Page 3 of 9 FirstFirst 12345 ... LastLast
Results 21 to 30 of 81

Thread: 16” midlength vs 20” rifle length bolt life

  1. #21
    Join Date
    Mar 2011
    Location
    Mid-West, USA
    Posts
    2,811
    Feedback Score
    63 (100%)
    Quote Originally Posted by ta0117 View Post
    I understand higher pressure means greater wear on the parts, but it’s not necessarily linear especially when you get above or below certain levels.

    I know BCM Filthy-14 broke a bolt at 16k rounds, but then you see bolts like DD or LMT (not the reliability enhanced one) lasting up to 20k on carbine gas M4s. Has anyone actually broken a rifle length M16 bolt?
    Happened at an event I was at. To be fair, it was probably not that bolt's first barrel, and I don't know how much of a factor the pressure of M855A1 plays into it. The team members there considered the M16A4's bolt breaking a far rarer event than the broken M9 locking block that occurred at the same training event.

  2. #22
    Join Date
    Jan 2019
    Posts
    2,584
    Feedback Score
    1 (100%)
    Quote Originally Posted by ta0117 View Post
    I understand higher pressure means greater wear on the parts, but it’s not necessarily linear especially when you get above or below certain levels.

    I know BCM Filthy-14 broke a bolt at 16k rounds, but then you see bolts like DD or LMT (not the reliability enhanced one) lasting up to 20k on carbine gas M4s. Has anyone actually broken a rifle length M16 bolt?
    Wasn't Henderson getting like 40k rounds on Colt bolts?

  3. #23
    Join Date
    Mar 2015
    Posts
    1,756
    Feedback Score
    0
    Quote Originally Posted by ta0117 View Post
    I know BCM Filthy-14 broke a bolt at 16k rounds . . .
    And, if it were cleaned every 1,000 rounds or so, they probably could have replaced the bolt before it broke.

    Sorry, my little soap box issue.

    Cracks start life as microscopic, but they become visible to the naked eye a few thousand rounds or so before they actually break, if you take the time to clean off the gunk and look.

  4. #24
    Join Date
    Mar 2011
    Location
    Mid-West, USA
    Posts
    2,811
    Feedback Score
    63 (100%)
    Quote Originally Posted by lysander View Post
    And, if it were cleaned every 1,000 rounds or so, they probably could have replaced the bolt before it broke.

    Sorry, my little soap box issue.

    Cracks start life as microscopic, but they become visible to the naked eye a few thousand rounds or so before they actually break, if you take the time to clean off the gunk and look.
    Great point. It seems hard to get people to split the difference between fanatical cleaning regimens and never cleaning at all, but a little common sense goes a long way.

  5. #25
    Join Date
    Jan 2021
    Posts
    75
    Feedback Score
    0
    Quote Originally Posted by okie View Post
    Wasn't Henderson getting like 40k rounds on Colt bolts?
    IIRC the Colt bolt broke a lug at 26k rounds or so.

  6. #26
    Join Date
    Aug 2015
    Location
    Found a home.
    Posts
    1,145
    Feedback Score
    1 (100%)
    Quote Originally Posted by CPM View Post
    Almost no one reading this post will ever wear out a bolt or barrel.
    With current ammo prices? More right than ever...

  7. #27
    Join Date
    Jan 2019
    Posts
    2,584
    Feedback Score
    1 (100%)
    Quote Originally Posted by ta0117 View Post
    IIRC the Colt bolt broke a lug at 26k rounds or so.
    I went back to that thread and looked, and last I could find they were at 30k rounds without breakage, vs the average 20k rounds he quoted for others. I want to say though that there was an update somewhere when one finally broke, and I want to say it was somewhere around 40k rounds. I might be making that up entirely, but I could almost swear I remember that.

    In any case, 50% longer bolt life is pretty good in a milspec bolt. It's not a massive thing if we're talking 16 inch carbines, but when you start shortening that barrel things get wonky fast. For SBRs, I think Colt is the only logical choice. As far as I know, they're still the sole supplier of bolts for Mk18s.

  8. #28
    Join Date
    Jan 2021
    Posts
    75
    Feedback Score
    0
    Quote Originally Posted by okie View Post
    I went back to that thread and looked, and last I could find they were at 30k rounds without breakage, vs the average 20k rounds he quoted for others. I want to say though that there was an update somewhere when one finally broke, and I want to say it was somewhere around 40k rounds. I might be making that up entirely, but I could almost swear I remember that.

