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Posted: 12/7/2010 6:58:46 PM EDT
| I have a used BCM BCG with around 800-1000 round through it. I'm purchasing a brand new BCM upper shortly. Can I use this BCG in the upper safely or should I put a new bolt in it? I don't want to buy headspace gauges and I don't know anybody locally to check it for me. |
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Never heard of a BCM upper having headspace issues. Your carrier is not an issue and your bolt is barely broke in. I'd shot it without much concern. I trust BCM workmanship. But then that's just me. If you have serious concerns call BCM or find a good gunsmith. To find a local gunsmith go to the hometown section.
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| I wouldn't call a bolt with 1k rounds on it "barely broken in" and it's not the BCM upper I'm worried about it's putting a used bolt into a new upper ... this is never a good idea. I wouldn't do it without checking the head space first but even then I would still prefer to have a new bolt .... your carrier is fine. Think about it ... you are using something inches from your face that functions using controlled explosions .... why take a chance of a KB and injury over a $50.00 part? |
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Ive been doing some reading since I saw your question. This is what i concluded from my brief research.
If the used bolt you have was in spec when you got it and the new barrel and barrel extension is in spec then I highly doubt 1000 rounds on the bolt would be enough to make your new set up have too much headspace. If your last upper shot safely with the bolt you will be using then I wouldn't worry about it. If you have a problem with the new upper then it would most likely Be the barrel and barrel extension being out of spec that's causing the problem. If a used bolt Is worn out then the headspace would be too large. A little too much headspace is much less of a problem than too little headspace. |
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Quoted:
Ive been doing some reading since I saw your question. This is what i concluded from my brief research. If the used bolt you have was in spec when you got it and the new barrel and barrel extension is in spec then I highly doubt 1000 rounds on the bolt would be enough to make your new set up have too much headspace. If your last upper shot safely with the bolt you will be using then I wouldn't worry about it. If you have a problem with the new upper then it would most likely Be the barrel and barrel extension being out of spec that's causing the problem. If a used bolt Is worn out then the headspace would be too large. A little too much headspace is much less of a problem than too little headspace. Any combination of parts (new to new/used to used/ new to used etc etc) can have issues. There is thing called tolerance stacking ... as in not every bolt on the market touted as "mil spec" is going to be exactly the same as the next ... one could be -.001" and the next could be +.001" then add to that an extension that might be +/- .001" then add in used part wear and you can have some serious issues .. maybe even a KB. Thus the reason I head space all my rifle to bolt match ups now .... cost me $60-$70 for a set of gauges .... small price to pay when you might be talking mine or someone else's vision or life. |
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Here's my advice. If your the type person who would check headspace on a new bolt and a new barrel/upper that you purchased separately then you should check headspace with a used bolt in a new upper. But the fact that your bolt has 1000 rounds on it is a non issue. Your bolt was already out of spec or on the very very verge of being our of spec when new if it only has 1000 rounds and it's out of spec now.
I wouldn't buy a new bolt. If you buy anything buy a set of go/no go gauges. But based on everything i have been reading, I would just put it in And shoot it. Just my 2 cents. |
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As a machinist, I cant understand why some just dont understand...
Think of a hole, and a ball If you have a hole thats undersize and a ball thats oversize, it is a nogo If you have a hole thats oversize and a ball thats undersize and drops in. Im not sure the actual mil-spec measurements, but if its say +/- .002, it could be off up to, but no more that .004 (.002 x two parts= .004... again, in spec but a no go. Hope this helps. With a used bolt in a new barrel, its more than likely going to be on the loose side. |
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