Re: Powder charge accuracy/long range
Bart Bobbitt posted May 28, 2005:
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Charge weight spread ain't all it's often cranked up to be. For
example, in 1991 when a half dozen of us were developing the load for
Sierra's then new 155-gr. .308 Palma bullet, we tried several powder
types. All charges were metered from our measures as that's how the
ammo would be loaded. Charge weight spread ranged from about 1/10th to
4/10ths of a grain. The powder that produced the most uniform muzzle
velocity and pressure (by tests at the HP White lab) was AA2520. But
it was also the worst for accuracy. IMR4895 had a 3/10ths grain charge
weight spread, average muzzle velocity and pressure spread AND produced
by far the best accuracy -sub 3-inches at 600 yards.
Consider the fact that virtually all primers cause a greater velocity
spread than a 2/10ths grain charge weight spread. And testing muzzle
velocity from a shoulder fired rifle is NOT a good thing to do because
two people will get different averages and spreads with the same
shooting gear just because they ain't holding the rifle the same way.
Reliable muzzle velocity data is only attained by shooting the rifle
from a machine rest on in absolute free-recoil (untouched by humans
during firing) from sand bags. A proper prone position is second best.
Hanging on to a double bagged centerfire rifle with one or both hands
so it won't recoil off the rest is not all that great for velocity
testing. There can be as much as 100 fps or more velocity difference
between two people shooting the same rifle and ammo.
Go figure...... </div></div>
I am thinking that my 12" groups at 500 yards will improve most with better recoil management.... But I am so desperate, I am weighting each charge