AR Trouble Shooting


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rhp997
January 22, 2013, 11:48 PM
I just finished my first AR build- all parts are from Spikes Tactical with expectation to a Palmetto Armory lower parts kit. The BCG is from Spikes and has a chrome bolt assembly. It cycles brass ammo perfectly- however when I tried to shoot some steel cased I had a failure to fire on the 5th round. After reloading another magazine it happened again. I know the ammo is good because it functions properly in my other gun. Any ideas?178175

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ID-shooting
January 23, 2013, 12:00 AM
Probly nothing wrong with your build. Ammo is the suspect. What brand is it? I have bunches of wolf and herters in 7.62x39 and .223 that gave us same fits. Put some extra power hammer springs in our mini's and the problem went away.

Both mini's would fire brass ammo all day long.

Edit, didnt catch the part about the other gun. Maybe you do need a stiffer spring/heavier hammer. Are you getting primer strikes? Have you tried rechambering it after you wait for possible hang fire?

1911 guy
January 23, 2013, 01:25 AM
I'm betting it's a combination of hard primers in the ammo and an underpowered hammer spring in the rifle.

rhp997
January 23, 2013, 10:24 AM
The ammo is MFS 55gr FMJ Zinc Plated178195

madcratebuilder
January 23, 2013, 01:00 PM
Make sure the hammer spring is installed correct.

http://i32.photobucket.com/albums/d37/madcratebuilder/AR15/hammerspring.jpg

rhp997
January 23, 2013, 01:12 PM
Make sure the hammer spring is installed correct.

http://i32.photobucket.com/albums/d37/madcratebuilder/AR15/hammerspring.jpg

Thanks- ill check it out. The new build is midlength with a 14.5 pinned and welded barrel. The gun that the ammo functions fine in is a spikes carbine with a 16" barrel. I am also running my bolt dry.

highorder
January 23, 2013, 01:33 PM
I am also running my bolt dry.

Right there's your problem.

Lube the BCG like every manual, NCO, and experienced shooter tells you to.

IMtheNRA
January 23, 2013, 05:16 PM
If you have a .223 case gage, drop the steel ammo that did not fire into it. It may be a slightly undersized, giving you excessive headspace and a longer distance for the firing pin to reach the primer.

I have a Lake City round that did not fire with only a tiny firing pin mark on the primer, and when I checked it with the case gage, it turned out be way too short!

rhp997
February 19, 2013, 10:49 PM
Right there's your problem.

Lube the BCG like every manual, NCO, and experienced shooter tells you to.

Lubed my bolt as instructed in the manual- shot 12 rounds- and then FTF. Must be the ammo.

adelbridge
February 20, 2013, 12:03 AM
I had the same trouble with monarch brand steel case and a 4 lb spring.

Bartholomew Roberts
February 20, 2013, 01:16 AM
Just to clarify, the round appears to be chambered and when you pull the trigger, the hammer falls but no boom? Correct?

First thing to check - is the cartridge actually in battery. If the bolt is not completely locked (the cartridge is a tiny bit too long for example) the AR15 firing pin will not protrude (to limit out of battery detonation)

Second thing to check - is the primer indented and if so, is it the light little mark left by a free floating firing pin or a good, solid strike on the primer?

If your weapon is firing brass ammo with no problems and only this anmo causes an issue, it is 99.9% likely the problem is the ammo and troubleshooting the rifle won't help much.

OhioChief
February 20, 2013, 07:41 PM
Chrome bolt & carrier dry. Usually an issue. Usually you won't get as many rounds through as you did. doesn't happen as much after several hundred rounds, but they don't like dry too much. My 2 cents... and I've been there.

rhp997
March 22, 2013, 12:09 AM
Update to the problem- switched out the lower and functioned properly. I believe the problem is a weak trigger spring. Ordered a new one from Colt.

VA27
March 23, 2013, 12:48 AM
Update to the problem- switched out the lower and functioned properly. I believe the problem is a weak trigger spring. Ordered a new one from Colt.

Hammer spring.

rhp997
April 2, 2013, 07:49 PM
Changed hammer spring- problem solved.

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