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AR15.COM
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4/16/2015 6:05:16 PM EDT
hello guys,

in all my years of building, shooting ar`s, i have never had a ftf . asking you guys if you might have an idea what
my problem is. the failing cartridge has bolt lug impressions on the casing just below the shoulder. the only change
i made to this particular ar was to install a lantac dragon to the bbl. the only other thing i could think of are the mags
i was using. they are standard pmags but the rounds in them have been in the mags (30 rds. full ) for about 5 months.

but i have been told that the springs they are using now are not prone to spring fatigue so you can load them and not
worry about that.  am i wrong?  could the difference in the gassing process from having the dragon installed have
anything to do with it? if so, what can i do to correct it? also, i you may be thinking about the quality of ammo i`m using
it is very good ammo & my own reloads to nato specs that have never failed me before.

if you need more info that i may have left out, please ask. this particular ar is my own build w/ 16in bbl.
just seems like the muzzle device may be the culprit because i have used full mags before that were sitting in my safe
for a good while ( in this rifle ) and this did not happen.

thanks for your time!
4/16/2015 9:44:24 PM EDT
[#1]
Can you clarify if it is a fail to fire, or fail to feed?  If the rifle used to work, but now doesn't, then you have to ask what has changed.

CY6
Greg Sullivan "Sully"
SLR15 Rifles
TheDefensiveEdge.com
(763) 712-0123
4/17/2015 7:21:38 PM EDT
[#2]
I'm going to venture a guess that your rifle is short stroking.

round fires bolt doesn't retract far enough to get behind the next round and kind of picks it up in the middle and smashes those two little dings below the shoulder.

4/18/2015 9:13:56 AM EDT
[#3]
failure to feed is the problem. your exactly right, short stroking. but why?

like i said, only thing i changed is to put on muzzle brake & was using full pmags
that have been sitting full for a few months.
4/18/2015 12:08:51 PM EDT
[#4]
What weight buffer and BCG are you using and is it carbine gassed or mid-length gassed?  Checking your gas key of leaks is always worth the time.
4/19/2015 3:55:10 PM EDT
[#5]
not sure of the buffer weight, is a 16in carbine. first thing i did when this happened is to check the gas system
& i also ran an iosso gas tube brush thru the tube to clean it and sprayed some brakekleen into the tube & blew it out
w/ my air compressor. using an m16 bolt carrier.

like i said, it ran fine til i put on the brake. so its either the brake doing something w/ the gas system
or the fully loaded mags that sat around for a few months.

i guess i`ll take off the brake and see if i get the same thing. i`ll still use some of the mags that were
loaded up and sitting around so i can eliminate the possible weak springs in the mags.
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