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A friend's brother-in-law, brand-new to shooting and loading, is properly very cautious with his loading. He's also very sensitive to recoil, my friend says.

NOT a good combination for getting a Ruger Number One .375 H&H Magnum! for increasing his abilities at the bench and in the field. He plans to use it for black bear soon and for grizzly or brownie eventually.

Fortunately, one of my current QuickLOAD projects � strictly academic before this application came-up � is to study ways to reduce loads for plinking and practice without complicating the interior ballistics. I was using the .35 Whelen (a purely arbitrary choice) for my test pig, but now I'm going to use the .375 H&H Magnum instead.

For starters, I ran a couple of quick simulations on QuickLOAD � with the 220-grain Hornady at 25,000 lb/sq in. and the 300-grain Sierra at 60,000 lb/sq in.

Here's what I just PMed my friend �


I'll have more on this study later � after I've run several simulations from 15,000 to 60,000 lb/sq in. Pmax, in 5,000-lb/sq in. increments.

This is really going to be interesting! (I just hope that TLEE doesn't have a cat named "Curiosity!")

More than just curiosity from me ( no puddy tat though), but so much that I don't know on interior ballastics that I have to start from an elementary position.



That's a huge difference in PSI. My first curiosity is what is the SAAMI maximim for the 375 H&H? I'd have no interest in exceeding (or even nearing) the maximum. So, with fingers, eyeballs, and other body parts safe from extinction, the next question would be what is the lowest PSI that would reliably work? As a follow-up, what would be the failures, should a load be under that PSI level?

SAAMI's maximum is a safety limit � nothing more, nothing less, nothing magical, nothing mandatory. It's solely a matter of which guns that particular ammo is loaded for. Strong new breeches in good condition are far less risky than older, weaker lock-ups, so the SAAMI maximum for cartridges that'll be fired only in those safer breeches is of course higher.

For the .375 H&H Magnum, it's probably (as it is for cartridges like the .270 and .30-06) around 60,000 lb/sq in. (maybe a tad higher) � much higher than the SAAMI Pmax of cartridges like the .30-30 and the .38-55. The .375 H&H Magnum is fodder for bolt-action rifles � the .30-30 and the .38-55 are going to be fired in lever-actions, many of which are very old, so their SAAMI maximums are appreciably lower (probably not far from 35,000 lb/sq in.). I could look 'em up if I knew where my SAAMI books are � and if knowing 'em would be necessary for my purposes.

SAAMI's Pmax is a maximum. IOW, by definition, not to be exceeded. Field experiments with individual guns would be necessary to identify the practical minimums for good accuracy, consistency, etc � de facto field conditions that software can not predict.

The purpose of my very preliminary look at 25,000 and 60,000 lb/sq in. was to see how low I could go, and how the results of that lower Pmax would compare with the results of the maximum Pmax � to establish practical brackets for my detailed study.

The lower the percentage of the case fill, the more erratic the load is likely to be � with the powder bunched down against the web in some rounds, strung-out along the length of the case, or bunched all the way forward against the base of the bullet. Therefore, I'm interested only in loads that fill 90�100% of the case. Practical reduced loads almost certainly call for a different powder, not merely less than the full charge of the top-velocity powder.

Found a list of SAAMI maximums here � http://www.handloads.com/misc/saami.htm

Here are a few from that list �
� .270 Winchester � 65,000 lb/sq in.
� .30-30 WCF � 42,000 lb/sq in.
� 7-30 Waters � 45,000 lb/sq in.
� .30-06 Springfield � 50,000 CUP
� .338 Winchester Magnum � 64,000 lb/sq in.
� .375 H&H Magnum � 62,000 lb/sq in
and notice this �
� .45 Colt � 14,000 lb/sq in.

15-odd years ago I also experimented with reduced loads for a #1 in .375, and the 220 Hornady was startlingly accurate. I was using faster powders, though - 3031 IIRC, and had to use a filler or else ignition was not consistent. The filler worked fine for me in that case, but I gather they are somewhat controversial.

Dr. Howell, I recall reading John Barsness commenting about some powders not performing well unless pressures were in normal working ranges. He mentioned Ramshot TAC in that case.

I'm inferring from your posts that a good path to reduced loads is powders that are normally "too slow" for the cartridge and bullet in question, but fill the case. That's an interesting idea for a big boomer I was considering, if indeed it is feasible, and I don't use a powder that wants to be in a different pressure range.

Dr. Howell:

A year or two back, maybe even further back, you mentioned that you knew, or suspected what caused higher than normal pressures when loading reduced amounts of slow powders, such as 4831 in cartidges like the .270.

I don't remember if you ever gave an explanation or not, but I would like to know if you really can get abnormal pressures with reduced loads, or if the reason for these blown up rifles is most likely caused from using the wrong powder.

