Some of you may have seen this query on 24hourcampfire -- thought I'd try here and see what other feedback I could get.

I had a problem with a load that was extremely accurate when first developed and I don't think I've shot it enough to burn out the barrel. When first developed it would go into .4" or less for 3 shots at 100 yds, now it's more like 1.4".

.375 H&H
235-gr. Speer SP
62.0 gr. IMR 3031
CCI 250 primer
Rem. brass

When first developed I loaded these in new brass. As mentioned, they shot great. The brass was not sorted in any way since I didn't yet own a concentricity gauge (ignorance is bliss) -- just sized to straighten out the neck, trimmed for consistent length, deburred and chamfered.

The latest batch was in once-fired brass, sized just enough to chamber easily, and checked for neck runout and consistent neck thickness. This rifle seems to have a pretty tight chamber by belted magnum standards; I use the Redding Competition shellholders and a once-fired case needs to be sized with the +.002" shellholder (that is, almost full-length sized) to chamber easily. Most of my other rifles take a couple sizings with the +.010" shellholder, then need a "shoulder push" with the +.004" or +.006".

I'm pretty sure the only difference was the case -- all other components were from the same lots.

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Based on feedback on the Campfire I tried the "Optimal Charge Weight" method that Dan Newberry ("Wizard") has promoted here:

The test gun was a .375 H&H Interarms Whitworth, equipped with a Leupold 1.5-5 variable set on 5x throughout.

All loads consisted of the 225-gr. Hornady Spire Point (different bullet but I was out of the Speers and thought an untried bullet would be more "impartial"), loaded in once-fired, partially sized Remington cases, sorted for consistent neck thickness and primed with Federal 215M primers (which also eliminated the misfires I've been having with CCI 250s). Bullets were seated to the cannelure to allow easy loading, which gave a loaded length of 3.935" to the ogive as measured on a Stoney Point comparator.

Since I had previous good results with the Speer 235 and 62.0 gr. of IMR 3031, I decided to start with that charge as the "center" of my test series with the new bullet, then work up and down in 1% increments. 5 rounds each were loaded at each charge to allow spares for cross-firing as Dan recommends on his site, and to allow for any misfires or chrono problems.

Groups were fired "round robin" style; barrel was allowed to cool until it was not warm to the touch. Results of firing were as follows. Note that all group center shifts are described in relation only to the previous target:

Target 1 (T1) - 60.8 gr.: avg. 2536 fps, 3.01" group
T2 - 61.4: 2549 fps, 1.28", group center shifts down 1.5", right 1.25"
T3 - 62.0: 2603 fps, 2.64", shift up 0.75", left 0.5"
T4 - 62.6: 2585 fps, 2.15", shift up 0.5", right 0.25"
T5 - 63.2: 2594 fps, 1.01", shift 0.5" left, no elevation change.

Since I wanted to follow Dan's method as fully as possible, I took T4 as the optimum since it had the lowest then fired one each of the remaining 62.0 and 63.2 rounds at T4. Both landed comfortably within the admittedly large group. The shot with the 63.2 gr. charge landed in a spot where, had it been fired at T5, it would only have been 0.5" from the center of that group and would not have increased the size of that group.

If I were going to fully explore the potential of this method right now, I'd shoot another series, probably starting with 63.2 gr. as the center target. However, due to a long-scheduled construction project at my range, as well as my own wedding and honeymoon and a friend's wedding shortly thereafter, on top of a busy work schedule, I doubt I'll have enough time or bullets to do that before hunting season.

So I think for purposes of running through this box of bullets, I'll take 62.6 as the optimum. It doesn't seem to be too far off, anyway. My next step will be to load a few rounds with new brass, and a few with once-fired, and shoot a comparison series.

I should add a note on my chronograph readings. They probably aren't very useful. Due to the width of my target array, shots on either end were passing over the skyscreens at an angle, so I think I got some low readings, especially on T1 and T5.

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Next I tried that same load -- with some loaded in new brass, some in twice-fired:

The loads I was testing were exactly the same except the brass: 225-gr. Hornady SP, Fed. 215M primer, 62.6 gr. IMR 3031. Half the brass was new and had been run through a Redding FL sizing die to true up the necks. The other half had been fired twice in the same rifle, and resized enough to chamber easily.

I fired two fouling shots then three-shot groups for each load at 100 yds. I alternated to minimize the advantage for either set, and allowed the barrel to cool to the touch between groups -- about 20 min. at the range temperature of 76 deg. F. I also didn't pull any shots, in fact generally shot pretty well today. I got the following results:

NEW CASES:
1. Avg. 2562 fps, extreme spread (ES) 17.83 fps, 0.51"
3. Avg. 2583 fps, ES 44.94 fps, 1.72"
5. Avg. 2549 fps, ES 30.03 fps, 1.93"
AVERAGE GROUP SIZE=1.39"

TWICE-FIRED CASES
2. Avg. 2595 fps, ES 69.19 fps, 1.36"
4. Avg. 2592 fps, ES 96.00 fps, 2.68"
6. Avg. 2588 fps, ES 25.33 fps, 1.99"
AVERAGE GROUP SIZE=2.01"

So it appears the new cases give more consistent velocity, better accuracy and (not shown in the numbers but very clear on the targets) much more consistent point of impact.

Note also that this is a load that was originally worked up, both in my first attempt and in the "OCW" trial, in once-fired brass. So normally you'd think that throwing it into new brass introduces a new variable.

I'd love some comments from anyone who's read this far.

John, i feel there are a few things you should change for your test. Shoot 5 shot groups (yes i know its a 375). For testing put on a scope of higher power 18 to 24x, less sighting errors. When loading for my litte 243win. with std dies, some times the new brass will shoot better till the neck wall gets thinner, then accuracy drops off. Neck turning and bushing dies are a different story. Have fun, i think you just like to shoot like the rest of us. 243winxb

Appreciate the suggestions but don't think they're really the problem.

I don't have a single scope that goes over 9x, and regularly shoot sub-MOA groups with this and other rifles. As long as the target is big enough to be visible around the crosshair intersection, more magnification does nothing IMO except magnify my wobbles.

I know there might be more statistical validity in 5-shot groups. But in Virginia summer temperatures, 5-shot groups are a good way to burn the barrel -- that, or take all day to shoot a couple groups. John Barsness once reported from testing with a bunch of rifles that generally a rifle's 5-shot group would be 1.5 times bigger than its 3-shot group. (He still shoots 5s from varmint rifles because they will be shot with hot barrels and he needs to know what they'll do.)

Back to the subject -- I realized later that I'd never measured loaded-bullet runout. So I loaded up some good, straight cases with 4 each of the following: 225 Hornady, 235 Speer, and 270 Hornady.

The 225s averaged about .006" total runout, while the 235s and 270s were more like .004". In the batch I loaded to use up the rest of the 225s, I got a fair number with runout in the .009-.012" range. So I suspect that was the source of some of the results in my extended test with those bullets.

John

John,
All looks well for a 375 H&H, you need a full time job, your worrying to much about things that are of little consequence!!

this is Bench rester stuff!! applicable to a 6 PPC etc,.