AO Precision True Mil-Spec SP/HPT/MPI 5.56 Bolt Carrier Group - BCG556
In stock
Right here is a True Mil-Spec BCG. Each and every bolt, test fired from the factory. This unit is for builders who prefer tried and true manufacturing and aggressive quality assurance testing over fancy coatings, proprietary profiles and laser engraved logos. AO Precision has provided BCGs to large military contractors such as FN America and large commercial retailers who re-brand and sell these at a considerable mark-up. You can now get these directly from AR15Discounts.com and save big!
Bolt
- Machined from Carpenter Technology No. 158 alloy.
- Heat treated
- Shot peened per ASTM B851/SAE AMS2430S
- Individually High Pressure Tested (test fired)
- HP proof testing, 100% using a high pressure M197 or SAAMI commercial equivalent, without evidence of failure
- Individually Magnetic Particle Inspected after Initial Test Fire
- Manganese Phosphate Finish
Extractor
- 4140 Steel per ASTM A108, cold drawn and stress relieved BHN 187-22
- Manganese Phosphate Finish
- Extractor Spring
- Black Extractor Insert
- Viton O-Ring
Carrier
- Machined from AISI 8620 aircraft quality alloy per ASTM A108/A322-13
- Full Mass M16 Profile
- Stress Relieved
- Hard Chrome Bore
Gas Key
- Machined from 4130 chromoly steel alloy per ASTM A108/A322-13
- Grade 8 Hardware
- Properly Staked
- Hard Chrome Internal
- Permatex sealed
| Weight | 11.52 oz |
|---|---|
| Bolt Material | Carpenter 158 Steel |
| Cartridge Compatibility | .223/5.56 NATO/.300 BLK |
| Finish | Mag Phosphate |
| Carrier Profile | M16 |
| High Pressure Tested | HP Tested |
| Magnetic Particle Inspected | Magnetic Partical Inspected |
| Platform | AR-15 |
| Bolt Finish | Mag Phosphate |
| MPN | BCG556 |
| UPC | 999994494 |
Compliance
NFA (National Firearms Act) compliance is crucial for legal ownership and transfer of regulated firearms and accessories like short-barreled rifles, suppressors, and certain types of ammunition, ensuring adherence to federal regulations to avoid legal penalties and ensure responsible firearm ownership.
Customer Reviews
- Reviews
- Questions
- price
- quality
- bolt
- rounds
- issues
- shipping
- finish
- build
- parts
- barrel
US
BCG Mil-Spec
Perfect fit and appearance in my Retro A-2 build.
USGreat Price
Works flawlessly, Great Price
USPhosphate milspec the way to go
I currently own 5 bcgs, 3 are Microbest phosphate CL, 1 PSA premium phosphate CL from 2013, 1 Bushmaster phosphate CL from 2006. All have performed flawlessly, 2 older bcgs have approximately 4300 and 3700 rds. The PSA has the chrome overspray iconic to Microbest, the Bushmaster chrome is a little less prominent, maybe Toolcraft or AO precision? Got 2 AO precision bcgs at the same time, 1 has some faint vertical tool lines only on the tail sides of the carrier, not a concern for me in that area, the other is overall smooth. Good machining of the rails on top and also the tongue underneath. Phosphate finish is even all over. Both chrome interior bores are very smooth and shiny. Both bolts marked HPT/MPI and fit tight to the bore. Cam pin has no wobble. Straight cotter pins. Extractor and ejector pins recessed evenly. Staking is more robust than Microbest on the gas key, not triangular shaped but almost half-moon, looks like how Centurion does theirs. Extractor spring has the donut, will change out to a 5-coil Sprinco and delete that. Very happy with the initial inspection, was hesitant to buy these since Microbest has been so reliable. Sales price/discount code was too good not to try. Will range test this weekend.
USSold on phosphate.
My first BCG was a Nickel-Boron coated one, which I've more of less stuck to since. I had always been told it's the latest and greatest, and, honestly, since where I live it is winter for over half the year, it seemed sensible. (You can run nickel boron dry, and not have to worry about how the weather/cold affects lubricant.) I was told I should give the standard phosphate and chrome BCG a try. I have yet to try it in the winter, but I can tell you I've been very pleased with its performance so far during the summer months. Why? Sometimes I go on range trips with "high volume" shooters and putting several hundred rounds through a platform is not unheard of, and it also means buying lots of cheap ammo. Some of this cheap ammo can foul up the action in 200-300 rounds - I saw fouled up, but one of my Nickel Boron bcg will have shed any lubricant I've put on it, and the carbon buildup would start to hinder functions. The last range trip, I put 500 rounds through my platform, and the BCG still had lube, and was functioning flawlessly. Winter will be the ultimate test, but I think I'm converted to the old ways.
USGood price on an AO Precision BCG
Good price works great so far,