    In any case, 50% longer bolt life is pretty good in a milspec bolt. It's not a massive thing if we're talking 16 inch carbines, but when you start shortening that barrel things get wonky fast. For SBRs, I think Colt is the only logical choice. As far as I know, they're still the sole supplier of bolts for Mk18s.
    I checked the thread and it’s a single Colt bolt that lasted very long and he even said himself it’s the exception, not the norm, and usually Colt bolts last as long as DD and LMT, which is still about as good as it gets.

    https://www.ar15.com/forums/AR-15/Hi...ge=24#i7343147
    Last edited by ta0117; 04-30-21 at 20:57.

  9. #29
    Join Date
    Feb 2011
    Location
    USA
    Posts
    2,351
    Feedback Score
    2 (100%)
    Quote Originally Posted by ViniVidivici View Post
    Moreover, the slightly accelerated parts wear becomes moot if you remain aware, keep a round count, and inspect/replace wear components according to an appropriate maintenance schedule.
    Back when I was new to the forum I tried to get the people who called themselves experts or professionals or insiders to tell me what an appropriate preventative maintenance schedule on a bolt in a carbine gas 16" would be.

    I never could get an answer out of anybody. Just "until it breaks there's no such thing as PM on a rifle" or "you won't get there".

    Have things changed?

    Is there some kind of a guideline or consensus on how long a "it has to work" bolt in a high stress application should be trusted?

    Let's say my run of the mill BCM bolt in a suppressed SBR running full power 5.56 with an oversize BCM gas port that operates violently. How many rounds till you (anybody) would go ahead and swap that bolt?

    Or is it still "you can't break an AR15 bolt"?
    Last edited by Warp; 04-30-21 at 21:07.

  10. #30
    Join Date
    Aug 2017
    Location
    Lowcountry, SC.
    Posts
    6,175
    Feedback Score
    30 (100%)
    Quote Originally Posted by Warp View Post
    Back when I was new to the forum I tried to get the people who called themselves experts or professionals or insiders to tell me what an appropriate preventative maintenance schedule on a bolt in a carbine gas 16" would be.

    I never could get an answer out of anybody. Just "until it breaks there's no such thing as PM on a rifle" or "you won't get there".

    Have things changed?

    Is there some kind of a guideline or consensus on how long a "it has to work" bolt in a high stress application should be trusted?

    Let's say my run of the mill BCM bolt in a suppressed SBR running full power 5.56 with an oversize BCM gas port that operates violently. How many rounds till you (anybody) would go ahead and swap that bolt?

    Or is it still "you can't break an AR15 bolt"?
    Dave Merril wrote a thing about that a while back. What bits to replace, and when. Like 2010-2015 era. Don’t remember where. Good practice to replace springs periodically, particularly the extractor springs. I had two extractor spring failures last year. One on a rifle gas 18”, where the spring snapped and the gun kept sticking cases (in pouring rain, of course), the other in a 11.3” with LMT enhanced bolt, where the springs weakened over a couple years of heavy use and I started having stoppages. Both guns suppressed. It would be reasonable to swap extractor springs at 4-5k, ejector spring, cam pin, extractor spring and extractor at 8-10k, extractor spring at 12k-15k, and maybe check FP protrusion and headspace once in a great while.

    Personally, as far as the bolt itself, I’d shoot it until it breaks or until you note cracks in cleaning. Or it fails headspace. Although, I don’t clean my personal stuff much. In actual practice I tend to semi-retire my rifles annually, and only shoot them rarely after that. Between 5k and 15k, with many of my friends doing the same, intentionally or otherwise. I haven’t seen a bolt break in a while, actually.

    Most people shoot like a case a year or less of .223 pressure stuff. That dude can replace his bolt whenever he replaces the barrel in like 30 years, or whenever he realizes his shit won’t hit the berm and its not just the Sightmark this time. If you are launching M855 and Hornady Frontier erryday, at some point you have to consider that this is a probability game and: rotate the rifle into a training beater status, replace the bolt, or just don’t worry about it. And consider when to switch between those three options. You’ll have to draw that line yourself.

    Anybody have any data on headspace growth?
    Last edited by 1168; 05-10-21 at 11:36.

Page 3 of 9 FirstFirst 12345 ... 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
  •