From: khays@sequent.com (Kirk Hays)
Newsgroups: rec.guns
Subject: Re: .308 vs 30-.06
Date: 5 Nov 1998 22:06:01 -0500

In article <077ab34400304b8UPSMOT07@msn.com>,
Danny K Thompson <dkthomps@msn.com> wrote:
#I have a question about the same thing. I looked at ballistics for Remington
#factory.
#
#308 Win - 165gr - SPBT - muzzle 2700fps - 500yds 1773fps
#zeroed at 200 yards. 500 yard drop -50.6
#
#30-06 Springfield - 165gr - SPBT - muzzle 2800fps - 500yds 1852fps
#zeroed at 200 yards. 500 yard drop -46.6
#
#I am a handgun shooter only so maybe I am missing something, but these
#numbers don't look a lot different to me. Is there a lot of difference
#between these two cartridges?

Some folks get all wrapped around the axle on this difference, but the
80 fps difference in the factory data is less than the difference that
can be observed firing one lot of ammo in two different rifles.

As an example, I have access to two M1A rifles in .308 Win, with
serial numbers 14 rifles apart.  The same factory ammo, fired in these
two otherwise apparently identical rifles, consistantly averages
150fps difference in velocity.  There is no quantifiable reason for
this - I've measured headspace, slugged the bores, measured the gas
ports, weighed all operating parts, and they're all the same within my
measurement limits.  We went to far as to switch all moving parts
(bolt (check headspace!), oprod, oprod spring, trigger groups) (kids,
don't do this at home), and the difference tracked the
receiver/barrel.

Frankly, I'm down to blaming it on the micro-finish of the bores.

--
Kirk Hays
[I don't speak for Sequent.]