assembled the upper and fired a few test rounds this afternoon.
DSA m4 upper, de-branded ex military bolt carrier, cav-arms polymer lower with a1 stock set, standard CAR buffer and spring, trail mix lower parts kit, D&H steel mags with magpull followers 30 rounders.
two bolts were tried one 6.8 SPC that was cut slightly oversize and one 7.62x39 standard bolt with 5.56 extractor.
the weird thing is each of the bolts worked with no problems. ironically the 7.62x39 bolt had no problems other than tossing the empty cases on my right cheek as i shoot left-handed. the slightly tighter fit on the 6.8 bolt (even the loose 6.8) one did not have this problem.empty cases cleared my face even left-handed firing.
empty cases were checked over for any kind of oddities with either bolts and none were found.
\rounds fired 55 rounds each bolt wolf 70grain 5.45x39 a total of 110 rounds were fired.
no feeding problems, failures to fire or extraction problems were encountered.
notes i only loaded the mags to 24-26 rounds.
didn't test for accuracy due to excessive temps and humidity. the AC and the ice chest was calling me!!
i'll probably put this upper on the DPMS lower with a 6position stock. the a1 shortie stock is a bit short and the cases hit my face. maybe a slightly longer stock like an a2 or an extended adjustable may solve the problem.
this is a super easy conversion. all you need is a barrel and a bolt and you can be cooking with the 5.45x39. the CAR length seems very smooth in operation. i suppose the so-called over-gassed set up on the 16inch barrel might help the slightly underpressure commie ammo? all i know is the damn thing flat works.