I've always immediately replaced my bolts when I see the first sign of a crack (always at the cam pin hole).

Do you immediately replace the bolt or monitor the crack?

One bolt cracked on both sides before I noticed (I almost never disassemble my BCG until the round count is high).

My "cleaning regimen" for range guns consists of running a patch thru the bore and adding BCG lube every 1000rds.

With the current low cost of bolts, why not replace?  Not worth the risk.

JUNK IT.

Thanks guys - that's what I've done so far.  I'll just keep trashing them when I see the first crack.

What's the round count when the bolts crack? Manufacturer?

Once you find a crack, what exactly are you monitoring for, the impending Kaboom? Replace it now.

The round count depends on a couple of factors: how hard / hot the gun is ran and the type of ammo.

I start looking at the bolt at 5k if the gun has a lot of full house (NATO spec 556) use.  Inspection interval = 1000rds starting at 5000.
I start looking at the bolt at 7k if the gun sees Wolf only use. Inspection interval = 1000rds starting at 7000.

I only use BCM, Colt and DD bolts.

The double cracked bolt (only time I've seen this happen...opposite sides of the cam pin hole) was an ArmaLite bolt (this was a long time ago).

This ^^^^^ is just my method.  I have no idea what proper PMCS would be.

Again, I always replace bolts when I see a crack. I was asking because a guy I shoot with noticed a crack and said he's just going to monitor it .  The gun has an overgassed Spike's midlength upper.  I told him to spend $65 and save his upper.  We're shooting tomorrow night and I wanted to know if I should stay clear of him...because he didn't listen.

ETA: I don't want to be in the debris field if he KBs.

I was being rhetorical. I didn't mean to sound like I was accusing you. I should have prefaced with "My response would be..."

I check every time I clean a weapon.
Sooner or later your buddy is going to find out why that is a deadline issue.

I would replace it immediately.  With ~30 AR's, I haven't shot a bolt out yet.  I have worn a few ejectors and extractors out.

No worries - we're all good!

30 rifles is a lot of units to spread wear around!  That's awesome.

Well, a crack at the cam pin hole won't be a too big of a danger to others when it fails.  The tail end will break off and probably mess up some parts of the gun, but the lugs should remain locked when they need to. (yes, he should just replace it.)

A cracked lug, however, is a more risky proposition.  Although, I do know of several instances where a bolt with a known cracked lug has gone 3,600 rounds of M855 without complete failure.  I would use this information as "I know I am safe if a bolt lug cracks while I am at the range," as opposed to "well, it cracked, we can go another 3000 rounds before replacing it..."

EDIT: Also, this should be a good lesson in why you should field strip, clean and inspect after every shooting session....

IMHO replace immediately unless you want a failure to fire/extract.  Bolts are too in expensive nowadays and even if they weren't a cracked bolt discovered during PMCS is immediate replacement period.

Why is this even being discussed? Down that bolt and replace.

Problem solve. Problem staying solved.

What's the big deal, 60 thousand PSI isn't anything to worry about when it is no longer controlled.

I rest my peace

We are all on the same page.  

My shooting buddy, on the other hand, said he's going to "monitor" it.

I need to find a new shooting buddy, because it'll be my job to fix his POS rifle when it comes apart.  I'm in the process of working out how he managed to make a Glock 19 a single shot

You're shooting buddy is an idiot. It's like "monitoring," when you have low brake fluid or a leaking brake line. Or "monitoring" a stab wound to the chest. The guy has no business being around firearms. He's a moron.

This on a single rifle?

Somethings wrong if you're going through bolts that frequently.

Several different rifles over the years.

I shoot about 1,000rds a month (2 trips a week at 120rds a trip is my standard schedule...but sometimes life happens and I miss a trip.  Sometimes I'll shoot over 1000 in one weekend).

He's cheap.  Plain and simple.

I try and to avoid taking him.  A couple of trips ago he "forgot to bring ammo"....

Was posting from my phone..siting on the toilet before work

Regarding shooting schedules:

I try to shoot about 1000rds a month.  There are a lot of factors that impact my ability to maintain a normal shooting schedule (work, family, work, weather, work, did I mention work?).  I probably shoot between 7-10,000rds of Wolf 223 a year.  My best laid plans...are to visit the range twice a week, every week, with four 30rd mags fired each trip.  This totals nearly 12,000rds a year but life simply happens.  If I miss a week (or two) I may shoot over 1000rds in a given weekend.

Regarding bolt replacement:

I never have more than a couple of lowers at one time, but usually have several uppers. I have a tendency to change out guns and/or uppers a lot.  I'll often buy three or four difference configurations and will only test them. For example, when I went through my "piston AR phase" I had about 20 guns / uppers pass through my hands over a period of about two-three years.   Some of these were sold unfired, and some were only tested (couple hundred rounds).  A few saw extensive use.  Regardless, this situation kept the overall round count down over the aggregate.

