Light Strike, need some help diagnosing.

Good day, all.

So, two weeks ago, I was competing in a tactical shooting competition and suddenly started having "feed issues" with my mags.

Or so I thought.

Yesterday, I was at the range, working on turning small holes into slightly larger ones with my A2, when I started practicing reloading drills (in light of previous experiences).

About six changes through, I had a failure. I pulled out the round and the magazine and examined them. Magazine was fine, round had a light strike on the primer. Literally, the lightest possible strike on a primer I think I have ever seen.

Wish I had a pic, but cannot seem to find the loose round in my range bag.

Anyway, I checked out my firing pin against my wife's SPR replica, and it looks like my pin is not as rounded as hers at the end.

Can anyone spec their properly functioning firing pin in a micrometer for me so that I can make an accurate comparison? Or maybe someone has the specs?

I am going to buy a micrometer today.

If there are any other ideas as to what could be causing a light strike, I'm all ears.

Lot of rounds through the weapon? The hammer spring could need replacement. Light strike to me indicates that the hammer isn't hitting the firing pin with enough force.

Best guess, fail to fire was the bolt not fully locked up as the hammer came.

So on that note, is the bolt locking back on the last round out of the mag, if yes, then what ammo was being used?

Ok, so, in an attempt to help further narrow this down, the ammo has been several types, but mainly XM193F and Wolf 62GR HP. The failure happened on both types of ammo. It also happened with PMAGs and with USGI mags.

The gun has about 1500 rounds through it, but the last 500 rounds has been the cause of the issues.

The bolt locks back on an empty mag, no problems with that.

Is it possible that the timing could be off or something is out of spec?

This is my go-to rifle, I hate to think that it would have so many problems after a nearly flawless first 1k rounds.

If I have to spend money to make it reliable, so be it, but I just don't want to replace pieces that are not broken.

If that helps anyone with troubleshooting, please help me get to the next step.

Also, to answer the hammer spring question, this is a PSA lower, with PSA parts kit. I did the work myself, and the gun passed all of the function tests.

I am certainly not beyond ordering another one if you guys think that is the problem.

I had similar issues on my first build because the hammer spring was backwards. It somehow still had enough force in it to work for awhile, but I eventually started getting a ton of light primer hits. I'd installed the spring wrong. You're positive it's in right? I'd just eliminate the cheap and easy solutions before I started looking at things that are much harder to fix. If you know 100% that the spring is in right and still providing enough force to the firing pin, it'd be time to go on to the next thing imho. Own any other AR's to compare against, or is this your first build?

http://i1124.photobucket.com/albums/l566/drifts14x/Snapbucket/72E336E7-orig.jpg

This is the picture I just took a minute ago.

This is what I thought it looked like on every pic I had seen.

If I need to do this differently, please let me know, I would love to be able to count on this thing again!

Oh, and yes, this and the wife's AR were my first builds. Both of them were done together (hers has worked flawlessly).

Hard to see in your picture, but it looks like the legs of the spring are on top. Is that right? If so, they should be on the bottom, like in this picture here.



If your spring is upside down, which looks to be the case (though the picture's dark, so I may be wrong!), that's definitely your problem. Switch it around and you'll immediately notice how much more tension you have.

Looks like hammer spring is upside-down.

Sounds like the other posters have it figured out. The way I check the hammer spring is to look in the receiver. If the legs of the spring seem level to the part line of the receiver, they are installed correctly. If they tilt down from above, the spring is backwards.

Another thing to check is to see if the carrier is fouled. I take the carrier out, push the bolt into the locked position and shake the carrier back and forth. I like to hear the firing pin rattling back and forth. I've had powder fouling muck up the firing pin and slow it down.

From the pic, your hammer spring is on backwards, which means that when your hammer is cocked back it is unwinding. Put the hammer spring onto the hammer so that when it cocks back that the spring is winding tighter. What is the configuration of the rifle (barrel length, gas tube type, stock system, type of buffer, type of bolt carrier). If the rifle has quite a few rounds through it, then it may be time to change your Action Spring (Buffer Spring). Also I recommend a detailed maintenance to the bolt carrier assembly, specifically clean the firing pin and firing pin track on the bolt (making sure that all fouling has been removed).


CY6
Greg Sullivan "Sully"
SLR15 Rifles
TheDefensiveEdge.com
(763) 712-0123

Looks like I have some work ahead of me :: facepalm ::

I guess I'll need to double check the wife's too.

Thank you for your help, I feel much better knowing that I don't have a bunch of out-of-spec parts (just a dumb operator).

It's an easy mistake to make. At least it's a ten second fix instead of a major issue!

Don't feel too bad...this is probably the most often made mistake in assembly.
It happens a lot.
And at least you had the cajones to ask for input.

Don't feel bad OP, the first one I put together had the hammer spring backwards and the disconnector spring upside down.


One positive here, bet you won't make that mistake again.

Two weeks ago.
http://www.ar15.com/forums/t_3_66/559717_Magazine_loading_Epic_Failure.html

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