308 Win Chamber length

[Shane Lindsey]

Greetings,

Have a Rem 700 308 Win with a Carbon Six barrel. I had Carbon Six chamber up for me.

First time measuring the chamber length with the Sinclair tool. Have never measured any before and have always trimmed to 2.005", but wanted to know on this one.

Length came out to be 2.051" average. This is quite a bit more than my manual says at 2.015".

Is this pretty normal? Anyone second guess the gauge and do a cast to find it was way off?
I always trim during case prep, typically after every firing, but have heard others do not. I always exceed 2.015" on fired brass so assumed this was always going to be a requirement.

Thanks for any assistance,
Shane

 

[shortgrass]

It sounds to me like your 'gauging' is including the chamfer at the transition of the chamber to the free bore. The measurement from the 3/8" diameter at the datum to the bolt face is the critical measurement. That is where true head space is measured, and measured most accurately with hardened steel head space gauges, the GO and the NO-GO.

 

[ShtrRdy]

The Sinclair tool you're using -- is it like a plug that you put into the case instead of a bullet? Then chamber the case so that the plug is pushed in?

 

[Shane Lindsey]

The Sinclair tool you're using -- is it like a plug that you put into the case instead of a bullet? Then chamber the case so that the plug is pushed in?

Yes it is. The reading I am getting is just a pretty big difference from book specs.

What Shortgrass stated about reading into the chamfer makes sense. You lost me with the headspace bit though. I am trying to determine what minimum length I need to trim the brass to.

 

[shortgrass]

Trim your .308 Win brass to 2.005"-2.010" and be happy! You are "creating" a problem that doesn't exist. You are worried about nothing!

 

[ShtrRdy]

I just took a look at the SAAMI chamber drawing and it looks like 2.05 is the nominal chamber length from the beach face to the end of the neck. A maximum length would add 0.015" to that. So I'd say you're measurment is the correct number.