Little Bit or Lotta Bit: 23 & 56 Headspacing

YeeHaa

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Many to a Great majority of use are fully aware that there are differences with the 223 & 5.56 cartridges.

Recently I was checking the Headspace on a barrel and became rather alarmed when it came out to 1.4686.

No Go for the 223 cartridge is 1.466.

I started to double ck stuff and noticed the barrel being Stamped 5.56 1:8, OK.
While I've ck HS on 56 barrels before I did not recall one being this, loose?

Looked the specs up for 5.56 Headspacing and determined it does fall within spec.

Anyway, I came across a simple HS graphic and thought to post it for others.

23 ~ 56 Headspace_B.jpg
 
Last edited:
Yup... USGI headspace values are always more generous than SAAMI. Here are the .308WIN/7.62x51mm specs for comparison.

SAAMI .308WIN
GO: 1.630 in.
NO-GO: 1.634 in.
FIELD: 1.638 in.

7.62x51mm
GO: 1.6355 in.
NO-GO: 1.638 in.
FIELD: 1.6445 in.
 
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