Dwight Stearns Posted June 12, 2009 Share Posted June 12, 2009 (edited) While shooting at the Midwest 3-gun last week my shooting partner's ar-15 started doubling. It did it once on stage 6 and we thought(hoped) it was an isolated incident. Well he started stage 8 and had immediate trouble. The second time it did it the RO stopped him (good Job RO). We replaced his lower with the lower off my back-up so he could reshoot that stage. WE then went to the side range with an RO to try and figure things out. His upper/lower set-up (which included an AR Gold trigger) was giving him numerous double's tripples and even a quad. His upper with my lower (standard ar trigger) continued the parade of multiple shots. He finally decided to finish the match with my complete back-up rifle and did so with no trouble. Upon our return home we again tested his rifle with similar results plus one shot while on safe when he chambered the first round. (Sound familiar Kurt?) We finally changed to another bolt. So far nothing unusual in about 100 rounds. We are pretty sure we have narrowed it down to the bolt. The hammer is falling on all those doubles (full firing pin strike). My guess is that something in the bolt (or possibly the upper reciever) is out of spec. Please pass on any ideas on what to look for to finish diagnosing the problem. Edited June 12, 2009 by Dwight Stearns Link to comment Share on other sites More sharing options...
HSMITH Posted June 12, 2009 Share Posted June 12, 2009 I'd look for a stuck firing pin..... Link to comment Share on other sites More sharing options...
astephenson Posted June 12, 2009 Share Posted June 12, 2009 I'd look for a stuck firing pin..... That's what I thought immediately as well, since it happened when the upper was on a different lower. Link to comment Share on other sites More sharing options...
kurtm Posted June 12, 2009 Share Posted June 12, 2009 Mine was kind of "self induced". I had just got one of the LWR bolts from John at J.P. and I had just put it in my rifle and test fired it 5 rounds and then went to the match. Upon getting home I found the whole inside of the bolt packed full of "shipping grease" nice thick and heavy, I am now surprised by two things...that it didn't slam fire more...and that I am relearning simple stuff again! All I had to do was pull the darn thing apart apply a moderate amount of cleaning and THEN go shoot, not the other way around. Now I just need someone to find and return the couple of years that slam fire scared out of me! KurtM Link to comment Share on other sites More sharing options...
Dwight Stearns Posted June 12, 2009 Author Share Posted June 12, 2009 Kurt, I'll bet it did scare you. You followed all the safety rules (safety on, finger out of the trigger guard, muzzle in a safe direction) so all it turned out to be was a loud noise. My squad was waiting on deck so it startled the heck out of us too. I'll chedk the firing pin next week. That may be the culprit especially since it seems to be getting worse. Any other ideas, let me know. Thanks Link to comment Share on other sites More sharing options...
Chris Keen Posted June 12, 2009 Share Posted June 12, 2009 You know some guys pay 10's of thousands of dollars to have an AR-15 that triples. Yours was FREE! Link to comment Share on other sites More sharing options...
Dwight Stearns Posted June 12, 2009 Author Share Posted June 12, 2009 Not if ATF Catches me..... Dwight Link to comment Share on other sites More sharing options...
ken hebert Posted June 13, 2009 Share Posted June 13, 2009 (edited) Definately not worth it. Pull that sucker apart. The ATF ain't screwing around lately, especially with AR's. Edited June 13, 2009 by ken hebert Link to comment Share on other sites More sharing options...
Chris Keen Posted June 13, 2009 Share Posted June 13, 2009 (edited) Sorry guys, it was just a joke. You are 101% right. I think it's ironic how many guys spend $10,000 to have an AR-15 that does that. And then when it does it for free on it's own accord ...... we FREAK OUT!!! Edited June 13, 2009 by Chris Keen Link to comment Share on other sites More sharing options...
Trini Posted June 13, 2009 Share Posted June 13, 2009 I have an SP1 that did that several times... Had to replace the hammer and disconnector to getting running right again. T Link to comment Share on other sites More sharing options...
benny hill Posted June 13, 2009 Share Posted June 13, 2009 Sounds like the hammer was slipping off the disconnector to soon. Link to comment Share on other sites More sharing options...
John Dunn Posted June 13, 2009 Share Posted June 13, 2009 This is a great topic. I understand the possibility of slam fires, and the reason ammo manufacturers use hard primers in AR ammo, but it would seem that grease on the FP would resist firing pin inertia and decrease the likelihood of slam fires. I also don't understand how an out of spec bolt would lead to doubling. What dimension would have to be out of spec? My guess would be the trigger/disconnector is out of whack like Benny suggests. Link to comment Share on other sites More sharing options...
Wap wap Posted June 13, 2009 Share Posted June 13, 2009 haven't worked with the gold trigger, yet, have you ruled out the thickness of the bolt carrier that actually cocks the hammer, it may not be pushing the hammer far enough, also--- on two stage triggers it is possible to feather the trigger to get multiples by not allowing the trigger to go forward, (somewhat like shooting a glock). some guys are so good at this they can rest the gun on their hip and feather the trigger for continous fire, somewhat like the Hellsfire device. Link to comment Share on other sites More sharing options...
Dwight Stearns Posted June 15, 2009 Author Share Posted June 15, 2009 (edited) Haven't had the opportunity to try the suggestions as of yet. The bolt seems to be fully cocking the ar gold hammer. We had thought about the bolt might not be fully cocking the hammer but that doesn't seem to be the case. If we dry fire then charge the bolt very slowly then open the receiver, the hammer is cocked on the primary sear where it should be. I still want to investigate the sticking FP. Will do that tomorrow hopefully. Thanks to everyone for the help but don't stop now. Keep the ideas flowing. This is a learning experience. Dwight Edited June 15, 2009 by Dwight Stearns Link to comment Share on other sites More sharing options...
