Originally Posted By RDTCU:
The lower is a standard 80% lower finished to spec, sans buffer tube. I machined the rear plug from SS roundstock. The upper is a DPMS slick flattop with the gas tube hole opened up for the larger gas key. The bolt carrier was a Bushmaster spare i had, chopped behind the firing pin and cleaned up with a lathe grinder. The barrel was a cheap (but accurate enough) Dez Arms 10.25 pistol barrel that came with a carbine sized gas port which had to be opened. The forened is a bushmaster carbine forend clearanced for the recoil system, the barrel nut also had to be clearanced. Gas key tube and gas tube are chromed, hardened die cast ejector sleeves, scraps from work. The gas block is a MI upper height rail block, with the gas tube hole bored offset and plugged. The SS muzzle brake is my own design, made from round stock (2 pieces, with the outer lip roll formed around the end). Next time i disassemble it (for duracoat) i'll be sure to take more pictures of the components.
Technically it's not a piston, it's a DI system with an extended gas key and a straight gas tube. I think a true piston would be too violent for the shortened bolt and would lead to bolt tilt and receiver wear. The beefy gas tube and gas key function as somewhat of a guide rod as well to reduce bolt tilt. Also, the charging handle is non-reciprocating and has a latch similar to a standard AR charging handle to keep it in place while the action cycles. I don' t know that i would want something reciprocating at high speeds if i were to put my thumb up the side of the handguard...
Thank You for the info.