In extensive test with .45 Colt, I was getting spreads as
great as 125 fps between shots. Trying to locate the reason
for the variation, I shot a set of 6 shots carefully tapping the
gun with muzzle in the air, and gently lowering the gun to level
and firing off the shots. Then, I did the exact opposite, pointing
the gun to the ground, tapping chamber, and raising to level to
take the shots. Here are the surprising results.
Using 10 grains* of Unique (7 1/2" bbl)(only in Ruger and T/C) with a
250 grain RNFP lead bullet, pointing in the air to put powder
rearward next to the primer, I got 1024 fps. The spread between
the shots was 47 fps. Then shooting a set pointing to the ground
between each shot, I got 848 fps. The spread between shots was
78 fps. The average difference between strings from powder in
rear of case and powder in front of case was 176 fps.
Using 10 grains* of Unique (7 1/2" bbl)(only in Ruger and T/C) with a
255 grain SWC lead bullet, pointing in the air to put powder
rearward next to the primer, I got 1007 fps. The spread between
the shots was 34 fps. Then shooting a set pointing to the ground
between each shot, I got 864 fps. The spread between shots was
70 fps. The average difference between strings from powder in
rear of case and powder in front of case was 143 fps.
MASTER Commercial Ammo using 260 grain Jacketed Hollow Point
bullet (powder unknown)(7 1/2" bbl) exhibited this performance:
Using 10 grains* of Unique (4 5/8" bbl)(only in Ruger and T/C) with a
250 grain Rainier FP bullet, pointing in the air to put powder
rearward next to the primer, I got 981 fps. The spread between
the shots was 40 fps. Then shooting a set pointing to the ground
between each shot, I got 770 fps. The spread between shots was
118 fps. The average difference between strings from powder in
rear of case and powder in front of case was 211 fps.
I believe some valid conclusions can be made here. If you point
your gun skyward between shots, you will get higher velocities
and a more consistent spread of speeds. Pointing the gun down
and allowing powder to rest away from the primer and more next
to the bullet, causes lower velocities and greater spread of
speeds.
[7/20/96]
* This EXCEEDS the MAXIMUM load for Colt .45 for old and/or
standard guns. Use ONLY in Ruger and T/C and modern rifles.
Pointing in the air to put powder
rearward next to the primer, I got 857 fps. The spread between
the shots was 29 fps. Then shooting a set pointing to the ground
between each shot, I got 742 fps. The spread between shots was
64 fps. The average difference between strings from powder in
rear of case and powder in front of case was 115 fps.
This would speak to using a powder that more nearly fills the
case to minimize differences in powder position in a large case
like the .45 colt. Certainly a load that was nearly a compressed
load or a slightly compressed load, should be the most consistent
you could shoot. I intend to further investigate this issue and
find powders that have greater volumn to see how much this
problem can be minimized. [6/23/96]
-----------------------------------------
230 grain Round Nose LEAD
(Experiment with A5744 powder)
AA5744 17.0 gr. 836 fps (powder pointing UP)
(Hi=877.7 Lo=803.0 Spread=74.7 fps)
AA5744 17.0 gr. 771 fps (powder pointing DOWN)
(Hi=783.1 Lo=760.3 Spread=22.8 fps)
-----------------------------------------
250 grain LRNFP (Lead Round Nose, flat point)
AA5744 17.0 gr. 853 (Powder UP - see note)
(Hi=872.5 Lo=827.5 Spread=45 fps)
AA5744 17.0 gr. 802 (Powder DOWN - see note)
(Hi=809.2 Lo=792.6 Spread=16.6 fps)
-----------------------------------------
Accurate Arms powder #5744 is a much more "case position
insensitive" powder than others I have tried. I also used
No. 9 which is slower and takes about 15 grains for a good
Colt load, and it still showed about the same problems with
case position, but not to quite the same extent as the
faster powders. As of this time, this seems to be the
best I have found. I plan to try others in this test. [7/20/96]
