Ok let's play Diagnose the Franken upper
This is a long winded post as I wanted to make sure all important info was included. There is a summary at the end of the long winded narative you may want to read first.
I aquired a 14.5 inch upper in a trade. There are no marking on the barrel at all. It is cut in the M4 profile. The are no M4 feed cuts. It has the DPMS copy a Phantom flash hider. The reciever has no marks other that the splintered A forge mark. Seems to be well assembled. The BCG is DPMS. Gas key has an excellent staking job done to it. There are no issues visible with the gas system but have'nt removed the FSB. When I recieved the upper it looked to have little use. Now here begins my story.
I put the upper on my bushy lower with no name M4 extension. The lower also had the geissle DMR installed. I had several FTE and shortstroke like malfunctions. I also had a few double fires. So I proceded to start "fixing things". I tried to adjust the triger assuming this was causing my doubles and found the second stage adjustment screw stripped by the "professional" I had instal it. I removed the trigger and replaced the stock trigger. I stripped the bolt and found a worn or weak extractor spring with blue insert. So I replaced it with the BCM bolt upgrade kit. I then read up on short stroke and over funtion and decided the cheap no name buffer and spring had to go. So I purched a CS spring from brownells and an H2 buffer. While waiting for my buffer parts I installed the A2 stock and buffer. I ran 200 rounds of a mix of wolf, reloads and M193. I had one failure to eject on the M193. I put the rifle up dirty and walked away from it for a little while in frustration.
This saturday I took the carbine to the range after the local 3 gun match as there were tools and input to be found there. We test fired the rifle and on the first round the case got stuck inthe chamber. This was the first time this had happened. After banging the case outwith a GI rod I inspected it. It was abvious the brass had failed to seat properly an gas had blown by and left streaks on the outside of the case. The extractor ripped a chunk off the rim too. The rifle was dirty but... not that darn dirty. After the same thing happened on the next round we cleaned the chamber. Now we were back to running. However we still had some occasional failures to eject. Note since I replaced the extracor spring with the BCM kit my brass has been flying to 1 to 2 o'clock and there are visible signs of chewing at the front of my ejection port.
It was then suggested that I had too much extractor tension so I removed the O-ring and the rifle ran the next 40 rounds but still trying to eject brass through the front edge of my ejection port. When I got home I ran 30 rounds of M193 with my Bushmaster BCG and it ran well but with the same forward ejection.
Summary:
Patient discription: 14.5 mystery upper. No manufacturers marks just a splintered A forge mark. Barrel 1x9 chrome lined. BCG by DPMS. Round count est 1000. Geissle trigger improperly installed.
Symptoms past: Bolt bounce, freaquent fail to eject, occational double fire, sticking chamber when not really that dirty.
Corrective actions taken: Replaced no name CAR buffer and spring with H2 buffer and CS spring. Replaced extractor spring and insert with BCM bolt upgrade kit. Seriously cleaned the hell out of the chamber. Returned trigger to giessle for rework and installed stock trigger.
Symptoms current: Still occational fail to eject last 50 rounds have been fine will call it cured after 200. Ejection at one to two o'clock with visisible chewing at front of ejection port.
Any and all considered input invited please help the noob get his carbine working without it chewing up the ejection port or failing to eject. 200 round tests at $.40 per round cost $80 and I could buy a new upper with the cost of a few of these test runs.