16” midlength vs 20” rifle length bolt life

[sinister]

The US Army Marksmanship Unit shit-cans a National Match across-the-course M16 rifle bolt after its third barrel, nominally about 7500-9000 rounds.

Figure on a carbine, mid-, or suppressed about the same or shorter -- unless you just want to keep shooting until you get a lug break off or the bolt breaking at the cam pin hole.

[okie]

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

The 60k round bolt was the outlier, but he was still getting 50% plus more life out of Colt bolts on a regular basis. Like I said, not a big deal on a 16", but it's the difference between predictable vs. random failure on an SBR. Anyone who's using any other milspec bolt in an SBR either doesn't know or is incapable of understanding why Colt keeps getting the Mk18 contracts.

[ta0117]

The 60k round bolt was the outlier, but he was still getting 50% plus more life out of Colt bolts on a regular basis. Like I said, not a big deal on a 16", but it's the difference between predictable vs. random failure on an SBR. Anyone who's using any other milspec bolt in an SBR either doesn't know or is incapable of understanding why Colt keeps getting the Mk18 contracts.

Where is he saying that? Literally he said Colt bolts were breaking in the same time frame as DD and LMT. At one point, he said that no bolt problems with Colt at 25-30k round mark but didn’t comment on how DD and LMT bolts were doing and when asked if Colt lasts significantly longer, he didn’t comment. In the beginning, he did say that at the 20k round mark, problems started appearing in bolts including DD and LMT, but there’s a lot more that goes into bolt life than just the bolt itself, including the types of round used. I think he initially used Wolf Gold and then switched to Magtech, which can have different pressure curves.

Based on numbers you may want to say that Colt bolts are lasting longer but the guy himself said that they last as long as DD and LMT. I think Colt makes a great bolt, but it’s not some secret that trumps DD or LMT.

Lastly, where are you reading that Colt keeps winning contracts for Mk.18 bolts? As far as I know the Block 2 and also the 10.3” URGI use the mil-spec M4A1 BCG, which is also made by FN and Toolcraft.

He still seems to update that thread, so I’ll go there and ask him myself.

[ta0117]

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?

What is up with Hornady Frontier? Are they notorious for high pressure?

[AndyLate]

What is up with Hornady Frontier? Are they notorious for high pressure?

The guys at Arfcom are forever blowing up their ARs with Frontier ammo.

I have 3 empty 500rd boxes that used to be full of bulk/repacked "M193" Frontier from a LGS, and I did not experience any issues.

Andy

[1168]

What is up with Hornady Frontier? Are they notorious for high pressure?

Some internet dudes had some rather significant kabooms with it. The 55gr 5.56 variety, IIRC. Allegedly Hornady was pretty dismissive of the whole thing, telling one dude not keeping his rifle clean enough caused it. At first I thought it was TOS being TOS, and out of spec chambers were expected, but I’m not so sure anymore. It seems that a bad lot may have gotten out, but I dunno.

I’ve shot a bunch of the 68gr 5.56 load and really like it. It chronos about the same as 70gr Brown Tip, and Barnes 70gr VORTX 556, which makes it the perfect “match” load for me. Also rather close in velocity to Fusion MSR.

[Warp]

ar15.com, which is where a person goes to find significant sample sizes and people posting pics and videos of the product(s) they are making claims about (whereas here I always felt was small samples sizes and "because I said so")...anyway, on ar15.com there is more than enough evidence that I was easily convinced not to buy any Hornady Frontier. I don't care if it was loaded at Lake City when Federal was operating it, and I don't care if the rounds in question were nominally/substantially similar to XM193...there are too many people posting too many similar over pressure signs and literal kabooms to ever put Frontier into any of my firearms. And it's not just 55gr it's also the heavier match bullets for multiple people as well. Sure, there are also plenty of people with no problems in a case or three...just as there are a plethora of people out there with that many rounds through their 'as good as' rifle with zero reported problems. Don't care.

Avoid Frontier ammo

[AndyLate]

ar15.com, which is where a person goes to find significant sample sizes and people posting pics and videos of the product(s) they are making claims about (whereas here I always felt was small samples sizes and "because I said so")...anyway, on ar15.com there is more than enough evidence that I was easily convinced not to buy any Hornady Frontier. I don't care if it was loaded at Lake City when Federal was operating it, and I don't care if the rounds in question were nominally/substantially similar to XM193...there are too many people posting too many similar over pressure signs and literal kabooms to ever put Frontier into any of my firearms. And it's not just 55gr it's also the heavier match bullets for multiple people as well. Sure, there are also plenty of people with no problems in a case or three...just as there are a plethora of people out there with that many rounds through their 'as good as' rifle with zero reported problems. Don't care.

Avoid Frontier ammo

Certainly, do not shoot Frontier or buy any. There are plenty of good alternatives (or will be once the current ammo drought is over).

But don't confuse an echo chamber of #me2s jumping on the bandwagon with a meaningful sample size. More importantly, don't continue to shoot any ammunition that pops primers or shows other signs of extreme overpressure in your firearm.

I reload and not one of the Frontier cases I fired showed high pressure signs. I am pretty sure there was at least one "hot" lot of the Frontier ammo and apparently I luckily didn't have any of that lot.

Andy

[robbins290]

The "bolt life" will still out last the barrel life. Even in a carbine gas system (if within spec)

When/if you get to a spot where your barrel is spent. Replace the bolt to.

[Joe Mamma]

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"?

There was a long and detailed discussion about bolt life in the following thread from last year. You may have missed it. lysander posted some really good data (which I assume is true) in that thread.

I posted in my thoughts in that thread. There are lots of different perspectives on the issue.

"When is a bolt "old"?"
https://www.m4carbine.net/showthread...-quot-old-quot

Hope this helps.

Joe Mamma