View Full Version : Need help with an NFA rifle!

June 24, 2008, 08:08 PM
I have a Bushmaster Lower with a 10.5 inch Delton Upper. The entire upper is Delton. I use this rifle at work on the SWAT team and had to requalify with it today. There was a little problem.
Some history. I have put about 500 to 600 rounds through this setup since I SBR'd it last summer. the only time it jammed was the first time I qualified with it for work. The last 2 rounds I had to fire FTE and the spent case got stuck above the bolt carrier. The new round was partially chambered. I had to dig the spent casing out with a knife.
Today I fired the first few strings of fire without a hitch, roughly 20 rounds. After that my gun would FTE and jam everytime i tried to shoot. I tried different mags (the old military ones i use for practice, the brownells mags with magpul internals and even my team leaders magazines) with the same effect. Twice when my team leader was shooting his gun jammed. Then we went onto ammo. I had some FMJ I use at 3 gun competitions, my duty ammo and some of the American Eagle FMJ we were using to qualify with and all 3 types did the exact same thing. We then pulled the rifle apart to check the extractor. It appeared to be in good shape. I think we have eliminated magazine malfunctions and ammunition. I am going to have a new extractor put in tomorrow and bring my other AR to the range on Thursday to see if swapping out the bolt carrier groups helps. That is if the new extractor doesn't fix the problem.
Does anyone know if the extractor springs have to be beefed up or not? I read on Brownells that a drop in kit with 4 times the strength of the factory spring is made especially for short barelled AR's.
Anyone have this problem and know how to fix it?
Thankyou for all the help

David Hineline
June 24, 2008, 09:50 PM
With minimal data, my first guess is the allen cap screws on the gas carrier key are loose.

June 25, 2008, 02:43 AM
So it could be something to do with the gas system instead of the extractor itself. I plan on cleaning it thoroughly and I will check the screws.

Thanks. I am still looking for suggestions until I get it working correctly.

June 25, 2008, 10:02 AM
May be a gas port issue.

June 26, 2008, 04:46 AM
The screws were not loose. That is what i thought too. Replaced the extractor with the heavy duty drop in kit. Will fire some 1 round magazines out of it today to see if the bolt locks open. If it doesn't then i know it is a gas issue. If it does then I don't know what it could be.

June 26, 2008, 02:07 PM
Fixed it!
Put 200 through it and then qualified with it.
Works great now.

GA Limited GM
June 28, 2008, 07:23 AM
Well? What did you do to fix it?

June 28, 2008, 07:36 AM
Replaced the extractor with the heavy duty drop in kit. ..