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Posted: 4/9/2011 10:35:42 AM EDT
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Hi Folks,
I just got home from the range with my new Evolution upper. I put 200 rounds of CCI Mini Mag through it and 30 rounds of bulk Federal. I'm pretty happy with it overall. It was defiitely accurate but I did have a couple problems. First thing was the mags fitting very tight in the mag well. I'm using a PSA lower and I've read quite a few reports of pmags being pretty tight so I'm thinking it's probably tolerances on the lower machining rather than the magazines. The main trouble was with the bolt locking back before the mags were empty. It only happened 12-15 times out of the 230 rounds I shot but I would sure lie to figure out what the problem is. Anyone had this issue? There were a couple times that it happened in the middle of a magazine filled with 10 rounds but usually it was after the first or second shot. Should I try adjusting the screw for the little BHOA thing that sits between the upper and lower? Any other ideas on what it may be? Thanks, Chris |
| You might want to check the CMMG industry forum. It's my understanding they are making their magazine a tad on the large side so you can adjust the fit of the magazine to your mag well and bolt hold open device. There have been a few threads regarding this tweaking. I don't own any of the newer CMMG products and don't have any first hand experience but maybe someone else will chime in. Basically you take a couple thousandths off the rear rib area of the mag to loosen the fit. |
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There are 2 tabs on the rear of the magazines. Instructions are normally included with your purchase. Those tabs must be
filed to fit your lower.. Also, it's recommended that the mags be loaded with fewer rounds when new and worked up to about 20 total for best function... See CMMG's Industry Forum as mentioned.. Your bolt hold open can be adjusted by a set screw. Also see the CMMG Industry Forum for instructions. You've already broken the conversion in some. Unless you got the optional Stainless Steel conversion, it may take some more rounds before things settle in... It'll all work out, just take a little time and read about it.... Good Luck, Dave |
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Thanks Guys,
I did read through that one piece of paper that came with the upper but looked right past the part about filing the tabs to fit. I saw something in there about how these steps are done at the factory if you buy a complete upper and pretty much quit paying attention after that. 
Just finished doing a little filing and both mags fit great now. Looks like I still need to do that 45 degree filing on the top of the mag though. So, I should be able to adjust the hold open to keep the bolt from locking back at times when it shouldn't? |
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Quoted:
iScream, I believe that the 45 degree filing you're referring to is only if you are converting Black Dog mags to use the BHOA. Thanks. I was just looking at both the mags and it looks like they already have a 45 degree chamfer. I also forgot to mention in my last reply that I do have the stainless bolt upgrade. |
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Took it back out for a while this afternoon. Ran another 100 CCI Mini Mags through it and 70 rounds of Federal bulk. Had the bolt lock back on me mid mag one time and one failure to feed. I did adjust the BHOA a bit in between so I'll hold off on any judgement until I get some more rounds through it. Maybe I spoke too soon on the accuracy thing though. I was shooting at 50 yards today instead of 25 like yesterday and the grouping wasn't very impressive. I don't know what I should expect though since the only thing I have to compare it against is my hopped up 10/22 with a bull barrel and VQ trigger group. That Ruger easily groups less than 1" at 50 yards and I was at about 4" with this CMMG upper.
-Chris |
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Quoted:
Which ammo FTF fed or cci ? The bulk pack may be your problem. It was the CCI, which is what gives me less than 1" in the Ruger. The Federal stuff was slightly worse than the CCI. I was shooting with the hand guard resting on a padded wooden block and it felt pretty steady. I was switching back and forth between the rimfire AR and one of my regular .223 AR's, shooting on the same rest from the same chair. I was grouping about 2" with that gun. The guns have identical lowers and the triggers feel The center fire gun has a decent scope on it and I had it set to about 6X magnification. The Evolution has a Primary Arms M4 clone one it with no magnification. Maybe that and the weight of the bull barrel on the other AR was helping me hold it more steady. They have a couple ransom style rests at the range. Next time I'll grab one of those and try to take myself out of the equation. I'm not overly worried about it. I got the rimfire gun for cheep practice shooting from the shoulder, not off a bench. It will take a hell of a lot of practice that way before I can get any kind of decent groups but I was expecting a little better. Not ready to pass judgement just yet though. -Chris ETA: I didn't read your question well obviously. The FTF was with the Federal, I think. |
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Cheep bulk ammo tends to FTF more than the more expensive brands.
But like I said do not use Remington golden bullets they are worse than useless in AR conversions you will end up throwing or giving them away. The gun shop I used to go to in the UK before I moved to the US used to do sale or return on them because they were so bad! |
| I have a hard time shooting any red dot accurately compared to a scope. The red dots generally are larger than the targets I shoot and the size of the dot is not as precise as a cross hair. The best I can do is make a circle target which is the approximate size of the red dot at the given range. I then can super impose the red dot on my black circle target and do a little better. Red dots are known for speed not the best indication of a rifles true accuracy. |
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