[RDShoots]

If I was to buy an "off the rack" AR like a Ruger or S&W, what kind or life (how many rounds) should the bcg last?
If I was to buy a replacement bcg, is there a "go-to" standard that I should be looking at?

I know this is the AR forum but would an AK47 have these same standards, again, if I was buying an American made AK "off the shelf" type?

Thanks for the help,

 

[zant]

AR------5-7k on bolt before I would replace it.I've broke 2 with over 7k--replaced with 9310 bolts
AK-don't know but the trunnions go south at about 100k rds,thats from records kept by places that rent MGs

 

[RDShoots]

AR------5-7k on bolt before I would replace it.I've broke 2 with over 7k--replaced with 9310 bolts
AK-don't know but the trunnions go south at about 100k rds,thats from records kept by places that rent MGs

Thanks Zant - picked up a couple just in case...

 

[zant]

From research and talking to armorers---HPT seems to be a problem with bolt lugs breaking---experts are about 50/50 whether high pressure testing is good for bolts.Some say it weakens them,others say no---I lost an FN locking lug on a PSA with a ton of rounds and abuse..........The other bolt broke at the cam pin hole-which seems to be the rule with less expensive bolts....I returned the broken bolt with locking lug and asked them to see if they knew why it broke.Did;nt ask nor expect a replacement and made that clear.Just wanted info.He said it was just worn out.So I bought a 6pack of 9310 bolts,should be all set.

 

[Stites]

I'd say as long as you maintain your platform well, you should get several years out of a BCG so long as it's mil-spec or better. I ran the same M203 for eight years, including one in the sandbox - never had an issue. Recently built my own and went with a Toolcraft DLC-coated BCG with a 9310 bolt. It's better than mil-spec, so I got high expectations for it.

Something else to consider is your upper - is it made from 6061 alloy, or 7075? 6061 is about the same strength as mild steel, but with a greater tendency to gall and thus wear out sooner. 7075 is aircraft alloy, which is mil-spec and has a yield strength greater than the tensile strength of mild steel. It's the one you want, and typically you'll pay more for it. But then you'll certainly get what you pay for, too.

 

[PRR1957]

A friend of mine used to be part owner of a AR15/10 company that sold uppers and various AR parts. His company was the first to offer bolts for 7.63x39 made from 9310. Later he had all his AR bolts made ftom 9310.

As for bolt life. Any high quality AR bolt should outlast the barrel.

Just a FYI. The BCG is a abbreviation of Bolt Carrier Group, which is the bolt and the bolt carrier assembled together. The exception is if it’s a 9mm Colt AR which it’s just called a bolt.

 

[jbmid1]

Chrome is the gold standard for the bcg, right?

 

[PRR1957]

Chrome is the gold standard for the bcg, right?

No. Gold colored titanium nitride is the gold standard.

Actually Nickel Boron is so far the best coating on a bolt carrier in that it has an inherent high lubricity, corrosion resistance, and very durable with a Rockwell hardness between 52-56.

As for the bolt. Manganese Phosphate coating is still used for most AR bolts. There are some hard chrome bolts, but the opinion is that the chrome is microscopically abrasive which can ware the barrel extension bolt lug abutments.

 

[zant]

Have a couple NickelBoron coated-over 5k rounds and they look new-carbon wipes right off.

 

[jbmid1]

The Mattel toy has come a long ways.

 

[Stites]

An 8620-alloy bolt carrier and a Carpenter 158 bolt with a manganese phosphate coating is mil-spec. That 8620 alloy is used to make ring/pinion gears for automotive drive axles. Stout stuff. Carpenter 158 is stouter still. So mil-spec sets the bar pretty high to begin with.

Bolts made from 9310 alloy are a bit stronger than ones from Carpenter 158. 9310 is used in the production of automotive transmission gears, so it has to be able to withstand that high shock load from when Jimbob dumps the clutch in his notchback 5.0 Mustang and roasts the tires a full six feet before the motor blows a head gasket. 😁

As for coatings/finishes, a nitride/QPQ finish creates a harder, slicker surface that doesn't flake off. The nickel boron coating is harder and slicker still. DLC, or Diamond-Like Carbon, is supposed to be the hardest and slickest of coatings, but not by much. There are other coatings and finishes as well, but they're either too gucci for me to remember or way out of my league to afford.

In reality, it's all splitting hairs once you get above the black nitride/QPQ finish. Only reason I settled on the DLC-coated BCG was because I found one on sale for the same price as a QPQ-finished one. Maybe even a little less?

 

[RMC51]

One way to fix your BCG problems:
Get a Spikes Tactical BCG, they are Lifetime warranty, I have seen Spikes replace gas rings, ejectors and even a firing pin on a very heavy used 6.8 hog shooter.
Primary Arms has them in stock for $135.

If you have an extra one on hand and you have a rare failure, pop in the spare and contact Spikes they will fix it.
Sometimes you can find them on sale for $120-$125.

or if you want nickel, Primary Arms has them in stock for $202

 

[ITSZHC13]

I have an S&W M&P15 with ~2500-3000 rounds through it so it should be good for at least that much