JamShot Posted June 16, 2009 Share Posted June 16, 2009 (edited) How about giving a try for a lighter firing pin? I had several doubles (with factory ammo), after few years of trouble free shooting, even when swapping the lower. I think that gas rings were worn causing regular firing pin starting to slam fire with all that speed given by lightened carrier and no-mass buffer. It ended when I tried lightened firing pin, regular firing pin with slide glide or fresh bolt with stiff gas rings. Now I have new gas rings, lightened pin and oil around it just to be sure... Carrier pulls firing pin when bolt is extended and in this sense crud around firing pin doesn't cause slam fire. Titanium firing pins didn't convince me... ...So firing pin after diet: Edit: Pic should be visible to everyone now. Edited June 17, 2009 by JamShot Link to comment Share on other sites More sharing options...
Dwight Stearns Posted June 17, 2009 Author Share Posted June 17, 2009 (edited) Hi all; We tested the bcg and the firing pin was not sticking and wasn't over length. I'm back to the suspicion that something in the bcg was tripping he hammer. A sticking fp might account for doubling but triples and quads seem impossible unless it is the hammer that is setting the round off. I can see a double from a stuck fp but it seems the second shot would push the fp back out of the firing pin hole and the third and fourth shot just wouldn't happen. We called Ronin Coleman about the AR Gold fire control group and he doesn't believe it is the fault of the fcg but asked to see it just to make sure. He said he would have the group back to us by the end of the week. The bcg is Rock River. Maybe the bcg is out of spec but I wouldn't know what to look for and have no idea how an out of spec bolt could even cause the problem. Thanks to everyone for the help. I'll report back if/when we figure something out. Dwight Edited June 18, 2009 by Dwight Stearns Link to comment Share on other sites More sharing options...
HSMITH Posted June 18, 2009 Share Posted June 18, 2009 If it did it on a couple of lowers the trigger group isn't the cause. Link to comment Share on other sites More sharing options...
Dwight Stearns Posted June 18, 2009 Author Share Posted June 18, 2009 That's my conclusion but Ronin wanted to make sure. Dwight Link to comment Share on other sites More sharing options...
springy Posted June 18, 2009 Share Posted June 18, 2009 firing pin after diet: Edit: Pic should be visible to everyone now. That is one fine looking firing pin!! Link to comment Share on other sites More sharing options...
John Dunn Posted June 18, 2009 Share Posted June 18, 2009 What primers were you using? Link to comment Share on other sites More sharing options...
Dwight Stearns Posted June 19, 2009 Author Share Posted June 19, 2009 We were using winchester wsr primers. Dwight Link to comment Share on other sites More sharing options...
kurtm Posted June 19, 2009 Share Posted June 19, 2009 Double check that you didn't get small pistol primes instead. It wouldn't be the first time I got miss labled primers from WW. Had a whole batch marked large pistol on the case and marked large pistol in the 100 box, but the individual boxes of 100 were reall large rifle. KurtM Link to comment Share on other sites More sharing options...
Dwight Stearns Posted June 19, 2009 Author Share Posted June 19, 2009 Good idea but we have already checked that. I'm still thinking the hammer is being tripped. Examination of the brass involved in the "extra Shots" shows identical firing pin hits to the intentional shots (first shot). We will recheck the fcg when it comes back from AR Gold with the replacement bcg. We fired about 30 rounds with that replacement bcg with no problem before we sent the fcg off to be double checked. Thanks for the help. Dwight Link to comment Share on other sites More sharing options...
Dwight Stearns Posted June 19, 2009 Author Share Posted June 19, 2009 We received the fire control group back from AR Gold today and took the rifle back to the range. With the original bolt carrier group (rock river) the rifle doubled in the first 15 rounds. We then took a bcg out of a back-up rifle and have close to 100 rounds without a problem. The rock river bcg was then put into the back-up rifle and no problems in around 50 rounds so far. Something in the Rock River bcg was tripping the hammer but only in one lower. We will put more rounds through both rifles when we have access to a better range so we are getting in some good practive while we test for problems. Still don't understand it but so far the problem seems to have been corrected. Time and ammo will tell. Thanks to everyone for helping the ignorant. Dwight Link to comment Share on other sites More sharing options...
Dwight Stearns Posted June 24, 2009 Author Share Posted June 24, 2009 Ok I think we have the problem finally figured out (along wit the help of Ronin Coleman) (thanks Ronin) . The Rock River BCG appears to be a little under spec and (you were right Wap wap) the hammer was not being cocked all the time. The BCG on any ar 15 does not fit very snug in the upper reciever. There is a lot of room for play as the BCG cycles. When we were cycling the bolt by hand, the charging handle was pulling down on the carrier which was putting pressure down on the bolt so the hammer was cocked without problem. But when the rifle is fired there is no downward pressure on the carrier. Add in the built in tolerances in the fit of the carrier to the upper and the carrier was riding up over the hammer enough to fail to cock the hammer. Replacing the Rock River BCG with a Saber bolt fixed the problem. And as a bonus, the RockRiver BCG appears to work just fine in the Saber. Thanks to everyone. Dwight Link to comment Share on other sites More sharing options...
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