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Straight Shooter
06-04-21, 06:38
Ive got an unused bolt that I was told was "too small to headspace".
Is there a way I could measure this myself with digital calipers?
If so, what are the specs Im looking for?
Clint
06-04-21, 08:56
Using a standard headspace gauge set...

Stick the bolt it in a barrel and check as normal...


ETA: it is not unusual for a 556 chamber to close on a 223 NOGO gauge (MIN +.003)

As long as it does NOT close on a 223 field (MIN +.006) or 556 max (MIN +.010), it should be good to go.
Straight Shooter
06-04-21, 09:32
Using a standard headspace gauge set...

Stick the bolt it in a barrel and check as normal...


ETA: it is not unusual for a 556 chamber to close on a 223 NOGO gauge (MIN +.003)

As long as it does NOT close on a 223 field (MIN +.006) or 556 max (MIN +.010), it should be good to go.

Thank you- what about measuring length, and lug size, or any other physical attribute of the bolt? Can a bolt be out of spec and still headspace?
markm
06-04-21, 09:36
Headspace gauge removes all doubt. Lug size could be off, but it's relative to the bolt face that touched the case head.
georgeib
06-04-21, 09:39
Thank you- what about measuring length, and lug size, or any other physical attribute of the bolt? Can a bolt be out of spec and still headspace?

Check out page 4 on this PDF: https://www.dropbox.com/s/hmaoqnf3ny3yvm4/M16%20BCG%20Drawing%20Set.pdf
Straight Shooter
06-04-21, 09:54
Headspace gauge removes all doubt. Lug size could be off, but it's relative to the bolt face that touched the case head.


Check out page 4 on this PDF: https://www.dropbox.com/s/hmaoqnf3ny3yvm4/M16%20BCG%20Drawing%20Set.pdf

Thank you both!
lysander
06-04-21, 18:57
Ive got an unused bolt that I was told was "too small to headspace".
Is there a way I could measure this myself with digital calipers?
If so, what are the specs Im looking for?
Locking length should be 0.156 -.003"

https://i.imgur.com/C1YWs24.png
Straight Shooter
06-05-21, 16:10
Locking length should be 0.156 -.003"

https://i.imgur.com/C1YWs24.png

I appreciate that lysander.
lysander
06-05-21, 21:43
I appreciate that lysander.
If you don't have one of these fancy machines, you can get a very good idea (+/- 0.001) with a accurate depth micrometer and a regular "C" mic, or a fair idea with a good set of calipers (+/- 0.005).

Just measure the overall length of the locking lugs and subtract the depth of the breech face.
Todd.K
06-05-21, 23:55
Headspace will be from the back of the lugs to the bolt face. So measure the length of the lugs, then subtract the depth of the bolt face. Compare that to other bolts you have.

I hope you understand the limitations of calipers. Easy to mess up depth measurements if you don’t keep it square.
Straight Shooter
06-06-21, 11:48
If you don't have one of these fancy machines, you can get a very good idea (+/- 0.001) with a accurate depth micrometer and a regular "C" mic, or a fair idea with a good set of calipers (+/- 0.005).

Just measure the overall length of the locking lugs and subtract the depth of the breech face.


Headspace will be from the back of the lugs to the bolt face. So measure the length of the lugs, then subtract the depth of the bolt face. Compare that to other bolts you have.

I hope you understand the limitations of calipers. Easy to mess up depth measurements if you don’t keep it square.

Very good info, again, thank yall.
10-4 on the calipers, Todd.