buffer to impact the retainer and eventually break it. That's why I asked what your buffer looked like.

    With that being said, you don't need a buffer retainer for the rifle to function and I suspect if you replaced it then it would only be a short amount of time before it broke again.

    You'll need to replace it to find out if that's the issue though.


    Sent from my iPhone using Tapatalk

  8. #8
    Join Date
    Feb 2014
    Posts
    396
    Feedback Score
    3 (100%)
    Quote Originally Posted by lahunter57 View Post
    I think I may know what happened. I think your lower may be slightly out of spec. When you hinge the rifle closed, observe the interface between the tail of the bolt carrier and the buffer. The bolt carrier should make contact with the face of the buffer and push it back slightly, taking the pressure from the buffer off of the retainer. If your lower is out of spec then it could allow the buffer to impact the retainer and eventually break it. That's why I asked what your buffer looked like.

    With that being said, you don't need a buffer retainer for the rifle to function and I suspect if you replaced it then it would only be a short amount of time before it broke again.

    You'll need to replace it to find out if that's the issue though.


    Sent from my iPhone using Tapatalk
    Edit: looks like a few people beat me to it haha


    Sent from my iPhone using Tapatalk

  9. #9
    Join Date
    May 2015
    Posts
    61
    Feedback Score
    0
    Great advice. You guys are better than a You Tube video!

    I will need a new buffer retainer pin to trouble shoot.

    This is a high quality billet lower by Bomberg but I think the stock extension tube may have been screwed too far forward. Whats left of the buffer pin still moved up and down but the edge of the tube looks like it is awfully close to the pin stud. I checked two other rifles and the rear of BCG does touch the buffer face when you swing it down to close. So I know what to look for now, and did not before.

    Leaveammo to me. The rifle did not go into battery without the retainer pin holding the buffer face in position. thats why I knew something was wrong? Guess I can try it without the retainer pin once I back off the end plate and extension nut.

    I am using a Colt upper, and there is some side to side play in the upper so I installed an accu wedge that tightened it up.

  10. #10
    Join Date
    Oct 2013
    Posts
    1,587
    Feedback Score
    10 (100%)
    Quote Originally Posted by 556x45 View Post
    Leaveammo to me. The rifle did not go into battery without the retainer pin holding the buffer face in position. thats why I knew something was wrong? Guess I can try it without the retainer pin once I back off the end plate and extension nut.

    .
    Sounds like your broken retainer tip got into the mix, the whole reason I don't use retainers.

Page 1 of 2 12 LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •