AR Gunsmithing for the complete idiot.

[Guest dotsun]

Ok, I need a good flaming so I'll post my latest attempt at home gunsmithing. My AR upper has had problems ever since I bought it and I along with Tower did some work on it. It was failing to feed and that problem is now corrected. Kudos to Tower on the suggested fix and the help getting it there.

My most recent problem has been light primer strikes. Some rounds fire normally, and then some primers would be indented with no love. (aka big boom) In my quest to solve the problem I replaced the hammer spring and also tried a new firing pin. Neither fixed the problem, in fact the new pin made it much worse.

So now we come to the idiot part. I have decided that in order to allow the firing pin to travel forward the extra thousandths of an inch required that I would file just a tad off the back of the bolt. Don't try to talk me out of it, because I've already gone and done it. I hope to try it out this weekend and I'll report back with the results. (Assuming that it doesn't explode into a million pieces leaving me in intensive care)

/dons flame suit

[Rightwinger]

uh oh....stay tuned.........next thread Tennessee Law, Wills, and YOU ! Are you Prepared by Dotsun.

Dotsun, was your bolt face fully engaging the extension? If it was having feeding problems already it sounds like it had alignment issues. Have you had the barrel off this AR? I guess since you already did it your gonna find out if it works but I have never heard of anyone taking some off the bolt to fix a light strike. Is it extracting when you manually run a round through it? If so then the round is fully seated against the bolt face and the problem is with hammer travel or something blocking the pin from traveling forward at full force. I see the logic of what your doing but have never heard of that type of fix. Shoot the first one behind some cover!

Edited February 28, 2008 by Rightwinger

[Im Neero]

I suggest pulling the trigger with your eyeball the first time, just to prove to the rifle that you are not afraid. Remember, they can sense fear.

[Guest Todd@CIS]

I suggest pulling the trigger with your eyeball the first time, just to prove to the rifle that you are not afraid. Remember, they can sense fear.

[Guest dotsun]

uh oh....stay tuned.........next thread Tennessee Law, Wills, and YOU ! Are you Prepared by Dotsun.

Dotsun, was your bolt face fully engaging the extension? If it was having feeding problems already it sounds like it had alignment issues. Have you had the barrel off this AR? I guess since you already did it your gonna find out if it works but I have never heard of anyone taking some off the bolt to fix a light strike. Is it extracting when you manually run a round through it? If so then the round is fully seated against the bolt face and the problem is with hammer travel or something blocking the pin from traveling forward at full force. I see the logic of what your doing but have never heard of that type of fix. Shoot the first one behind some cover!

The upper came fully assembled with bolt and carrier and I've never disassembled it beyond field cleaning. It cycles fine now, Tower and I cut some m4 feed ramps as the rounds were impacting too low initially. I'm not sure about the rest as I'm a gunsmithing idiot as the thread title suggests.

[Guest dotsun]

I suggest pulling the trigger with your eyeball the first time, just to prove to the rifle that you are not afraid. Remember, they can sense fear.

I intend to let Mike.357 shoot the first round since he mentioned shooting my guns in another thread.

[Guest sling]

I agree with right winger. Its probably blameable on human error to when they put the thing together. Are the primer strikes dead center or are they off to the side quite a bit?

Yeah i know that sounds silly but i've seen it before.

[Guest dotsun]

They're dead center. You know after looking at some of the rounds I just don't see how they didn't go off. The rounds are Malaysian M-193, it's not like they're the cheap stuff. I may pick up some different stock before my range trip this weekend just to be sure.

[Rightwinger]

I would definitely buy some other ammo and test it out. Most people worry about to much of a strike from their firing pins not to little. If you check next time your out (anyone with an AR) and shoot a round and then hand cycle the one that just fed in the chamber you will probably see a dimple on the primer already from the firing pin bumping the round as the bolt slams forward. The pin in an AR is free floating.

My bet now is the ammo with some dead primers. You can send me about 50 rounds and I'll test it in my RRA. I'll need that many to get a good comparative set of data points!

[Guest Scottech]

Was this the same issue we were talking about the last time we were at the range dotsun? I agree with RW. Try other ammo. Also check the ejector pin. It maybe pushing out on the round to the point where you're getting light strikes.

As far as ammo goes, I've had good luck with Rem UMC 55gr FMJ or 65gr JHP in both my Mini-14 and AR. It's pretty expensive right now. I really don't like Wolf but it's cheap and my Mini-14 has never had any issues with it and as far as my AR, I've only had those two issues of the lacquered cartridge sticking in the hot chamber and I had no FTF's. Check that ejector first.

[Guest sling]

Aye. Run some UMC or something through it other than that stuff. Could be hard primers but its doubtful. I've run a few hundred rounds of the stuff down my AR without problems. Bad batch perhaps?

[Guest dotsun]

Yeah Scott, it's the same problem. I will try some different ammo but I'm thinking that I had this problem with other ammo in the past. I just can't remember for sure. It really sucks getting old and senile.

[Mike.357]

I'll take you up on that offer to fire it Dave. I might be stupid but I ain't skeered.

I am betting your ammo is fine.

What drives the firing pin forward on them things?

[Im Neero]

The hammer.

[Guest dotsun]

Well, I'm now suspect of the ammo but not convinced. I bought a box of remington from WW and it worked fine. It's my understanding that military ammo has harder primers than the civy stuff so I'm gonna ask someone at the next tgo shoot to try a few of my rounds in their ar and see what happens. Stay tuned.

[Guest price g]

Did you install the barrel and adaptor?

[towerclimber37]

I'll take you up on that offer to fire it Dave. I might be stupid but I ain't skeered.

I am betting your ammo is fine.

What drives the firing pin forward on them things?

a ford Escalade....

Dave,

knowing your ar, I'm willing to bet that the barrel wasn't mated correctly to the receiver or a good barrel was mated to a crappy receiver. no worries...alot of toil and skull sweat will make you the go to guy for ar's here..

I have a couple of suggestions, NONE of which concern the bolt..

it's probably too late for that..but here goes.

1. take the receiver and have the barrel 'miked and gauged. I'm willing to bet that the barrel isn't in far enough, and that's throwing off your distance of the back of the rounds to the bolt face.

there ARE ways to mitigate this..but shaving the bolt is NOT one of them.

more than likely, your ar won't like some types of ammo simply because the cases are sized a bit short.

2. try different ammo.

3. buy a weaker firing pin spring or stone some of the metal off the firing pin retainer (thats the round metal at the back of the pin) but be careful..if its not completely flat on the bolt face side, you'll have off-center strikes..i.e you're back to square one and need a new firing pin.

I hope this helps you some!

Edited March 2, 2008 by towerclimber37

[Guest dotsun]

AR Fixed! I swapped some of the ammo out with the guy I bought it from and it did the same thing. This time, however, I was smarter than the rifle and brought some of my spare parts with me. I swapped the bolt out with an old one that had been collecting dust and voila she is fixed.

I have no clue what is wrong with that other bolt, but I'm considering turning it into scrap metal with a big freaking hammer. Or maybe one of these: http://www.stanleyfubar.com/

[Guest The Cat]

a ford Escalade....

3. buy a weaker firing pin spring or stone some of the metal off the firing pin retainer (thats the round metal at the back of the pin) but be careful..if its not completely flat on the bolt face side, you'll have off-center strikes..i.e you're back to square one and need a new firing pin.

I hope this helps you some!

When did they start putting firing pin springs in ARs?

You can check for the proper firing pin protrusion using calipers with depth gauge.

Milspec is .028" min and .036" max. Nominal is .032", so try for that.

If you're not getting enough protrusion, you have two options. Buy a new firing pin.... it should be right.

Or, if you want to use the pin you have, use the calipers to figure out how much more protrusion you need and have it turned in a lathe to remove that amount from the front of the retaining collar.