I have used a number of AR-15 bolt carrier groups over the years. You can tell which ones are engineered well and which ones are not by just dry fire charging the AR-15. Some have some drag to them. You can tell they they are low speed high drag. While others, like the JP Enterprises FMOS I have, feel like glass. This is particularly interesting when lubricating them with the same lube! This Fathom Arms Enhanced Bolt Carrier Group feels like what KY Jelly feels like between your finger (among other things). I could compare it to a Slip and Slide. It is very smooth. The only other AR-15 BCG to date that compares is the JP Enterprises FMOS I have. It uses a Black Nitride finish, which is a top of the line finish. It is better than, for instance, chrome and nickel plating with increased wear-resistance, fatigue strength, corrosion resistance and lubricity. Fathom Arms CNC machines the entire external surface, including the bolt bearing surfaces after heat treatment to ensure proper and unaltered tolerances. This is they way to make a AR-15 bolt carrier group.
I have over a thousand rounds through my Fathom Arms Enhanced Bolt Carrier Group in my Budget Jack Carbine. I could put more rounds through it but I have some classes lined up with my other AR-15 (Battle Blaster rifle) and wanted to get my thoughts out there instead of sitting on the review for more time. During this time I have used Lucas Extreme Gun Oil on the BCG and cleaned it after each range session. I like to do that the first few range trips as things are "breaking in". I have shot 55gr FMJ, M855, 77gr OTM Black Hills, 75gr BTHP Ultramax, Barnes 55gr and a few others. I actually took a box of left over ammo which was a mix of 12 different ammo's and ran it one afternoon. I have had zero malfunctions. This Fathom Arms Enhanced Bolt Carrier Group just eats up the ammo and spits it out. I visually inspect my gear each time I clean it, nothing like cracks have happened. Running this Fathom Arms Enhanced Bolt Carrier Group with a H1 buffer, enhanced buffer spring and mid length gas system really worked well for me.
The gas key is properly staked. I saw no backing out, as you shouldn't in the first place but just passing along the info. Easy to clean, even though that is never something that is high on my list. Maybe it is on yours. They put time into making their BCG's, use great materials, make them to true MIL-SPEC and high pressure and magnetic partical test each lot. The one thing they market these BCG's to do is have reduced cant/tilt during recoil due to their relocating key bearing surfaces. I can say this BCG feels different, it feels like it is moving easier. So kudos to Fathom Arms, compared to other BCG's it looks like this one will increase longevity by decreasing friction points. If your looking for a buy once and cry once made in the USA bolt carrier group for your AR-15, I say take a look at this Fathom Arms Enhanced Bolt Carrier Group. It has done well for me.
Carrier Material: Case Hardened 8620 Steel
Finish: Black Nitride. This advanced low friction coating minimizes the need for lubricants.
Radiused Gas Key: 4130 Steel, attached with Grade 8 hardware, torqued to correct specifications, and then properly staked into a milled “valley” using a press stake to properly deform the metal. This procedure ensure proper positioning and gas key locking.
Ejection Port: Area is milled with added material for more strength and rigidity
Cam Pin: Hardened 4340 cam pin
Firing Pin: Mil Spec firing pin made of 8740 steel, center-less ground and Hard Chrome coated
Carrier Fits: AR15/M4 compatible style Rifles (i.e.) .223/5.56mm, .300BLK, 6.8SPC
Bolt Assembly: The Bolt Assembly is machined from solid round stock to TRUE Mil-Spec dimensions. The entire external surface, including the bolt bearing surfaces, is CNC ground after heat treatment to ensure proper and unaltered tolerances.
Material: Case Hardened 9310 Steel, Shot Peened
Finish: Black Nitride coated
Extractor: 4340 Steel, Magnesium Phosphate coated, Mil-Spec Extractor Spring, O-Ring, and Black Extractor Spring Rubber Insert, Shot Peened
MPI: Magnetic Particle Inspected
HPT: High Pressure Test
Bolts are lot tested under MIL-STD-1816 for both HPT and MPI