Hello All,
This is my first post, so bear with me if I'm outside of the norm for posting here. I have an issue with my AR described below:
Bushmaster Upper
14.5 w/ mini Y comp
milled front sight
A3 upper all factory parts, with both and carrier from bushmaster
standard bushmaster lower
ACE skeleton shorty stock (entry size)
I've had the lower for a long time on a 20" upper and recently swapped it out to build this one. The only thing I changed on the lower is the stock to the ACE shorty stock, which came with DPMS CAR SPRING AND BUFFER.
The upper is brand new from bushmaster.
Upon firing i have a malfunction with some rounds. I mainly fire Lake City .223 FMJ 62grn green tip. They obviously have a little punch, and lock the action open and fire flawlessly 100% of the time.
Recently, i had opportunity to fire a variety of standard FMJ .223 55grn rounds varying from American Eagle, Federal, and Surplus. Opon firing these rounds, the weapon failed to lock to the rear 95% of the time and appeared to be shorstroking with a FTF about 50% of the time. I attempted loading 1 at a time to test lock back, and 2-5 rounds for feed and continued to have issue. I switched back to 62grn without incident.
I took the rifle to a gunsmith, the only one in the area that I know of to claim to be a AR smith, who stated that the bolt was fouled in the rear, and might not have been seating down to the rear all the way causing the FTF. But could not explain the failure to lock back.
On the range, I conducted a few test to attempt to locate the problem.
I switched bolts without change
I loaded one at a time to test lockback
Same results with lighter bullet
I loaded 2-5 rounds to test feed
50% FTF
I conducted an overtravel inspection of the carrier, which appeared to be unremarkable. The rear screw in the stock was removed to be safe, with no change.
The only problem that I can see is the the ACE stock came with DPMS internatls (IE: spring and buffer). The spring is black in color and appears to be heavier that a Bushmaster CAR spring. I have a BM CAR spring and buffer, and will attempt to change them out, but range time is unfortunately postponed to late in the week due to distance.
Please help me out, throw me some ideas on what it could be, or just entertain my dilema.
Thanks,
BCamp
NJLEO