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Posted: 7/26/2016 7:18:21 AM EDT
[#1]
Quoted:
New 5.56 bolt. Long story short i found the bolt face depth is measuring .130. From what ive read it should be .124. Is there a MAX depth and will this affect my headspace ? I do not have gauges. Thanks guys . update, i took measurements from this link and got .146. https://www.ar15.com/forums/t_3_4/674621_Bolt_counterbore_specs.html&page=1&anc=bottom#bottom It should be between .120" and .127". The next question is what are you measuring with? I you aren't using a "C" Micrometer and a depth micrometer, you probably aren't getting an accurate measurement.* The question after that is does it pass the field gauge? ____________________________ * A really good set of digital calipers are +/- .001", a relativity cheap depth micrometer is good to +/- .00025" |
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Posted: 7/26/2016 4:39:13 PM EDT
[#2]
Width of lugs should = .278 +/- .002
Back of bolt lug to face of bolt recess should be .156 +/- .003, Or if you want to measure bolt face to recess, then .122" +/- .005. Note, the dimension that really mater is the lug widths, and the back of lugs to face recess (this creates the head spacing), since the front of lugs to bolt recess is really just to keep the lugs from slamming into the barrel face instead. So at .130, if the other specs are good, not really the end of the world if you are not ending up with major tag marks to the face of the barrel breach instead. 
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Posted: 7/26/2016 6:11:03 PM EDT
[#3]
bolt width is .277 minus face recess of .130 = .147 back of lugs to bolt face. The specs show .156-.003 so its off a little. Im getting a no-go gauge to see where im at on the headspace.
Quote HistoryQuoted:
Width of lugs should = .278 +/- .002 Back of bolt lug to face of bolt recess should be .156 +/- .003, Or if you want to measure bolt face to recess, then .122" +/- .005. Note, the dimension that really mater is the lug widths, and the back of lugs to face recess (this creates the head spacing), since the front of lugs to bolt recess is really just to keep the lugs from slamming into the barrel face instead. So at .130, if the other specs are good, not really the end of the world if you are not ending up with major tag marks to the face of the barrel breach instead. http://i1286.photobucket.com/albums/a601/AVIDavid1982/AR15_Bolt_zpsc8021783.png |
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Posted: 7/26/2016 6:52:33 PM EDT
[#4]
Yep, check the chamber with a no go gauge, and if it swallows it, then you know that the chamber was not reamed to mate with the bolt in question.
If it was, then that brings up a whole new ball game and if you need to replace the bolt at some point, then stuck either trying to find a matching bolt to the one you have, or having to mill a new bolt face recess back to match the current bolt in play instead |
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Posted: 7/26/2016 8:29:59 PM EDT
[#5]
Who's bolt is it? One of the problems is many companies won't even tell you where they get their bolts from.
I like to buy Continental Machine Tool, Lewis Machine & Tool or something from John Holliger or Steve Thompson. Brownell's will back their products as well. Bravo Company will usually tell you who's bolts they have in stock. Cheap is rarely good. |
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Posted: 7/27/2016 7:52:21 AM EDT
[#6]
Quote HistoryQuote HistoryQuoted:
Back of bolt lug to face of bolt recess should be .156 +/- .003. Note: The .156" dimension is not +/- .003, it is just minus .003. They can be .153" to .156", big Difference. Quoted:
Or if you want to measure bolt face to recess, then .122" +/- .005. That make this .122 +.005/-.002, Or, as stated above .127" to .120" |
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Posted: 7/31/2016 7:01:59 PM EDT
[#7]
Update, got a PTG NO-GO gauge and the offending bol/carrier combo closed easily on it. Two other bolts in the same carrier did not close. Ive asked the dealer for a refund and they accepted.
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