CASE WEIGHING
Bill Preuss
being used what or how much is the deviation when weighing the cases?
1 grain, 2 grains, a half a grain, etc? I am currently using Federal
brass which comes in at about 173 grains and using plus or minus .5
grain. Is this OK?
Thanks,
Bill Preuss
Bart Bobbitt
Accurate Ammo. A 5-grain spread in .308 Win. cases will permit groups
of 0.5 MOA at 600 yards and 1 MOA at 1000 yards, providing the rifle
is built properly with the right parts. And even brand new, never
fired cases can do and have done this.
Getting a uniform lot of primers is probably the most important thing
for accuracy with the .308 Win., especially for ranges of 300 yards or
greater. And using milder primers is probably a very close second place
issue. Then using a compatible powder (4064 for 160gr.+ bullets, 4895 for
lighter ones) completes the issue. As long as velocity spread is less
than 25 fps, that'll do fine.
More important than case weight spread is case wall thickness uniformity.
But both Winchester and Federal cases are pretty good in this regard.
Military cases are pretty bad in this department.
So, you can sort cases by weight if you want to. But I think you'll be
hard pressed to detect changes in accuracy caused by case weight spread
alone. Too many other things exist that'll cause bigger differences.
You'll probably get 1/20th MOA improvement in groups at less than 600
yards, 1/10th MOA improvement at 1000 yards.
BB
Randy Howard
#More important than case weight spread is case wall thickness uniformity.
#But both Winchester and Federal cases are pretty good in this regard.
#Military cases are pretty bad in this department.
I notice that one of the "big names", i.e. Remington, isn't listed here.
Is this because they aren't consistent in wall thickness, or because
you haven't tried it? Just curious because I have a lot of Remington
brass. If it's significantly less uniform than Winchester or Federal,
I won't bother working with it too much.
--
Randy Howard (j...@mustang.us.dell.com) Dell Computer Corp.
Illegal != Unavailable
Bart Bobbit
: I notice that one of the "big names", i.e. Remington, isn't listed here.
: Is this because they aren't consistent in wall thickness, or because
: you haven't tried it?
Regular Remington factory brass has been a little less uniform than
the others. But the Remington BR brass seems to be pretty good.
It's been a few years since I measured regular Rem. brass; it may be
better these days.
The reason why I didn't mention the Rem. BR brass is because I forgot to.
It's excellent for use at 300 yards or less. But loads for use at 600
yards and greater just don't seem to do as well as those using large
primers.
Any brass that's uniform is great; don't matter what's stamped on its
head.
BB
Emil Albertini
EA>
EA>More important than case weight spread is case wall thickness uniformity.
EA>But both Winchester and Federal cases are pretty good in this regard.
EA>Military cases are pretty bad in this department.
EA>
EA>BB
Bart,
How do military national match cases stack up against those you
cited, here, i.e., Winchester, Federal and (vanilla) military?
//emil
Bart Bobbit
: How do military national match cases stack up against those you
: cited, here, i.e., Winchester, Federal and (vanilla) military?
Poorly.
Military cases are among those at the bad end of the spectrum. Even the
match cases are pretty bad. In measuring all types of cases for uniformity
in weight, wall/neck thickness, primer pocket and flash hole dimensions,
I have never felt bad about leaving thousands of new, once-fired military
match cases lay on the range for others to pick up. That was when I was
in the service; after all, civilians paid for those cases and they just
might want to have them back.
The most uniform of all the military match cases I've measured were those
used in the M118 7.62 NATO National Match lot in 1967. Not surprizing, as
that LC 67 NM lot was also the most accurate M118 ammo ever made. I've
measured several M852 cases for uniformity; they're about the same as the
M118 cases.
Remember that military match ammo accuracy specifications are quite a ways
away from what good handloads can produce. Any ammo lot that produces
test groups at 600 yards of less than about 12 inches is acceptable. A few
lots get down to about the 6-inch range. Decent commercial cases can
produce groups at 600 yards of about 2 inches.
BB