Gunsmithing Headspace Questions

[Brux]

A unfired factory case in 308 that has not been sized measures 1622 with a hornady headspace guage.If you fire that case and it measures 1630,does that mean your headspace is .008?

 

[bward]

Not necessarily. You should use a go gauge instead of factory brass.

 

[chipsfan]

A unfired factory case in 308 that has not been sized measures 1622 with a hornady headspace guage.If you fire that case and it measures 1630,does that mean your headspace is .008?

Also keep in mind SAAMI specs on ammo runs short, the chamber runs long. If I remember right, 1.630 is minimum for chamber, 1.640 is maximum. Clymer No go is 1.634, Manson go is 1.636. Clymer Field is 1.638. All from a .400" datum on the shoulder.

You can get a complete set of 308 headspace gauges, in .001" increments, from Brownells.

 

[Brux]

Not using brass as a go guage,but I have one chamber stretching new brass .008.In my opinion it should be .004 at the most.

 

[chipsfan]

Not using brass as a go guage,but I have one chamber stretching new brass .008.In my opinion it should be .004 at the most.

I don't know how accurate those Hornandy gauges are. I am .006" off on various go gauges using three different high quality calibers.

Did you take a look at SAMMI minimum for a 308 case? Is that 1.626"?

 

[Straight Shooter]

I have seen factory brass .010" short. It's also way undersized near the base and can cause even perfect chambers to have bellies in the brass. We do our part. I wish the brass makers would do theirs.

I have found a lot of the toys in the Sinclair catalog to simply be gadgets designed to separate old men from their money. The Hornady Headspace gauge is one of them.