Occasionally, I get infatuated with an upper and it'll see extensive use.  For example, I'm a big fan of the Colt 6920.  I've owned several.  I've had some with a lot of rounds through them.  A friend is a Class 3 FFL that also sells non-NFA "black rifles" (he wont' even transfer FUDD guns).  When its time for me to pass along a heavily used upper (or complete AR) I just tell him what I want out of it (for example: $500 for a 6920) and he puts it on his gun show table.  Whatever he makes over my amount is his to keep.  I always give him a print out to include with the rifle detailing the gun's use and maintenance (e.g. Bought used online; 5,000rds of Wolf; no classes / no abuse; changed buffer to carbine weight; heavy bolt carrier lube added regularly; bore patched every 1000rds).  When I want to sell a gun or upper that I either didn't use at all or only tested a few rounds through I always use the internet.

Most of the AR15 related failures I've experienced happened when I owned "lower tier parts and/or guns".  I've always had a "good" rifle in reserve (like a 6920 or BCM) but I use to buy "bargain" guns to run hard at the range or in classes.  This meant I've had a bunch of ArmaLite, Bushmaster, DPMS, Eagle Arms, Rock River and Smith & Wesson guns.  WAY back in the 80's and 90's I even had an occasional Olympic Arms .  Most recently I experimented with PSA products, but they had issues of their own. I've found you get what you pay for so I only own / buy / use "quality" ARs and parts now.  My personal definition of "quality" includes: BCM, Colt, and Daniel Defense.

I can't quantify how many rounds it takes to crack a BCM or Colt bolt because the only units I've cracked came from guns that I bought used.  I've not ran enough rounds through a DD to see a parts failure. I keep a range record for all guns / uppers I buy new.  I'll post when I see a cracked BCM or Colt bolt from an upper or full AR I bought new.  However, this could take a while because I'm currently spreading my training out among (4) BCM uppers, (2) Colt uppers and (1) DD upper.  That's 7 uppers in rotation....which means they will only see about 1,000-2000rds a year each.  Again, as previously mentioned I also tend to switch out uppers regularly.  I would like, however, to run a single "newly purchased by me" 6920 upper until it failed (to satisfy my curiosity).

Regarding cheap-azz "friends"

I made a mistake of selling an expensive gun (with an ACOG mounted) to a long time acquaintance.   The mistake I made was agreeing to him paying me "on time". I understood this to mean I was going to get paid in full within a couple of months.  It has now been six months and he's still not completed paid up.  This means I feel obligated to take him to the range when he asks.  When I FINALLY get the balance of my cash - his free rides to the range will cease.  We probably all know a "mooch".  Some are worse than others, and I managed to deal with a terrible one.  However, because of secondary relationships that I value...I have to stay in this deal until its done (i.e. I don't want to damage shared relationships with long term FRIENDS and FAMILY).  The cracked Spikes bolt is a separate and unrelated issue (to the money owed me), but it shows this individual's character.  I should have known I was in trouble when I had several related people contact me in shock that he bought a quality AR with an ACOG on it.  They all related what a penny-thrift he was (but it was too late...the deal was agreed to and the gun was in his possession).

In regards to your "cheap azz friends". A cheap friend wants to divide up the restaurant bill to the penny and he orders water and the cheapest thing on the menu and leaves a 5% tip. An asshole borrows money and never pays it back. Whether it is borrowing cash from you or not paying for something he "bought" from you it is the same thing, an asshole deadbeat.

I learned long ago never to loan money to a friend.

I have more recently been eliminating so called friends who are really just users. You know the friend who calls you pal, buddy, mate or some other condescending name and asks for a favor. Once you do the favor you never hear from them until they need the next favor. They usually make a little bit of small talk but really only do that to suck you in. I have cut ties with these types of friends who never do anything for you but always call for "favors".

Lastly I have also been cutting ties with the "drive time" friends. These are the ones who call you when they are driving home from work or are driving by themselves. Then they usually in mid conversation declare "I am home now. Talk to you soon." They never want to talk except when they are driving. I am their entertainment for the commute but not good enough to talk to when they are home. Their time is more valuable than mine apparently.

I have reduced my friends to about 4 guys. The rest are considered "guys I know". The users have been eliminated and I don't deal with them. The 'only call when they are bored in the car friends" have been reduced to laeving me voicemails and I will email them.

Bottom line....pick real friends and keep them. Let the rest go. Your life will be better for it.

Tell the asshole who owes you money you expect him to have it in 30 days or he can give you the gun back.

This. That this is even a consideration is mind numbing.

Ah... well ask him how much his copays for the emergency room visit and a prosthetic hand will cost.

No gun has ever exploded from a bolt lug breaking

Unless he posted something later, the first few imply a crack at the cam pin hole. Now what happens if the bolt gives way there? What stops the carrier?
Oh, fine, not a hand. A big fucking hole in his shoulder.

 Lol, no.

Just a locked up gun that's a bear to disassemble.

The carrier key . . .

Have you ever tried to remove a bolt carrier without removing the charging handle?

Sans a key the buffer, spring and receiver extension.

Think about that for a minute. A 5.5lb action spring and 4.4oz buffer are enough to slow the carrier down so that it barely strikes the end of the buffer tube.

Even if it didn't have a buffer tube, action spring, buffer, or carrier key it won't blow a hole in your shoulder.

The BCG doesn't move that fast.

Approx 3100rnds, most full tilt 5.56 loads.  BCM.

It's dead Jim, dead.   Attached File

"Khaaannnn!" 3100rds is very premature.  

Was this suppressed? That crack is a lot worse than I'm use to seeing (I'm use to seeing them inside the cam pin hole). You may want to send that one back to BCM for eval.