First range report - A few lite primer strikes

[Tally XD]

I did a search here but it yielded nothing I could find to use for a diagnosis. I am on dialup still and AR15.com is just too graphics heavy for me to use.

As a lot of you know I finished my AR yesterday and took her out to shoot a few rounds. Out of the 70 rounds fired, I got four or five that never fired. Lite primer strikes looked to be the culprit.

Some of these were loaded back into the magazine and fired on the next go around.

While it did seem to get better the longer I fired it, I wanted to check and see what usually causes lite primer strikes on a brand new gun?


UPDATE!! Hammer spring was incorrectly installed! This caused lite primer strikes. It is now fixed and runs great with ZERO problems! Make certain of your instructions and install y our springs correctly!

[John A.]

Make sure the hammer spring is installed correctly.

The legs of the spring go over the trigger pin instead of under it against the floor of the receiver.

Put the trigger in first, then install the hammer.

This will likely take care of the light strikes.

Edit: It may also be the ammo, but not likely.

[Tally XD]

Hammer spring is correctly installed. I was using Remington UMC ammo from Wal-Mart, but like you, I doubt it was ammo.

[Deadcenter]

Originally Posted by Tally XD

Hammer spring is correctly installed. I was using Remington UMC ammo from Wal-Mart, but like you, I doubt it was ammo.

UMC is known to be spotty. Tho for for having soft primers than hard :-p I would try some better ammo before I blame a brand new rifle.

[agalindo]

I had the same problem just after building mine and it turned out to be the hammer spring. Installed it backwards. I could have sworn I installed it correctly but it wasn't. Notice in the pic, the arrow point to the spring legs, for some reason on my hammer I put the spring in with the "open end" of the spring facing down so the legs were on the other side where the thumb is.

[Tally XD]

Buddy of mine gave me some true 5.56mm Winchester ammo today. Out of 20 rounds, nearly half were fail to fire.

I then loaded up another 10 rounds of the Remington .223 I got from Wal Mart and it fired each and every round with no fail to fire. I dunno whats going on here. I have removed the upper and inspected the trigger group . . . again for the third time. All looks exactly as it should. I removed the bolt and disassembled it. Found nothing wrong there. Firing pin looks to come out far enough to not have lite primer strikes. Fired brass looks the same as the unfired brass, same dimple in the primer.

I guess I am gonna have to take it to the armorer where I bought the parts and let him check it out. If it is this undependable I cant have that.

What does headspace do? I didnt check headspace because I didnt have the guages and AR15.com says it is unnecessary with a brand new rifle.

[Tally XD]

Something I just noticed though after inspecting both fired and "dud" rounds. I noticed that the dented but unfired primers seem to be set deeper into the cartridge casing than on the rounds that fired. The fired rounds casings have primers that are flush with the rear of the casing. The unfired rounds look to be set in a slight bit, yet they are very well dented by the firing pin.

Could these have been set too deep from factory or could they have moved when the firing pin struck them?

[John A.]

Originally Posted by Tally XD

I didnt check headspace because I didnt have the guages and AR15.com says it is unnecessary with a brand new rifle.

First off, you said in your first post: As a lot of you know I finished my AR yesterday, so that sounds more like a build than a complete rifle.

Second, the info I qouted you on about headspacing not needing checked is TOTAL and COMPLETE BS and is just one of many reasons I don't like arfcom. Too many sheeple talking out of their a@@.

Any firearm built from parts (especially from various manufacturers parts and specs) should have the headspace checked prior to firing the weapon after assembly. Though any complete upper built by a major manufacturer should be checked prior to leaving the factory that built it if it's shipped complete.

It is also sound advice to periodically check the headspace on well used AR's every 7-10,000 rounds or so whether factory assembled or not while doing routine maintenance too.

Headspace is basically the chamber dimensions and the depth the round seats when the bolt is closed.

Here's a good link that explains it more. And there is enough of a difference between a 5.56 round and a .223 chamber to not let the bolt close enough to lock and cause a fail to fire if you're trying to shoot 5.56 out of a .223 chamber. (.223 and 5.56 IS different no matter what you hear on the internet)

Measuring Headspace



Here's the specs for .223 and 5.56 differences (pic courtesy of Ammo Oracle)
http://www.ammo-oracle.com/body.htm


5.56 v. .223 Remington specification.

[Tally XD]

Originally Posted by John A.

First off, you said in your first post: As a lot of you know I finished my AR yesterday, so that sounds more like a build than a complete rifle.

Second, the info I qouted you on about headspacing not needing checked is TOTAL and COMPLETE BS and is just one of many reasons I don't like arfcom. Too many sheeple talking out of their a@@.

Any firearm built from parts (especially from various manufacturers parts and specs) should have the headspace checked prior to firing the weapon after assembly. Though any complete upper built by a major manufacturer should be checked prior to leaving the factory that built it if it's shipped complete.

It is also sound advice to periodically check the headspace on well used AR's every 7-10,000 rounds or so whether factory assembled or not while doing routine maintenance too.

Headspace is basically the chamber dimensions and the depth the round seats when the bolt is closed.

Yes, this rifle was assembled piece by piece by myself. Every pin, bolt, screw, spring. All assembled at home.

To my knowledge my chamber is 5.56mm. I asked for that strictly and was told that is all they sell. It is a CMMG midlength 16" 1:7 twist chrome lined bore/chamber. The shop I buy from is reputable and has a good clientele. Still, I will affirm my choice Friday.

Oil might have been my problem. I am one to never put a lot of oil on a gun but it seems, from what I am reading, a rifle, such as an AR, needs more oil than a typical pistol. I have never owned such a rifle until now and I am not schooled on proper oiling.

After my troublesome session this afternoon, I took the bolt group out, cleaned it and the firing pin and put more oil around everything there. Even the charging handle slot got oiled.

I then loaded up 10 rounds of Remington UMC from Wal Mart and it fired without a hiccup. All 10 rounds went off perfectly. I initially had trouble with this ammo a few days ago when I first took it out on its maiden voyage to the range.

[John A.]

From CMMG's website:

Barrels are engraved CMMG MPC 5.56 NATO 1/7

Checking the barrel for markings probably wouldn't hurt.

AR's do prefer to run wetter than most guns, but unless it was so dry the bolt wasn't closing all the way, I don't know why you'd have a lot of failure to fires. Most times dry or dirty AR's just don't cycle well is all and you'll have failures to feed altogether and stovepiping.

The next time you have a fail to fire, try pushing in on the forward assist to make sure the round and bolt is seated properly, but don't be too forceful with it. Just push in enough to make sure the bolt is fully closed. If it's not, you'll feel it.