So I've decided to build my first AR. I want to replicate BCM's Recce 14 KMR13 ELWF Mk 2 rifle. http://www.bravocompanyusa.com/BCM-14-5-Mid-Length-ELW-KMR13-p/bcm-urg-mid-14elwf-kmr13.htm

On the link above it states, "These 14.5" mid length gas barreled upper receiver groups have been specifically tuned to be a very soft and fast shooting set up. They are a joy to shoot, but please feed it good ammo. With good milspec pressured ammo we have been running H buffers. We do not recommend using lower powered ammo. If using less than milspec pressured ammo, it may be best to run a standard carbine buffer."

When they say "specifically tuned" what do they mean? The Gas system? Is this "tuning" something I can do myself? Or is it proprietary to BCM?

Sorry if this seems like a dumb question, this is all new to me, thanks.

I think they mean the gas hole is sized for 5.56 ammo pressures. Some 14.5" mid length uppers have problems with steel ammo because it is too low pressure to cycle, so they drill a slightly larger hole. It sounds like they didn't drill a bigger hole to compensate for the shorter dwell time on this barrel, because they chose to prioritize softer shooting (less gas to the BCG).

It seems counter intuitive that they would mention an H buffer, which is for slightly over gassed guns, but again I suppose they are prioritizing smoother shooting.

BCM's 14.5 midlengths are notorious for using a minimum size/maybe too small gas port such that they sometimes have issues with non-5.56 pressure ammo.

Maybe dumb question, but why would you build a copy of a commercially available product? Maybe times have changed, but last time I looked into that, the parts would have ended up costing more than the complete rifle.

The satisfaction of putting a component together yourself is something that cannot be purchased.


I recently built a bolt carrier group from parts purchased individually. Could I have bought a complete BCG cheaper? Yes, but I would not have had the experience of staking gas key screws going that route.





 

My advice for building your 1st AR is to NOT do it over carpet.