Posted: 5/4/2011 8:27:24 PM EDT
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I just received my brand new CMMG .22 Evolution dedicated upper - Yeah!
I ordered it with every option available. I have been working this thing for three hours now and have read every manual CMMG has published but I cannot for the life of me get the BHOA to work. Any help or tips would be appreciated... Thanks - 
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First, make sure you have adjusted your mags with the tabs on the back for a fit to the mag well. Not too tight.
Second, make sure the BHOA is not pinched in the upper. The upper should not have any problem closing or opening. If it does, the BHOA will probably be stuck in the upper. Sand the sides of the frame for fit. The biggest issue I have run into with the BHOA is the bolt catch spring tension. The mag spring has to over come this. Try to manually lock the bolt back as you would on a standard AR with the bolt catch. If it works, it is probably the bc spring. You can slip an )-ring over the paddle to relieve tension or , I cut 1-2 coils off the spring. If it doesn't lock manually, try adjusting the set screw on the underside of the BHOA clockwise a little at a time. Too much and the bolt will not close. I adjust it in until the bolt barely starts to drag, then back off 1/2 turn. Dave N |
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Quoted:
First, make sure you have adjusted your mags with the tabs on the back for a fit to the mag well. Not too tight. Done. Second, make sure the BHOA is not pinched in the upper. The upper should not have any problem closing or opening. If it does, the BHOA will probably be stuck in the upper. Sand the sides of the frame for fit. Done, fits well. The biggest issue I have run into with the BHOA is the bolt catch spring tension. The mag spring has to over come this. Try to manually lock the bolt back as you would on a standard AR with the bolt catch. That works as it should. If it works, it is probably the bc spring. You can slip an )-ring over the paddle to relieve tension or , I cut 1-2 coils off the spring. I'll give that a try. If it doesn't lock manually, try adjusting the set screw on the underside of the BHOA clockwise a little at a time. Too much and the bolt will not close. I adjust it in until the bolt barely starts to drag, then back off 1/2 turn. That's about how I have it adjusted. Dave N I'm thinking you are correct about the mag spring not overcoming the bolt catch spring. In fact if I push the follower down into the magazine I have to bang on the magazine in order to get the follower to slide back to the top. If I loosen the screws that hold the magazine together the follower seems to slide freely. I'll spend a little more time working the the bolt catch spring and magazine spring issue.... Thanks for your input Dave - |
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With a symptom of "In fact if I push the follower down into the magazine I have to bang on the magazine in order to get the follower to slide back to the top.", I would suspect the channel the follower sits in has some defects.
The screws holes in my mag were slightly deformed from pressure, and caused bulges. The bulges didn't affect my original follower, but the new one snagged on them. Might be worth popping the mag apart and verifying nothing is causing a follower hangup. (I have my mag looking pretty functional, need to tackle my bolt next. Removing metal always makes me uncomfortable.) Keith |
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Welp!
I'm starting to get frustrated!! I can't seem to get the BHOA to work at all, and on top of that it seems that if I slow release the bolt it stalls about a quarter inch from battery even without a magazine up the well... I'm gonna scratch my head for a while - then - I don't know....  
Thanks to all who tried to help.... 
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Quoted:
Show us a close photo of the BHOA inserted in the lower, without the upper. Then show us a close photo of the BCG's bottom. Ted Ah, the BCG might be the problem.... The BHOA fit and adjustment seems fine. The BHOA instructions say that all Uppers shipped with the BHOA (my upper was ordered with the BHOA) don't need any modifications as they were done at the factory. It looks like the rear modification was done but the forward end of the bolt still has a radius. I'll go to work on that radius today and see how it goes! Turns out the bolt not going into full battery wasn't a problem at all - just a brain fart by me.... 
I'm going to get this thing running like a Swiss watch yet..... 
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It's all working fine now!!! Woo Hoo!!! 
Turns out after I got to really looking at it that the BCG mods were indeed all done correctly - no problem there. I went back and revisited all your guys suggestions. I disassembled the magazine and smoothed up the follower with a bit of emery cloth then applied a spritz of silicon spray then worked the follower up and down the channel for a bit. I also clipped another coil off the Bolt Catch spring. I also cleaned and carefully lubed everything. Working those issues seems to have solved the problem. She's working like champ now!!! I want to thank you all for your help and suggestions! 
~Terry~ 
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