There was another FTF thread here, and I think mine may be similar. I have a RRA 20" A2, and have not had the chance to shoot it a lot. The first trip was just to sight in, and I put 40 rounds through it with no problems whatsoever (it's an indoor range with a 1-hour timelimit, and moving the sighting-in is time consuming). I shot LC (lot 2) and used the factory Colt made 10-rounder.

So I went back out today to sight in a scope and loaded up 3 round. First two went fine, the third I couldn't pull the trigget. Turns out a cartridge had been lodged between the top of the bolt and the roof of the receiver ! The bolt had jammed into the cartridge in the rear third length-wise. I was finally able to use a screwdriver to pry the front of the cartridge down out through the mag port (put a couple of scratches inside of the receiver too :-( ). This was the same magazine, same LC ammo. I then had two more problems out of 30 rounds, with one unfired round having been ejected along with the fired round, and the other getting jammed in the front third by the bolt.

This really sound like a magazine problem. I wonder if there is a way to incorrectly insert the magazine to cause this.

I subsequently shot 10 rounds through a DSI/Sanchez thirty rounder without incident in a relatively quick fashion (so as not to draw the ire of the rangemaster).

Does this sound like a magazine problem, or should I have the feed ramp/rifle checked out ?

Thanks,

Martin

copied from the other post...

I had a similar problem.  Turned out the bullit was popping out of the mag too easily.  When the bolt returns the round was just laying on top of the mag with the nose too low to get fed properly.

In my case, I had to bend the lips of the magazine down to conform to the case of the top round.

I've used the same 20 round mag with minor adjustments now and then for about 4 years.  I estimate more than 6000 rounds have gone through the thing.  It's well worn but very reliable.

Billski told of us a magazine fountain test.  Fully load the mag and bang the bottom on something.  Not so hard the mag is damaged but hard enough to get the bullits to rebound into the mag a little.  In a bad mag, the bullits will come spewing out.

Just in case anyone cares - it definitely seems to be a magazine problem. I put a bunch of rounds through the AR today, all USGI mags, and not a single problem. I was really worried since the last outing that the rifle had a problem, but it seems to be related to the crummy design of the Colt 9 round magazine with it cheesy flat follower.

Time to get some 20-rounders for the indoor range when shooting off of a rest....

That is a clasic case of loose feed lips.  To clear this jam don't pry on the cartrige.  The cartrige is stuck between the front ot the charging handle and the top of the bolt.  The trick is to move the bolt/carrirer back without using the charging handle.  Use a dowel or a cleaning rod section to push back the bolt, then the cartrige will fall out.

i have the same thing happening to a gun of mine, any mag does it, and all of the mags i have tried work perfectly in all of my other ar15 rifles, changing mags, complete bolt/carrier groups does not help, the chamber is perfectly clean, non chrome barrel, and the gas tube looks good, it always locks open on the last round, never has done the short stroke, so wassup.....

I think i found the problem!

damaged buffer assembly, took the whole gun apart, every pin/spring/bolt ect

the rear of the buffer assy is severely distorted, the bumper part, i replaced with a new spring and buffer, will give a sitrep tomorrow.

i said that the gun was not short stroking, but maybee it was very slightly restricted by the buffer deformity, and was not letting the bolt go back far enough, or fast enough, the bolt may have came back far enough to get behind the next round in the gun, but not far enough to give a pause for the spent case to finish moving out from in front of the bolt, and when the bolt rode home, it took the spent case with it, who knows?

I hope everyone gets their rifles working again. I feel sooooo much better since mine is working again. It's like having a sick kid when something ain't working right....

avenge,

If the rear of your buffer is damaged then something is not right with your rifle. Something like overfunction, lower receiver extension too short, buffer spring too weak, buffer too light, upper buttstock screw too long etc. Make sure to find out WHY the buffer was getting damaged.

You may not want to use a metal screw driver.  The scratches aren't the best thing in the world, and from what I gather it's never good to mess with a jam using a metal anything.  Use something plastic or wood so that you reduce any damage and don't accidentily hit the primer.  That would, well, kinda hurt.

i replaced the buffer and the buffer spring, problems went away, it seems that the buffer actually contacts the reciever extension when the action cycles, well the buffer came from one of the cheapo parts places, i will not mention the name, but it had the bumper, or rubber on the buffer pressed into the rear of the buffer, there was no pin to hold it in place, it pushed into the rear of the buffer assy, and part of the rubber had swelled and was making contact with the spring, slight drag i guess, it could not be felt when charging the firearm, but upon inspection it was obvious, the gun is a preban car