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Posted: 6/7/2011 7:17:22 PM EDT
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I did not want to hijack a thread, but wanted to ask this question in response to an answer in another thread.
The BHOA shouldn't need to be modified other than if it is too tight in the upper.
I just received a new upper from CMMG. SS bolt and collar, etc. ( I love this thing !!! but more on that later !! ) I also got the BHOA mags and adapter. I am having some minor trouble figuring out how to adjust it. I can get it to lock open the bolt when firing in the field, but if cycling manually, it only locks open about half the time. I am assuming I do not have it adjusted properly, but cannot tell from the instructions what to do different. When I read that the BHOA should not be too tight in the upper, I thought I may be on to something. My BHOA adapter is pretty snug in the upper. The little lifter thingy (sorry I don't know the exact name of the piece that catches the bolt) is pretty loose and free moving. The bolt catch / release on the AR lower moves just as it should. I have it adjusted to be just below the bolt when cycling, but not binding the bolt. On exam, it appears as if the springs in the magazines are not strong enough to push the catch up in order to capture the bolt. I have cleaned and lubed everything. No luck. I guess this here is my question: should the BHOA move in the upper freely? mine takes a fair amount of force to remove. Not to the point of grunting to remove it, but it does not fall out on it's own either. I am probably going to call CMMG tomorrow, but I might as well ask here also. Thanks for any help, JKM |
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You should shoot the BHOA to see if there is a problem. In some cases the
Bolt Latch Spring may be a little strong for good operation as mentioned. If you feel that the BHOA itself is too tight in your upper / lower then calling CMMG is a good idea.. Good Luck, Dave S / Spec |
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If the BHOA frame is too tight in the upper, when the upper is opened, the BHOA frame will be stuck in the upper instead of sitting in the lower as it should. You can simply sand the sides of the frame for fit.
It sounds like the bolt catch spring is too strong for the mag spring to overcome. New mags may take some time to wear in. You can put an o-ring over the BC paddle to relieve some spring tension or you can clip one or two coils off the BC spring. If using the lower for 5.56 also, do not cut more than 2 coils off. I checked 5 different lowers from various manufacturers when we started testing. Bolt catch spring hole depths varied and accounts for the different spring tensions. Dave N |
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Quoted:
If the BHOA frame is too tight in the upper, when the upper is opened, the BHOA frame will be stuck in the upper instead of sitting in the lower as it should. You can simply sand the sides of the frame for fit. It sounds like the bolt catch spring is too strong for the mag spring to overcome. New mags may take some time to wear in. You can put an o-ring over the BC paddle to relieve some spring tension or you can clip one or two coils off the BC spring. If using the lower for 5.56 also, do not cut more than 2 coils off. I checked 5 different lowers from various manufacturers when we started testing. Bolt catch spring hole depths varied and accounts for the different spring tensions. Dave N I was thinking a few weeks ago it might be interesting to have a running list of lowers with and without issues regarding the BHOA. Personally I have two Spikes lowers where the BHOA worked without issue. I also have two Aero Precision lowers and a Plum Crazy lower where the BHOA didn't work without trimming the bolt catch spring or installing an O-ring around the bolt catch paddle. |
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Quoted:
You should shoot the BHOA to see if there is a problem. In some cases the Bolt Latch Spring may be a little strong for good operation as mentioned. If you feel that the BHOA itself is too tight in your upper / lower then calling CMMG is a good idea.. Good Luck, Dave S / Spec Thanks for the info. It does seem to function fine when firing, but on manual operation, it works only about 1/2 the time. I may be calling them to get their input as well. Thanks again. JKM |
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Quoted:
If the BHOA frame is too tight in the upper, when the upper is opened, the BHOA frame will be stuck in the upper instead of sitting in the lower as it should. You can simply sand the sides of the frame for fit. .. That is exactly what is happening. And I am guessing it should not. I'll try to call CMMG first, then take the sandpaper to it. It sounds like the bolt catch spring is too strong for the mag spring to overcome. New mags may take some time to wear in. You can put an o-ring over the BC paddle to relieve some spring tension or you can clip one or two coils off the BC spring. Yup, new mags. I may give it a bit more time. I only have about 200 rounds through this thing to begin with (4 mags, 2 reloads each). I may just need to b e more patient. I tend to shoot 50 to 100 rounds then clean. I do this for the first 300-500 rounds. So, I'm still in the break in phase. Also, could you show a picture of the O-ring fix. I cannot picture it in my head. I probably won't clip any springs any time soon because this is my lower for my 5.56. It runs without any hiccups. I don't want to mess that up at all. If using the lower for 5.56 also, do not cut more than 2 coils off. I checked 5 different lowers from various manufacturers when we started testing. Bolt catch spring hole depths varied and accounts for the different spring tensions. Dave N Thanks again for all the help from everyone. This is a great forum for information. JKM |
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