"Oh No! I bought a BM/RRA/Stag before I knew better!"

[rmecapn]

5) Buy a properly tested, staked, constructed bolt carrier group (BCG) with the proper extractor insert. The bolt itself should be Magnetic Particle Inspected (MPI), Shot Peened, and Proof Fired. You can buy a top quality BCG from Bravo Company, G&R Tactical or LMT for around $130. You can either change out to this BCG right away, or use the one that came with your rifle until it breaks and then switch it out. The choice is yours.

Just curious, how does one tell if their bolt has been MPI'd?

[carbinero]

If you already have a fairly new, chrome-lined, well staked CMT or "less than top tier" carrier, why not just get a $60 bolt from BCM and save $70? Are the BCM carriers that much better?

[Robb Jensen]

Just curious, how does one tell if their bolt has been MPI'd?

Typically their engraved or stamped with MP.

[C4IGrant]

Just curious, how does one tell if their bolt has been MPI'd?

Some companies like BCM, Colt and LMT mark them. Other companies like Sabre Defense and Stag (CMT) do MP test, but do not mark them.


C4

[C4IGrant]

If you already have a fairly new, chrome-lined, well staked CMT or "less than top tier" carrier, why not just get a $60 bolt from BCM and save $70? Are the BCM carriers that much better?

The gas keys on the BCM's are better. Since you already have a bolt carrier, I wouldn't worry about it.


C4

[rmecapn]

Some companies like BCM, Colt and LMT mark them. Other companies like Sabre Defense and Stag (CMT) do MP test, but do not mark them.

Apparently, CMT only batch tests. This is the reply I received from them concerning the marking of their MP tested bolts:

"MPI is done on sample lots only, if there is no marking on it to indicate that the testing was done than it was probably not done on your piece. We have had no problem reports with regard to cracks, and so same lot testing continues."

[Shihan]

I always need More Help!!!

I think you're 3/8th" group is outstanding with an AR and 12X. I just can't see that closely anymore without at least 16X.

My personal best is .337" (holes measured center to center) with a Remington VS, Timney trigger and a 14X scope. This was in 1998, and I still have the target. The 32X scopes I was referring to were being used by guys who could "Regularly shoot" 5 shots under .2 MOA with Custom BR Guns, usually in 6 PPC caliber. And yes that means 5 shots in ~2/10ths of an inch at 100 yds. The world record is under .1 MOA.

Tack

I find that being overpowered with the optic screws up my groups.

[C4IGrant]

Apparently, CMT only batch tests. This is the reply I received from them concerning the marking of their MP tested bolts:

"MPI is done on sample lots only, if there is no marking on it to indicate that the testing was done than it was probably not done on your piece. We have had no problem reports with regard to cracks, and so same lot testing continues."

Hmm, that is odd as just last year, they said that they were MP testing all of them.

C4

[rmecapn]

Hmm, that is odd as just last year, they said that they were MP testing all of them.

C4

I don't know, Grant. This is the question I posed to them in my email:
"I was wondering if you could tell me if you magnetic particle test your AR-15 bolts? If so, do you mark those bolts as being MP tested in any way?"

And the reply above is what was returned. It is my understanding that batch testing is sufficient to meet the requirements of the TDP. However, if they told you they were testing each individual bolt, then I'd say you were definitely mislead (intentionally or not). Is this similar to the issue that S&W had with them?

[carbinero]

I just received a back-up bolt from BCM. I'm not messing around with "I thought" on this part; the original will ride the bench.

Note: received by US Mail in a beat up express box with a split large enough for a bolt to squeeze through. Bolt in sealed heavy duty clear plastic bag: not the worse for wear. Bolt assumed 100% GTG.