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Posted: 4/16/2010 10:13:11 PM EDT
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A while back I posted a thread about my rifle's bolt staying locked back when there was still plenty of ammo in the magazine.
Tonight I examined my gun next to my buddy's gun and I think I found the issue. I believe my lower receiver is out of spec. There is too much slop between the bolt catch lever and the receiver. I took some various measurements from the two guns and the most telling is the fact that I can fit a .025" feeler gauge between the bolt catch and the lower (where the roll pin is). And my buddy's gun I can fit a .008" feeler gauge in the same area. I took out both bolt catch's and measured them with calipers and they match up....so that leads me to believe it's a sloppy lower receiver. 
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You have lost me a tad,
Is it that your bolt catch tab is protruding too far forward into the mag, and the rim of the case is what is causing it to trip? Or is the problem that your mags are rattling around in the well like a BB in a box care, allowing the mag to angle/move back and cause the above problem? When all else fails, go to the main page here at the site (ar15.com) and on the bottom left hand side you will can download the blue prints for the lower to confirm if you lower is out of spec or not. If you do find it to be out of spec, then get hold of the manufacture to have him warranty the receiver out to one in spec. |
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A picture is worth a 1000. It is the channel (or groove) the bolt catch sits in, it's too wide.
http://img.photobucket.com/albums/v314/SilverSurfer77/Guns/CopyofDSCF2889.jpg |
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I knew that was the tolerance/play you were talking about. I don't think that is the problem. Did you assemble it? Can you check to see if the correct spring is installed? How much gap is there between the bolt lugs and the catch when the catch is not engaged?
ps your serial number is showing ....you could block it out to be safe |
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if you do take out the roll pin to check the spring make sure you check for any burrs or anything else that could bind things up. Burrs in the spring chanel, burrs on the roll pin, deformed roll pin. Also check the depth of the hole for the spring and detent.
With the correct spring and detent the top of the detent should be about flush with the surface of the lower. RRA will ship parts out USPS so you don't pay a fortune on shipping **Although, what you originally said may be the problem if that extra space is letting the rounds in the mag contact the bolt catch and push it up***. I have an old olympic....i took the catch out, measured the slot for you, it is 0.16 inch on mine |
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Thanks to all that answered! Here are my replies...
tommyt Did you assemble it? Can you check to see if the correct spring is installed? How much gap is there between the bolt lugs and the catch when the catch is not engaged? > No I did not assemble it. This is the way it came from Olympic Arms factory. This is my first AR, not sure how to tell if this is the correct spring. Not sure what gap you are referring to?...I can fit a .025" feeler gauge between the catch and the roll pin lugs. ps your serial number is showing ....you could block it out to be safe > I changed the pic...but what could possibly happen if someone used my serial number maliciously? if you do take out the roll pin to check the spring make sure you check for any burrs or anything else that could bind things up. Burrs in the spring chanel, burrs on the roll pin, deformed roll pin. Also check the depth of the hole for the spring and detent. > everything looks good and clean. I can measure the hole depth, do you know how deep it is supposed to be? With the correct spring and detent the top of the detent should be about flush with the surface of the lower. > I think it is, but I will 2x check. RRA will ship parts out USPS so you don't pay a fortune on shipping > Kinda wish this was an RRA and not an Oly! **Although, what you originally said may be the problem if that extra space is letting the rounds in the mag contact the bolt catch and push it up***. > I will see if I can manually produce this condition in the garage. I have an old olympic....i took the catch out, measured the slot for you, it is 0.16 inch on mine > My slot measures .157"-1.60" (this is on the inside of the receiver). On the outside where the roll pin lugs are it measures a whopping .170"-.172"! powdershots small nylon washer to the rear of latch ftw > I was actually thinking the same thing! zebcoboy I would suspect a weak spring or maybe the wrong spring. There is a detent that is supposed to cap the spring. Is it missing? Any parts left over after build? > Factory build. The cap is there. Not sure how to tell if this is the proper spring or weak spring. I could buy a new one and put it in anyway, wouldn't hurt. RangeWarrior you might also want to check that the buffer tube is straight. > Is this in regards to the original problem or the bolt locking back with rounds in the mag? I removed the buffer tube a few weeks ago and re-installed it, and the bolt still locks back. Unless the entire receiver is bent or the buffer tube itself, I don't see how this could be a problem. |
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