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Posted: 6/9/2007 8:15:00 PM EDT
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Well, went to the range today...shot 100 more rounds through it. It did a little better, but still no lock back on about 50% of the last rounds fired. Although I thought I had solved the problem with the longer buffer. Range Report... 1st 3 shots, only 1 round in the mag at a time, new lower with long buffer, all locked back. I thought the long buffer solved the problem. Changed to original car length ACE buffer and 3 more shots the same way with only 1 round in the mag at a time. Locked back every time. Started putting more rounds in the mag, 2 or 3 at a time, about 50% of the time it would lock back. I did this for most of the 100 rounds...only putting between 2 to 5 rounds in the mag at a time, with about 50% lock back. Changed to different mags...same results. Went back to the new lower with long buffer...same results. What's really weird is that when I would only put 1 round in the mag, it seemed to lock back 90% of the time...with 2 or more rounds in the mag, it would lock back 50% of the time. Maybe just a coincidence, I don't know...but it did seem to lock back more often with only 1 round in the mag. I'm sure the mags are good because they worked fine in my others, with no problems at all. The GOOD NEWS!!! Absolutely NO FTFs/FTEs at all...and the first time I took it to the range I only had 1 FTE, so I'm happy with the functionality. Has anyone had this problem, and figured out what's causing it??? Any help would be greaty appreciated. As long as it's cycling good, I can live with this lock back problem, but I would like to fix it if possible. Here it is after the range time...I put my 3X9 compact scope on it that I use on my 11.5" and it did great. When I left, the center of the target was MIA. I shot about half on the 50 meter lane and half on the 25 meter lane. The stand that it's sitting on works great also...It used to be one of those rolling things that you hang clothes on. My wife had taken it apart and it was sitting on the shelves in the garage, so I cut it up, took the wheels off and replaced them with some adjustable feet that I had in the bolt bin, and drilled some holes for the short bungees to go through. And TADA!...it a bench rest. Works awesome... http://img184.imageshack.us/img184/7127/arp002xy0.jpg Ohhh...and I had an Officer quiz me about it...he was there trying to site in his EoTech on his 16" AR and he asked me if I had paid the $200 for the tax stamp and all. I said nope...it's a pistol. So he came over and checked it out, and said we would like to have one as well. |
Thanks for the reply LoneWolfUSMC... When I first read your reply, I thougth you might be on to something...but then I was thinking about it and I'm not sure, and here's why... I could see that having multiple rounds, or a full mag would put added pressure against the bottom of the bolt...which could slow it down a bit. But, this would probably affect the bolt during cycling...so I think that this would only result in the bolt not coming back far enough to strip a new round. And this thing has been feeding great. So even if you start with a fully loaded mag, when you get to the last shot, the mag still has zero rounds in it, and no added pressure against the bolt...so I can't see where there would be a difference in shooting one round or multiple...Or am I missing something? Basically when I was at the range and shot with 1 round in the mag, I would chamber that round...which left nothing in the mag. So this should be that same as last round out of a full mag. PolarBearBait suggested the piggy break...which should hold back pressure a little longer. I'm going to try that...but on this A2 setup, I just don't like the looks of a big flash suppressor...the A2 suppressor just looks at home on this one. So because of that, I hoping I can resolve this a different way. Thanks again, JuJu |
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Hey juju, What type of buffer are you using? Standard carbine, H, H2? What ammo too? I have a 7.5" A2 that had the same problem. I changed to a full auto bolt carrier (for extra mass) and now it functions perfectly. Adding a heavier buffer would probably have the same effect. |
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I'm using the buffer that came with the ACE pistol kit...I guess that it's the standard CAR buffer weight. Might have to try an H2...that would probably be the cheapest test. I got the ammo local..."Georgia Arms". They usually sell at the gun shows, but I live close to the place where they make it, so I pick it up there. It's very good stuff...and never had a problem with it. But it's just the regular 55gr FMJ that I got in a case. So, the full auto carrier has more mass at the rear...which means more weight, so I can see how that might help. I'm assuming that it's legal to use that carrier, right? I thought the extra metal in a full auto carrier was the only difference in a semi vs. full auto bolt/carrier. Is there more to it than that? Thanks for the info! JuJu |
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The Ace kit probably is a standard car buffer. The cheapest heavy buffer to get is a 9mm one which runs about $25. I would try that second. First I would try mil spec ammo like WWB. I know Geogia Arms makes good stuff, I see them at all the shows down here but, loading ammo hotter means using more powder which, costs more money. I used a full auto carrier just because it was what I had handy at the range when I was trying to get the 7.5" to work. The auto carrier does have a little more meat, thats the only difference, Here's a vid of the upper in action on my buddies RR. 7.5" upper |
| I beg your pardon for the upcoming insult but you're not limp-wristing it are you? You no longer have it supported by your shoulder so you gotta make sure the gun's not moving enough to counter the cycle. I'm pretty sure i remember there being gasport issues as well with the shorties. Something like they need a larger hole for gas to do it's job because the barrel is short enough the gas just goes on out the end behind the bullet instead of up through the block and into the action like it's supposed to. Either way it seems like some force is not allowing the bolt to go back far enough consistently. Could also be a malfunction in your bolt holdback. Is the lower new? I can only assume that it is and one of the aformentioned suggestions is the solution. |
NICE!!! I would love to throw a few down range like that one day...never had the pleasure to try a full auto though. Thanks for all the info... For 25 bucks, I'll probably go ahead and pickup the heavier buffer, and try it...the ammo would probably solve the problem right away, but I've already got a couple cases of "Georgia Arms" FMJ for the range. So I'm going to try to get it to work with that if possible. Ammo prices are going up! he I just want to make sure that I'm all legal...but I thought that the parts in the lower is what would get you in trouble. Thanks again for the help!!! JuJu |
No problem with the question at all...as this could cause the problem I'm having. But no, I don't think that's a possibility here, because most of the testing was done on the bench rest stand that's in the pictures above...It holds the pistol VERY secure, and I was holding it pretty tight to keep it from moving as well. And yes, the lower is new. But I've tried multiple lowers, which work fine on my 11.5s and 16s...so you are correct, it's definitely related to the gas pressure/cycle time issue. So this is why I'm trying to find an easier fix using heavier carrier, buffer, etc...if possible. The barrell gas port hole was supposed to be drilled out to be the correct size for a 7.5", and I would assume that it is, since it's cycling great. But like you mentioned, the gas/cycle time is reduced big time with a 7.5", which is what's causing this problem. So I'll try a few of the things suggested and let you know how it goes... Thanks for all the help...you guys are great!!! |
| I had a similar problem w/ an AR once. Wouldn't lock back after the last round. Wasn't mags, or insufficient gas. I had a problem w/ a bad parts kit from model 1 sales. The bolt release was binding & the spring was too long from what I could determine. I pulled the bolt release & cleaned up the edges where it touched other parts and it got better. When I took a couple of coils of the spring my problems went away. |
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