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
If it extracts but doesn't ejects, and picks up a new round, then your extractor is letting go. You need a heavier extractor spring. Call Ken Elmore at 480 940-7397 and he will sell you a heavy duty spring that will solve the problem. If the case is left completely in the chamber, then you need to polish the chamber, but that doesn't sound like the issue here. Also, if the thing locks back on the last round, then you have enough gas to run it, so I wouldn't screw with the gas sytem.
Hi, Bob. Glad to see you have stopped 'lurking' and stepped up to the board.
Sounds like you bought yourself a hobby...but then who here has not? No big deal. We'll take it one stepat a time.
Get thee to a range. We need to establish some constants.
1) Put in an empty mag. Pull back the charging handle. Does the bolt/carrier hold back?
2) If the aboveis a YES, then insert a mag ith ONW round, release teh bolt-hold-open. Did the bolt/carrier go forward, strip the round, lad it and lock up?
3) If YES, fire the round. Did the bolt/carrier lock back on the empy mag?
NO: Try with aother mag or two. If still NO, then we need to look at
a) The bolt-hold-open spring
b) Are the pins tight at the front site tower?
c) Is the carrier gas-key tight? Staked down properly?
d) Does you hammer have a very long tail? Look at the base of teh disconnector to see if there is a wear spot where the hammer tail is hitting. This could be a problem which may occur if the hammer were changedat some point and the longer tail is interfering with the clearance between the hammer & the carrier...causing excess friction.
Get that far and let us know.
Meanwhile, take a 45 cal. chamber brush, chick it into a drill, put some JB bore paste (or any very light lapping compound) and run the drill at a medium speed to clean out & polish the chamber. Also, get behind those locking lugs! Brake Cleaner will do this very well.
Royce gave you a great start! I have one thing to add for right now. Pick up the empties, and look them over for any signs of a rough chamber or excess pressure: cratered primers; missing primers; a tiny bit of metal extruded into the ejection plunger or; rough texture imprinted from the chamber onto the cases. Report back to us on that too.