Originally Posted by
BruceB
In yesterday's episode, I found that while my starting-load selection with 4320 was right where I expected it be for velocities and pressures with the different bullets, the loads did NOT perform at all well as the charges were increased.
I therefore loaded three different bullet types with three incrementally-decreasing charges of 4320. The boolits were 311672, 311291, and 311467. The charges (of 4320) were 34.0, 32.0, and 30.0 grains, decreased from that starting load of yesterday, which was 36.0 grains.. I fired them in order of weight with each bullet...that is, I shot the 311291 loads in order from 30 to 32 to 34 grains, hoping to see any changes in behavior that might arise. I did see them, too.... The same order-of-fire was used with the other designs,as well.
Beginning with 311467, the 180 Loverin, the first round fired with 30.0 grains was over FOUR INCHES left of the point of aim. The next nine rounds were right in the x- and ten-ring of the 50-yd pistol center that I'm using at 50 yards (but folded in half to create a black semi-circle aiming mark). Velocity was 1816 fps average, 29 fps extreme spread, 9 fps std deviation. Group was 2.0"/9 rds/50 yds.... I didn't include the first round in the group measurement .
311467, 32.0 4320: 2000 av, 67 es, 18 sd...... and again, the FIRST round was fully four inches to the left of the group which developed in the x- and ten-rings! The remaining 9 rounds grouped 1.6".
311467, 32.0 4320: 2141 av, 63 es, 19 sd. All rounds landed within the so-called "group", which was 3.1"/10/50.
The flagrant straying of the first rounds absolutely mandates that I re-fire these loads with the addition of a dacron tuft. I strongly suspect that there's something going on with the powder positioning in the chambering of the first round, even though I just pull back the charging handle and release it to slam closed by itself. Since the same phenomenon repeated itself with 311291, although to a lesser degree, it may be that the powder is just on the edge of good burning, and the different positioning in the case might make the difference.
311291, the roundnose, illustrated clearly that yesterday's loads were driving too hard for its tastes.
311291, 30.0 4320: 1866 av, 95 es, 28 sd, 2.2"/10/50. The group was only 1/2" high, but spread pretty wide across the ten-ring.
same, 32.0 4320: 2055 av, 89 es, 27 sd, 3"/10/50.....just a loosely scattered group with nothing unusual about it.
same, 34.0 4320:2161 av, 124 es, 37 es...and a HORRIBLE 'group' (HA!), six- inches- plus in sprawl.
311672 did pretty well to begin with.
311672, 30. 0 4320: 1868 av, 79 es, 30 sd, 1.3"/10/50. Nice group, compared to some others!
same, 32.0 4320: 1976 av, 80 es, no sd reading, 1.6"/9/50... the tenth round was a flyer two inches out at 10:00, no explanation. It was called "good".
same, 34.0 4320: 2116 av, 116 es (high!), no sd reading, 2.5"/10/50....just a general loosening of the group as it neared the load levels from yesterday.
All rounds fired today functioned the rifle perfectly.
The Nevada zephyrs were out in force! It was so bad that I eventually found a BRICK (no kidding) which I used to dampen the flailing-around of my chronograph boom. I did this by duct-taping from the brick on the ground up to the outer end of the boom with considerable tension on the tape. I also had to run duct-tape from the boom just outside the rear doors of the van to the upwind side of the vehicle, to keep the boom from slewing violently down-wind in the gusts (I did this first, and added the brick rig later). The normal retaining notches were not up to the job in the gale.
I estimate the gusts at around 40 mph, and today was the first time I've felt the van actually moving very much in wind. It has a one-ton suspension, so it's pretty stiff. In the lulls which came occasionally, I'd sometimes fire three or four rounds in quick succession to take advantage of the condition. All the wind whistling through Der 'wagen kept barrel heat well under control. At only fifty yards, and with the wind mostly fish-tailing or quartering from behind, I don't believe it affected my results very much.
The learning process goes on....