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Posted: 4/14/2012 6:14:10 PM EDT
| so I want to buy a used BCG how will this effect relating to a new barrel and headspacing with the lugs is it safe to buy a used BCG and use with a new barrel or should I buy new? |
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The headspacing of an AR is controlled by how the locking lugs of both the barrel extension and the bolt are machined. The carrier, by itself, really should not make any difference here. If your barrel extension and a new bolt are both machined to acceptable tolerances, the headspacing should be acceptable. |
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Quoted:
well im looking at a LMT bolt and carrier and have a PSA barrel assembly on the way that is new. do you guys think this would work? Edit: the BCG is used  Check it with a field gauge. 5.56 Field Gauge The used bolt is like anything used....LMT is good but does it have 100 rounds on it or 10, 000 rounds ? |
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Checking headspace is a basic safety measure.
Headspace is measured from the face of the bolt to a point in the chamber. Therefore a true headspace measurement can only be made with the bolt the barrel will be used with. Using a field gage only tells you that the weapon is or is not safe to fire. Use a SAAMI NoGo Gage. As long as the headspace checks out it should work. How long it will work???? |
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Quoted:
Using a field gage only tells you that the weapon is or is not safe to fire. Use a SAAMI NoGo Gage. That is after all what the OP is wanting to determine. Now if we had a bin full of bolts we might be able to find a perfect bolt that closes nicely on 1.465" gauge. I agree with the database here that simply says to ignore the GO - NO GO and FIELD wording on the gauges and instead note the measurement stamped on the gauge. The reason is that there are so many civilian and military gauges for this chamber, actual measurements are the only way to sort them out. These are the dimensions and associated gauges New Rifle Headspace: 1.4646" to 1.4706" SAMMI headspace gauges to use: 1.465" and 1.470" Unsafe Rifle Headspace: 1.4736" Use the Colt M16/AR15 Field Gauge: 1.4736" or, The US military gauge: 1.4730” Note: The Forster/SAAMI "No-Go" gauge measures 1.467" With a full rim civilian gauge the bolt must be stripped of ejector and extractor prior to the check. With a rebated rim military gauge the bolt can be left intact. |
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