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Old August 1, 2000, 08:16 PM   #1
Markk9
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I was doing some research for working up some load for my 243Win using 100gr Remmington's I found the data from the Hornady books in my library to be interesting.

1967 IMR4350 43.3 3100 22in barrel
1973 IMR4350 43.3 3100 22in barrel
1980 IMR4350 41.4 2900 22in barrel
1991 IMR4350 41.4 2900 24in barrel

I wonder what happened between the 73 and 80 books?
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Old August 1, 2000, 11:39 PM   #2
Archie
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It may be as simple as changing rifles. Gunpowder (yes, the same brand and type) changes between lots. Sometimes a little, sometimes more. Bullet makers change the material and inner design of their bullets.

That's why all the books say "This load may be over maximum in your weapon. Work up to maximum." Could be your firearm's "max" is greater than theirs, but it would real dumb to assume that.

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Old August 2, 2000, 12:06 AM   #3
alan
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Might be that in 1967, the "legal dept" had less to say regarding the technical content of a book than they do nowadays.
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Old August 2, 2000, 12:09 AM   #4
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Another factor is that pressure testing equipment and methods is constantly improving. What may have produced a reading of say 50,000 CUP (copper units of pressure) with the system used in 1973 may have actually been producing a higher pressure reading with the system used in 1980 all other factors being equal. Therefore they lowered the charge to correct the error.

Even better equipment is available today and you will seldom see the older CUP method used.
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Old August 2, 2000, 08:42 AM   #5
Banzai
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While all of the above posts are true, I suspect that the single largest reason is that the current trend twords litigation has reduced most all charges in most every load manual.

Tom


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Old August 2, 2000, 10:50 AM   #6
Paul B.
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One of the things I find interesting, is in reading Elmer Keith's book, BIG GAME RIFLES, he uses a load of IMR-3031 for the .35 Whelan, that is 5 grains higher than anything I can find in any loading manual today, and not on any of my older ones either. Funny. His rifles didn't blow up. Some powders though, seem to be faster burning today than in past years. For example, a load of IMR-4895 that I've used in the 30-06 with 150 gr. bullets now has to be reduced by 2.0 grains. My pet .357 Mag. load with Alliant's #2400 has to be reduced by 1.0 gr. and by 2.0 gr. in the .44 Mag. I can no longer use Elmer's pet load for the .44 Mag.
I agree that for the most part, liability lawyers strike again, but some of it may also be in the powders, as well.
Has anyone else noticed this?
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Old August 2, 2000, 01:37 PM   #7
Chris McDermott
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Alliant buying Hercules has definately changed some of the powders such as 2400.
I also suspect that the loading book authors now declare maximum when 1 shot of a 10 shot string reaches the pre-determined pressure limit, instead of the 10 shot average reaching the pressure limit. I don't know how else to explain the large differences in the listed max average pressure between different powders for the same bullet/cartridge in the loading manuals.
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Old August 2, 2000, 02:03 PM   #8
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Better science. Many older manuals had pressure readings taken from the CUP method, which *can* be way off if little things are even a tiny bit off, like the hardness of the copper cup or a little misalignment in mounting it in the fixture.

Litigation?? Remember, the guy's *don't* get sued until someone blows up a gun. Sure, the first line of defense is that the guy's scale was off and he over-charged the round, BUT....what if it were you?

We learn more, and quit publishing stupid loads once we find out they're stupid.

IIRC, one powder maker found out that their test-bed .357 Magnum was a single specimen that generated safe pressures (in the days of technically-calibrated "pressure sign" readings) using loads that were close to PROOF level in min-chamber production guns. They backed off their Max charge listings immediately!
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Old August 4, 2000, 08:34 AM   #9
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Speer 11 loads are to hot, starting loads are actually starting loads and not to exceed max loads are actully max loads.

They sure fixed that inconsistancy with Speer 12
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Old August 4, 2000, 12:06 PM   #10
Paul B.
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Something else to take into account. The first loads in .357 mag. (1935) went in the 1525 FPS range with an 8.75 inch barrel. (Later shortened to 8 3/8 to comform to NRA target match regulations.) That was with a 158 Gr. bullet. What is it now? 1250 to 1300 FPW with 158 gr. bullet? The .44 magnum, 1550 FPS in 1956 with 240 gr. bullet. What is it now? around 1250 to 1300 FPS. The .357 used to be a pretty fair deer round, but with the advent of the S&W model 19 and 66, the original loads shook them up pretty quickly with endshake and other problems. (They kicked like hell too, take it from me.) The S&W 29 and 629 are based on a design that came out in 1905, that really did not hold up taht well. (My 629 lierallt destrroys it's hammer/trigger relationship in 200 to 250 rounds of the current ammo.) So the factories downloaded both rounds. .357's loaded to original specs in S&W 27's and 28's are potent rounds more than suitable for deer, and hogs as well.
BTW. The comment about Alliant seemingly making a change in #2400 is well founded, based on my experience with that powder in .357 and .44 Magnums. I think that since DuPont sold out to IMR, the same thing may have happened there as well, although this is based on one lot of powder in one cartridge.
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Old August 4, 2000, 12:45 PM   #11
Alan B
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All things being equal

Well in reloading, I cant name one damn thing that is equal. You can cut down on the variables but never elininate all of them.

Ever weight the bullets right out of the box (+- as much as a grain in some cases)
Powder ( different lots, was it measured by weight or volume)
Brass some cases are thicker other are lighter (Even in the same lot)
Barrel of the rifle (Hotter, colder more worn or brand new from the test)
The test equipment (new or old , digital or analog)

When I start a new load I usually try to cross reference from as many sources as possible to find my "safe" starting load and work up from there.
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Old August 4, 2000, 06:16 PM   #12
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How bullet companies make a load book:
Low pressure, short OAL, and low velocity.

How powder companies make a load book:
Low pressure, short OAL, imaginary high velocities.

How to read load books: Bullet company books, throw them out. Powder company books, change the OAL and increase powder proprotional to change in powder space, also increase powder percentage proportional to another 1/2 of possible pressure increase percentage.
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Old August 4, 2000, 09:41 PM   #13
dongun
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Mal referred to the CUP as a unit for measuring chamber pressure. What does this unit of pressure actually measure? How does it compare to PSI (what would 50,000 CUP be in PSI)?
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Old August 5, 2000, 11:34 AM   #14
Paul B.
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Dongun. Some of the stuff I've seen in the gunrags show a cartridge giving say 50,000 C.U.P. delivering about 60,000 to 61,000 PSI using a Piezo-electric strain gauge. Rick Jamison of SHOOTING TIMES Magazine has been using one for about 3 years now. I based my statement from some of his writings.
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Old August 5, 2000, 12:39 PM   #15
Mal H
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dongun - the CUP system measures chamber pressure, just as you would suspect. The values are derived by crushing a copper "crusher" rod (or lead in some cases)between a piston mounted in a barrels chamber and an external anvil. The more it is crushed, the higher the CUP (or LUP).

CUP values really don't translate to PSI values with a single multiplication factor. As Paul said, one caliber that gets 50K CUP may get 60K PSI (e.g., 280 Rem.). But some other cartridges actually have equal or lower PSI compared to the CUP. The majority of measured PSI values are higher than the CUP values. But again, not in any particular ratio.

Of all the commonly available reloading manuals, Lyman's has the best explanation of CUP and the method used.
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