Posted: 12/8/2011 6:16:23 PM EDT
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I'm not sure if I should post this here or in the .22 rimfire section. I'll try here because it is a CMMG product.
I've searched the web and this forum and cannot find a good answer to my question. First off, this is a great rifle. I love this gun. I just got a dedicated .22 upper from CMMG last spring. I have about 1,000 rounds through it. I have been using the BHOA and the grey BHOA magazines. When I am firing the rifle, the bolt will lock back about 75% of the time. But if I manually cycle the bolt, it is more like 10% of the time. The bolt catch / release works fine if used manually. Here is the question part: The BHOA that sits in the mag well of the rifle is pretty tight fitting in the upper. When I break it down, I have to tug pretty hard on it to get it out of the upper receiver. Should it be this tight, or should it be a bit looser fitting? If it should be a looser fit, can I just take sandpaper to it to size it down a bit ? Any information would be appreciated. Thanks, JKM |
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It should not hang in the upper. That can cause binding. Sand a little off the sides of the frame.
Another thing to be aware of is the bolt catch spring tension. Some are stiffer than others. I have had to cut 1 or 2 coils off the bolt catch spring of two lowers for good BHOA operation. To adjust the BHOA, I install it. Turn the rifle to where the mag well is up. Insert the allen wrench into the BHOA hex screw. While moving the bolt slowly back and forth, adjust the screw in. When the bolt starts to drag, back the screw off 1/2 turn. Dave N |
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Thanks Dave.
So let me get this straight. 1. BHOA should not bind, but should not fall out either. Sand sides to achieve proper friction fit. 2. To adjust the BHOA, Install, then turn rifle upside down. The little bolt catch thingy on the BHOA will fall with the force of gravity until it hits the bolt. I advance the little set screw until there is enough pressure on the little bolt catch thingy to cause a bit of discernible drag. Then back off about 1/2 turn. 3. Bolt release spring. The pressure can be reduced by clipping coils. Next question, how does this (i.e clipping coils) affect function when lower is used for 5.56 upper ? Thanks again for your help. JKM |
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I have clipped a coil off the BHO latch on one lower and it has not affected operation of the BHO latch when using 5.56 magazines. Main thing is to not get carried away. Just one coil fixed my rifle.
BTW, when I was working with it I punched out the roll pin for the latch. I clipped the coil then put the parts back in the rifle. I secured them with a small punch while I tested the action to make sure the BHOA now worked. Once I was confident everything was good only then did I put the roll pin back in. You just have to find something the same size (or ever so slightly smaller) than that roll pin that you can stick in to hold everything in place for the test phase. Just a little off that spring can make a big difference. |
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Quoted:
I have clipped a coil off the BHO latch on one lower and it has not affected operation of the BHO latch when using 5.56 magazines. Main thing is to not get carried away. Just one coil fixed my rifle. BTW, when I was working with it I punched out the roll pin for the latch. I clipped the coil then put the parts back in the rifle. I secured them with a small punch while I tested the action to make sure the BHOA now worked. Once I was confident everything was good only then did I put the roll pin back in. You just have to find something the same size (or ever so slightly smaller) than that roll pin that you can stick in to hold everything in place for the test phase. Just a little off that spring can make a big difference. That helps a lot. I was wondering about how to test this without putting it all back together again, thanks. It looks and sounds like this is probably my issue. The follower in the magazine is not pushing the catch up far enough to catch the bolt. It hangs just a bit. Even when really really clean and adequately lubed. But if I give it a bit of a nudge on the bolt release, it does just fine. I think I'll concentrate my efforts on the spring. I'll let y'all know how it turns out. JKM |
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Quoted:
why does my bolt close when inserting 2nd gen bhoa mag ? During courses - dont tell me to insert gently under stress. will new mags prevent this? Without seeing this rifle this is only a guess. It might be the BHOA is just barely catching the bolt and when you jar the rifle putting in the next mag it pops loose. Just for sake of it, try pushing the BOHA up with your finger (actually I use the eraser end of a pencil as its long enough to fit up through the mag well) so you know its up far enough. Then try inserting the mag and see if the bolt come "unlatched" and moves forward. Also, check the bottom of the bolt where the latch catches it and make sure you have a good surface to latch up against. Again, it sounds like the BHOA is not getting a good "bite" on that bolt and lets it go too easily. Just stuff to look at. BTW, how stiff is your bolt latch spring? Could it be its not letting the BHOA come up far enough? I had this problem on one lower. It was hit or miss just depending on how you were holding your mouth when you stuck the mag in or something. A slightly softer spring fixed that one too. But, all these lowers are different so you may have to do some experimentation to get it to work on your firearm. |
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If it is hanging in the upper when you crack the upper open, sand the upper bevelled part of the BHOA frame length wise. You may need to knock a little off the sides. Just take your time. You don't want it sloppy loose. I actually broke one recently because a new upper/lower had a tight fit. I got in a hurry.
It happens. Different tolerances even from the same manufacturer is the problem. This happened with a CMMG upper and lower. Dave N |