Hi there guys. I have been lurking here for some time, but just registered after buying a Bushmaster Shorty AK (serial # 107xxx). I picked is up used last week for $600. It looked as if it had not been shot much at all, but unfortunately looked as if it had been cleaned even less. Two different GI buddies looked at it for me and both commented that it was pretty dirty. One of them stripped it down to the point of removing the extractor from the bolt (the spring "thing" was blue, but a bit worn).
I was so excited to go shoot the thing that I did so without any preliminary cleaning. Needless to say it didn't function well at all. It short stroked to the point of only ejecting about 20% of rounds and wouldn't cycle far enough to pick up a new round from the mag, or far enough to lock the bolt open after the last round in a mag. The mags I have are used ex-military 30-rnd mags and one used 20-rnd. I was shooting PMC FMJ ammo. I cleaned the gun very thoroughly by disassembling almost everything in the bolt (with the exception of the ejector), removing buffer and spring for cleaning and lubing, cleaning the barrel(but I don't have a chamber brush, spraying carb cleaner (don't have any spray gun solvents right now, that was the best I could think of) down the gas tube. It seemed to flow out the end of the barrel pretty readily. The bolt moves very smoothly with the upper off of the lower and with the gun assembled. There is of course a bit more friction with the gun assembled as the bolt contacts the hammer. Everything feels pretty slick and smooth.
I then went shooting again and it seemed to work much better, but was rarely ejecting the spent cases. It would cycle far enough to pick up a new round, but since the spent was still in the receiver it would jam. Although once or twice it left a round still partially chambered, most of the time the round was extracted from the chamber, but not ejected from the receiver. A few stovepipes occured, but mostly the spent case was totally enclosed in the receiver. I have done a great deal of reading here about shortstroking, etc, but since there is no search function it is a bit different. What suggestions do you have regarding this? If I had to guess I would say the the ejector isn't pushing hard enough, or the extractor tension is wrong, but I don't know how to test or troubleshoot these issues. Thanks in advance. Bob