By this, I mean, thinking you reached for the can of 4831 and actually picked up the can of Bullseye.

I know they are measured by different methods but is there a simple mathematical formula or rule of thumb calculation that could roughly convert CUP to PSI?

Denton posted on awhile back. Maybe he will read this.

IIRC, PSI is about 20 to 25% more than CUP. For example, the .30-06 listed above at 50,000 CUP would be about 62,000 PSI, but it varies between cartridges loaded to different pressure levels.

Actually, CUP is PSI. CUP is the pressure in PSI as measured by the Copper Crusher Guage and PSI is the pressure in PSI as measured by the Pizzo (Sp?) gauge.

No.

I say this after reading every word I can find that Ken Oehler has written on the subject. A guy who has seen more proof houses, and ballistics labs than 'bout anyone.

OK.



Reinforced, that's good.



That's where I falter.

Knowing which powder, and charge weight will produce a given PSI, in a chosen cartridge (given a bullet weight/type).

I should've said "drastically" reduced loads, I reckon.

There's a solid kernel of truth in the misapplied old hick "reasoning" that "If they don't mean for that there ca'tridge to be full o' powder, they wouldn'a made it that big." The crucial question is "which powder?" The .300 Savage and the .308 Winchester are almost identical in all dimensions, yet SAAMI has assigned different pressure maximums to them, and I'm sure that they're both full of different powders.

Loading just a bit slightly lower is quite different, in interior ballistics, from loading a lot lower. The less powder there is in the case, the more sensitive the powder is to its position in the case when the primer flash lights it off.

Somewhere along the way (I don't know where, exactly � that probably depends on which powder snd which cartridge), the ignition and the combustion of a greatly reduced powder become so drastically erratic that pressures can vary from dangerously high to disappointingly low. If that drastic performance is only inconsistent, that's bad enough, IMHO. But the more erratic it gets, the more danger there is that a wild up-swing in pressure will convert the heart of the gun into flying shards.

Loading for a drastically lower pressure, while keeping the percentage of case fill near 100%, calls for powder with a different quickness. IOW, a different powder.

Loads at any pressure are more likely to be consistent when the powder fills the net space in the case full or nearly full.

There's just no way to fill the case full or nearly full with the powder that produces high pressures and expect it to generate significantly lower pressures. Drastically reducing the case fill raises the probability of inconsistency � sometimes from probable to unavoidable � even to risky and dangerous.

Be not discouraged!

None of this surrenders to intuition or imaginative theorizing, so no one should assume that it should be obvious to everyone who rolls it around on his brain.

If you still can't "get it," let me know � and I'll try to explain it better.

I've got a pretty firm grip (relative term,>grin< ), that different powders, with different burn rates, and different densities, will occupy varying amounts of volume - and produce vastly divergent pressures in the process.

I'll take the .300 Savage you mentioned ('cause I like 'em). The effective case capacity (full, minus displaced water) comes in at 'bout 48 grains of water. So, with that amount of volume, how do I select a powder that fills the case to 95%, and produces 35,000 PSI?

Then, how do I select a powder, to fill the case to 95%, and produce 30,000 PSI; 25,000 PSI, and so-on?

As an aside, I had a devil-of-a-time finding this thread. I thought it was in the Hunter's Campfire.

Proof positive, that I'm not 95% myself! >grin<

That's what I'm going to be doing for the .375 H&H, using QuickLOAD.

I'm going to "turn in," in a few minutes, for the rest of the night. PM me which bullet to use in a simulation for the .300 Savage, and I'll run it through QuickLOAD later.

For now, I've just run a QL simulation for the .300 Savage with the 150-grain Speer seated for an over-all length of 2.60 in., fired from a 24-in. barrel. QL estimates that �
� 43.7 grains of Vihtavuori 550 would fill 96.2% of the case and generate about 2,500 ft/sec at 35,000 lb/sq in.
� 42.5 grains of Accurate 4350 would fill 100% of the case and generate about 2,350 ft/sec at 30,000 lb/sq in.
� 40.2 grains of Accurate 4350 would fill 94.8% of the case and generate about 2,200 ft/sec at 25,000 lb/sq in.

Remember, whatever QuickLOAD estimates is just that � an estimate � not a prescription! You'll have to be as careful as usual with how you begin and develop your work-up.

One good thing about all this, of course � at those moderate pressures, you're not going to get signs of excessive pressures, so you'll be interested in developing your most accurate loads.

I'd suggest using one bullet for your lighter loads and a different bullet for your heavier loads � to make it easy to tell which is which without depending on labels.

(The similarly titled thread in the "Hunter's Campfire" forum was just a link to this one.)