Who has broken a bolt with a mid-length gas system?

[KevinB]

The military has tables on this. I believe it suggested about half again as long.

Performance Spec for Bolt life is 5k on the rifle (M16).
Last time I looked I was pretty sure the M4 has the same.

That said I know a lot of entities that use 3,500 for the Mk18 and M4.

[kgwld1]

Mine is now a secodary but has 15 k and change it heavy f/n barreled 16 inch. Shoots very well still but I have just f myself I'm sure as Murphy may own it now. Doh.

[PatrioticDisorder]

KAC built 16" Midlength (Armalite style middy gas 1:7 Wylde Chambered Douglas SS barrel)



I had over 18k thru it -- using LMT Improved Bolt.
Used in Canada, US, Afghan and Iraq.
Sold it as it could not leave Iraq - buddy who got it put another 5k before the barrel was utterly toast, bolt did not fail.
Had a spare Colt M4 bolt in the MIAD, but never needed.

Ammo used
Swiss GP90 (3,000)
CF issue C77 ball (3,500)
HandLoad 75gr (500)
Handload 77gr Nosler (750)
Georgia Heat 55gr (5,500)
Federal GM 69gr (1,500)
M855 (1,500)
Mk262 Mod0 and Mod1 (2,500)
M995 AP (aprox 75 rds)

Most was shot semi-auto, however around 14 mags where fired auto back to back out the back of our CAT vehicle (GPMG went down hard) and 2 mags of Mk262 where fired auto for function testing when I got a bunch of it available.

20 rds of M995 where fired for function (delinked SAW Black belts), and 2 28rd mags where fired after.

Big Red's LT 16" middy Stealth had around 12k thru it IIRC, before he opted for M79 and Mk18

Just to clarify, you used the LMT enhanced bolt? Also wanted to bring this thread back from the dead to see if anyone had any updates on their bolts from their middys.

[VIP3R 237]

I have 25k through a Cryptic Coatings Black Mystic BCG from two mid length gas barrels. No issues yet.

[tom12.7]

I'm not doubting the results, but I would be more interested in how they compared to the normal Colt?

[MegademiC]

*paging markm* how many rounds and what gas length on your digested NiB bolt?

[Cap'n Crash]

I'm not Mark, but had the same NiB bolt. Lost 4 lugs at less than 1500 rounds. Midlength BCM- not blaming the rifle. Assuming the cause was the NiB coating, as discussed in other threads. Vendor replaced the bolt without issue.

[AKDoug]

I went 7500 on my DD M4V7 middy.. At that point I replaced the bolt simply as a preventative maintenance precaution. I replaced it with a Colt bolt. There were no outward signs of excessive wear on the bolt, so I put it in my spare parts bin.

[T2C]

I own two carbines with mid length gas systems, one of them I carried on duty. Neither has broken a bolt, but I replace them somewhere between 10,000 and 12,000 rounds.

[Iraqgunz]

I have yet to "break" an actual bolt. The last bolt that "broke" was due to bad ammo. At that time it had roughly 12-14K on it and it was a BCM 12.5" URG with a suppressor. The bolt itself actually survived, but the extractor was completely done.