Parts list:
Upper:
BCM blemished receiver
BCM Gunfighter CH
PSA Chrome BCG
Wilson 6.8 SPC II 1:11 16” lightweight barrel
Wilson Low Profile Gas block
BCM midlength gas tube
MI Free Floating G2 SS 12”
PSA A2 muzzle device
Lower #1:
POF receiver
POF LPK
Geissele SD-E
VLTOR A5 EMOD Kit
Lower #2:
Sun Devil receiver
PSA LPK with PSA trigger
POF Carbine RE
POF Carbine Buffer
POF Carbine spring
Range Trip 1:
Ammo: Federal 115gr Fusion MSR
Magazine: PMAG 20 rdn. I would only put 2-3 rounds of 6.8 in the PMAG at a time
Only brought lower #1 as this is the lower I would prefer to run this upper on. Initially had some FTE, the gun was short-stroking to such an extent that the brass wouldn’t clear the chamber and be ejected, this was for maybe 2-3 rounds then the rifle started ejecting but FTF.
Fix 1: Removed gas block and tube and inspected gas-port alignment, everything appeared fine, reassembled, and lubed up the BCG.
The extra lube appeared to help a bit, the rifle now chambered the next round most of the time but would not lock back.
Fix 2: used a known good BCM BCG in lieu of the PSA BCG.
No difference in operation
I fired 45 rounds the entire trip, the rifle locked back on an empty mag once.
Range trip 2:
Ammo: Fed 115gr Fusion MSR
Hornady 110gr VMAX
Magazine: PRI 6.8 15rnd (finally got it in the mail)
Tried Lower #2 right off the bat with Fed Ammo. Immediately had failures to feed the next round. Replaced with Lower #1 and it would feed the next round but would not lock back.
Hornady ammo did worse, failure to lock back guaranteed with approximately 50% failure to pick up the next round
Again I pulled the gas block and this time tried slightly different positions while firing a couple rounds. Noting the location of the carbon circle made by the gas block port at each position. I reverted back to the original position once I was 100% sure that circle was indeed created by the gas block port and the original position was correctly lined up.
At this point I used the PSA Bolt Carrier in my 5.56 build and it ran fine, also the gas rings on the PSA bolt are in good shape, a bit tighter than my other bolts, but its brand new while the others have a couple thousand rounds through them so I don’t think this is a BCG issue. Also the carrier without bolt slides forward into the receiver without any binding. So I don’t think gas tube alignment is an issue. I am not seeing any excessive carbon build up around the gas block so I do believe the seal is tight.
Anybody have any idea as to what else I can to narrow this issue down? I checked the gas port when I came home and there is no obstruction. And using just my eyeballs and a digital caliper it measures somewhere between 0.080-0.86. (Wilson advertises 0.082) I am surprised that it would not run with the carbine spring/buffer combination. Both these lowers run 100% with their uppers. 14.5” BCM middy on Lower #2 and 16” build with Noveske barrel on Lower #1.
I haven’t been able to find SSA’s hotter “Combat Loads” to try but it does suck not being able to run standard factory ammo.
Thanks guys
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