Sooo I've been out of the ar10 game for a while.

I have a new gen 2 GAP-10 and they tell me I have a Armalite BCG in my rifle. I thought the Armalites weren't compatible with PMAG's (I could be wrong), so I call Seekins (who makes GAP's receivers) and they tell me I have a DPMS style BCG.

So now I'm confused as to what I have or what will work. The BCG I do have in my rifle is parkerized and I want a DLC type Bolt Carrier in there.

I want to slap a Cryptic Coatings BC in there with my existing bolt but I can't figure out if it will actually work. Cryptic says theirs are DPMS style.

So 2 questions:

Will a Cryptic BC work in my rifle?

What is the interchangeability of BCG's in Armalite vs DPMS platform?

For sake of simplicity can we totally exclude the new DPMS Gen 2 from this thread?

Is your firing pin spring retained to the rear when captivated by the FPRP?

If you have an ArmaLite, it will be easy to tell.

They have an excellent design, the one I like the most.

There are dozens of different AR10 BCG designs:

Original tool room ArmaLite from 1955-1959, hard chromed

Dutch ArmaLite production rifle carriers, hard chromed

Dutch ArmaLite LMG carriers with cam groove for feed mechanism, hard chromed

ArmaLite-Colt AR10A small frame carrier, 1959 hard chromed

KAC SR25 carrier 1990, large body with AR10 dim rails, AR15 diameter tail for compatibility with AR15 RETs, hard chromed

Eagle Arms/ArmaLite Inc. carrier with sprung firing pin to reduce slam-fire likelihood

DPMS LR-308 carrier (patterned off the SR25 carrier) hard chromed

DPMS AP4 carrier, parkerized

JP Low-mass carrier

LMT MWS carrier, hard chromed

LaRue OBR carrier, hard chromed

KAC M110 carrier, with FA serrations

KAC SR25 EC carrier with sand cuts on the guide rails, no FA serrations

ArmaLite Inc. AR10A with FA serrations

Colt 901 small frame, AR10 diameter carrier, shorter than SR25 carrier

DPMS GII carrier, AR15 diameter, with FA serrations

Aero aftermarket carrier without serrations

Aero carrier with serrations

A bunch of other aftermarket carriers with differing guide rail lengths, who knows what vent port locations and diameters, who knows what bolt bore dims, cam pin helix, etc.  too hard of steel carrier keys, guesswork dimensions, metallurgy, and fitment

I think it is. Pretty sure it was not floating when I shook it around in my hand. I'll check when I get off tonight. Work a ton.

This is it. Yes it's held to the back.

My Armalite AR10 .308 B-Model's firing pin looks like that one in the pic with the spring.

That would be an Armalite AR10 BCG.

Thanks guys. Since no one makes these I'll just get it coated.

Ranier Arms sells some gold ones if yer lookin' for bling.

But seriously, I have read on here that you match the Armalite bolt to the Armalite barrel extension and the carrier can be Armalite or DPMS. 

Need someone with more experience to let you know for sure.

What are you planning on coating and why?

The bore for the bolt is already hard chromed, with some very critical dimensions that determine the reliability and function of the rifle.

Hard chromed bolts were shown to cause hydrogen embrittlement and early fatigue, stress risers, and cracking on the first production AR15s, which is why the Army and USAF dropped that coating from the TDP early on in the 1960s.

Less of an issue on an AR10 since there is so much mass and lug strength, as well as cam pin hole wall thickness on an AR10 bolt, but the carrier getting coated raises a number of questions for me.

I am going to coat the whole BC and complete bolt. I don't like the grittyness of phosphate. It's like sand paper to me and has a greater drag coefficient than if the metal was just polished with no coating at all. Another reason is if I have a round chambered, it takes a pretty good yank to get it out. I assume because I have a match chamber, which is fine, but if a slicker BCG helps even a little bit, I'm happy. Also this rifle is only shot suppressed, so the odds of a malfunction due to fowling of the action are greater. NiB has less odds of a malfunction if I'm shooting a match. Cleaning is super easy too.

Dimensionally speaking, you bring up a great point. The current coating vs nib will be less than a couple thou of each other. After a bunch of research I am having WMD do the coating (they are firing their "coating of customers parts" business back up). I asked them about the bore of the BC was told that NiB there is better than hard chrome and NiB is 30% stronger. With that said, I have a complete WMD BCG in my precision .223 AR and it's purely perfect. Sadly I do not know if my freaking Bartlein 6.5C or 6.5G will out shoot it. Still working on that part

I do need your wisdom on something else related. I noticed the back end of the rails on the BC are kissing the lower receiver. What do you think about me putting a small taper/ramp there before I have it coated? Would that create tilt? Or am I thinking correctly that it would help alleviate that intersection and be a smoother transition of the BC lower rails into the buffer tube? You can already see there is some wear there only after 60ish rounds.

I went ahead and did it. Just chamfered the edges then polished it with a polishing wheel. Yall let me know how bad I ruined it

BEFORE





AFTER





I put a slight touch on the top rails too.


The destruction tools:)

i think, imho, contact between the BC and the lower receiver, as you show, is indicative of an issue perhaps with buffer length (just a tad bit short), or buffer spring (just a little too soft), resulting perhaps in the buffer bumper being squished too hard?  i don't think you should have contact at that spot.

A quarter or two at the bottom of the buffer tube would probably have solved that problem.

This is the answer, and it's cheap.