Bolt failures

[cz7]

ok the gas system hole in the barrel is at a point where psi is higher then a 20'' barrel and steel alloying maybe a part too... bolt hole were cam bolt slot angle needs to be reworked too

[Dragon 2 Zero]

lol! That last bolt - the one that's cracked-but-not-broken-apart ... that one is mine! It's a Bushmaster with just a few thousand rounds on it - about 3000, IIRC. The weapon had turned into a single shot carbine. I took the thing apart on the range and found that crack. I had a spare with me. Swapped it out and carried on.

Ya know what else I have noticed on my Carbine? ...(get ready for a Master Of The Obvious type statement...) The firing pin retaining pin gets positively Beat To Shit when I run Green Tips through it. I hate it when that happens...

[mike240]

Has any work been done to determine what is the shortest barrel that can be run with a mid length gas system? Would this reduce the some of the problem?

[AMMOTECH]

lol! That last bolt - the one that's cracked-but-not-broken-apart ... that one is mine!

Thanks for the picture!
It's a good reminder for everyone to check all their components when they clean their rifle and clean/inspect it after every trip to the range.
Just think of what the picture would have been of if you did not replace that bolt...

[Low Drag]

A buddy sent me a pdf from a firm that is trying to sell the round counters to the military. They state that bolts fail on Gubmint issued M4s between 3K to 6K rounds under harsh conditions. 6K to 10K on "milder" schedules. Barrels burn out at about the same time.

I've heard all the stories about Bushmaster and "others" failing, but it looks like all M4 type carbines have this problem. I wonder if the size of the gas ports could be changed to decrease the pressure? I've added a heavy buffer but that does not address the pressure coming down the gas tube and the resulting pressure placed on the parts in the BCG.

[jmart]

I wonder if the size of the gas ports could be changed to decrease the pressure? I've added a heavy buffer but that does not address the pressure coming down the gas tube and the resulting pressure placed on the parts in the BCG.

I've wondered the same, but I suspect if you went much smaller, you'd probbaly run into relaibility issues with weak ammo or when running in the cold.

While adding weight doesn't reduce the pressure it does keep things locked up so you avoid the situation of moving parts while pressures are still way high. Given that extra amount of time, it has to make life easier on the parts.

I also wonder if there's any correlation to running the gun dry vs having it adequately lubed. Again, I suspect that if the weapon is properly lubed, parts life will increase.

[C4IGrant]

Has any work been done to determine what is the shortest barrel that can be run with a mid length gas system? Would this reduce the some of the problem?

14.5 I believe.


C4

[C4IGrant]

USMC03, I thik you are correct! The ARMS SIR DID break that bolt!




C4

[SinnFéinM1911]

USMC03, I thik you are correct! The ARMS SIR DID break that bolt!




C4

Without a Doubt !~

[Seth Harness]

The pressure behind a bullet in a 20" barrel is greater than the pressure behind a bullet in a 16" barrel... correct?