Recent Army M16/M4 bolt issues

[Slater]

Hard to believe that some troops are actually lubing ammo (if this is indeed accurate):

"Soldiers, word from the field is that some of you are reporting M16 and M4 bolt damage. The bolt locking lugs are cracking, breaking off, causing weapon stoppages, and creating a risk of injury and weapon damage.

There are warnings in every weapon technical manual (TM) telling you to keep your ammo clean and dry. Don’t be fooled by the incorrect field-expedient guidance that says a little lube in your chamber and on your ammo helps the weapon perform better!"


https://www.psmagazine.army.mil/News...clean-and-dry/

[ndmiller]

I've always inspected the bolts after every few shooting sessions when cleaning, but haven't really seen any issues to even know what I was looking for. I also didn't know about the way to see hairline cracks quoted below from the article, so may have been missing them all along. Is this widespread knowledge I just missed or a nugget of military SOP?

Will try this before going out again, I've got bolts with 5-20K rounds and not even sure when failure is likely to happen.

Also, look for hairline cracks at the base of each bolt lug. An easy way to see the hairline cracks is to follow these steps.

Put a drop of CLP at the base of the lug.

Then try to wiggle the locking lug while watching the lube.

The oil will seep into the hairline crack and make the crack easier to see

[chamber143]

I've always inspected the bolts after every few shooting sessions when cleaning, but haven't really seen any issues to even know what I was looking for. I also didn't know about the way to see hairline cracks quoted below from the article, so may have been missing them all along. Is this widespread knowledge I just missed or a nugget of military SOP?

Will try this before going out again, I've got bolts with 5-20K rounds and not even sure when failure is likely to happen.

Me as well. I have a few with well over 7-8k and they seem fine. I have heard that the nominal bolt life is somewhere around 3k. Then again who knows. I know the military isn’t replacing bolts at 3k.

[ndmiller]

I have heard that the nominal bolt life is somewhere around 3k. Then again who knows. I know the military isn’t replacing bolts at 3k.

Ughh, seriously 3K, I've never replaced a bolt, ever, so probably missing something with 15K on some of mine. I really tried to learn about the AR over the years, but seems like all these important nuggets keep surprising me. If anyone has a good book on the AR which includes preventative maintenance showing critical component life/failure maybe with pictures please post it. I see a few all encompassing history of the AR books reviewed here and photocopied manuals at gun shows, but have to figure there is a great AR book for this sort of thing.

I'll grab a spare bolt or two just in case the CLP shows I never saw the cracks....But is 3K the real answer when warning signs start showing up?

[sinister]

The USAMU usually changes out M16/M4 bolts on the third barrel change -- somewhere around 9,000 - 12,000 rounds. Impending failure is usually marked by cracked bolt lugs.

Same with hammer springs.

[okie]

This reeks of complete BS. First off, lubing ammo wouldn't do anything but make whatever situation they think they have worse. If it's some misguided attempt to extend bolt life then it would have the opposite effect by making the rounds stick in the chamber harder.

Second, M16 bolts last pretty much forever. M4 and especially Mk18 bolts can be pretty consumable depending on rate of fire, but as long as there's not a bunch of full auto going on they should last a long time. That Henderson place was getting tens of thousands of rounds out of M4 bolts doing nothing BUT full auto.

[Circle_10]

The USAMU usually changes out M16/M4 bolts on the third barrel change -- somewhere around 9,000 - 12,000 rounds. Impending failure is usually marked by cracked bolt lugs.

Same with hammer springs.

So you can generally get away with pairing an existing bolt with say, 9k or less on it with a new barrel? I was never clear at what point the bolt should be replaced as well when changing a barrel.
Even if a new bolt is prudent any time you change the barrel it’s good to know one could theoretically get away with using an existing, relatively broken-in bolt with a new barrel. Though I’d assume checking headspace would be advisable.

[vicious_cb]

Lets introduce incompressible liquids into the chamber thus increasing pressure then complain about bolts failing. Army logic. f***ing retards.

[okie]

Lets introduce incompressible liquids into the chamber thus increasing pressure then complain about bolts failing. Army logic. f***ing retards.

It's not just the Army. There's a cop on arfcom who claims AR carriers shouldn't be lubed, and he will absolutely lose his shit on anyone who tries to point out the errors in his logic.

[kirkland]

The USAMU usually changes out M16/M4 bolts on the third barrel change -- somewhere around 9,000 - 12,000 rounds. Impending failure is usually marked by cracked bolt lugs.

Same with hammer springs.

I thought barrels lasted a lot longer than that. Or is it because of high rate of fire? I'm still trying to shoot out my barrel, no luck so far, it's around 10k-11k