I am real curious about some of the Reloading Manual's and there Data.Especially in the 45-70.Sorry I have other guns too,But this one stymies me.

From Joe at Real Guns.

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This is from Joe at Real guns..


The Model 1895G Part II - Handloads for the .45-70

But first, the un45-70, the .450 Marlin

I was preparing a list of loads I would work up for the .45-70, and I wanted to get a better feel for the pressure dynamics of both the .45-70 and .450 Marlin, get a better understanding of the relationship between the two cartridges and see how far the new cartridge exceeded the full up loads for the .45-70. I ran across the July 2000 "Shooting Times" .450 Marlin article, so I looked through the data, pulled out all of my manuals, and poked around in the various smokeless powder companies' web sites.

Source Cartridge Bullet Powder Charge MV Barrel
Shooting Times .450 Hornady 350 gr AA2015 58.0 2041 18.5
Hornady .45-70 Hornady 350 gr AA2015 59.4 2000 22.0

Same bullet, less powder, 2.5" shorter barrel, yet, the Shooting Times .450 Marlin load out performed the hottest 5th Edition Hornady Ruger No. 1 .45-70 load. The article rated the .450 load at 40,200 psi, while the Hornady listing for the larger capacity cartridge has the .45-70 load at 50,000 cup. When you run both of these loads through reliable interior ballistics software, both come in below 40,000 psi, within 200 psi of one another. This odd load result could have been an anomaly, but it wasn't. The Shooting Times data also didn't track with the Speer #13 reloading manual.

Source Cartridge Bullet Powder Charge MV Barrel
Shooting Times .450 Speer 400 gr N-133 52.0 1994 18.5
Speer .45-70 Speer 400 gr N-133 59.4 1995 22.0

There were bullets included in the review that won't cycle through an 1895. Even Speer specifically excludes their own 350 grain bullet as excessively long for use in this gun. While the ejection port and bolt travel are long enough to clear almost a 2.900" combination, the feed and ejection mechanisms are not. You can expect feed and eject reliability problems to begin appearing above 2.600" COL. Most reloading manuals peg bullet seating depth to result in a 2.550" COL.

My point is not to critique "Shooting Times", they are obviously a first class publication with a first class staff, and clearly a greater mastery of the English language than I could ever muster. My point is, the industry sometimes becomes a little overzealous in putting their seal of approval on new products, while the new products may not actually have much to offer. As a result, data tables and conclusions be set aside as not being credible, rather than serving as basis for understanding
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Pretty crazy isn't it?It just goes to show sometimes independent test are much better than "Some" Reloading Manuals in actual Pressures and Velocities.

Were on our own with Mr. Common Sense..............................Jayco

Inherent variability.

Niether the CUP system nor the piezoelectric PSI system is very repeatable. If you load exactly the same cartridge, and use the same equipment, same technician, and same lab, either system will routinely produce 10-shot averages that are off the true value by plus or minus 1,000 PSI. Throw in different equipment, in different labs, with different technicians, and it will get worse.



So one lab's upper limit can be another lab's starting load, just from random variation in the pressure measurement system.



The piezoelectric system would be a lot better if SAAMI would control barrel temperature as rigorously as they control ammunition temperature. That uncontrolled variable seriously degrades the repeatability of the piezo system.



See Varmint Hunter July 2003 p92.



Not quite as short as Jackfish's comment, but to the same point: Inherent variability.

Noise = Random Variation

We are probably in violent agreement on the concept.

If you Pareto the variables that influence accuracy, there are several that are large, identifiable, and controllable. So you use the same amount of the same powder, and you eliminate barrel rubs, etc. Finally you get down to variables as small as the heat that is transferred to the cartridge as you handle it, and the way that the powder happens to lie in the casing. Those small variables, too small and too numerous to control, you lump together and treat statistically. A process dominated by many small sources of variation will have a strong tendency to be random and normally distributed.

The random error that I was referring to is the random error in the measurement system, which is ample. If you fire two identical cartridges, under identical circumstances, they may produce equal pressures, but your measurement, using either PSI or CUP, will likely not be the same. Both those measurement systems are infested with lots of random noise... many sources of variation, too small and too numerous to identify and control, with one big exception: Barrel temperature is a very strong variable in pressure, and the SAAMI procedures do not control it, so it shows up as part of the random noise.

Whether we agree or not, nice to meet you, and keep posting.

Denton,
Your going to do all this with a 45-70? then it will shoot a 5 inch group as opposed to a 6 inch group!!

Just kidding, but you really can't make a silk purse out of a sows ear...the 45-70 is a 100 yard grapefruit gun and if you have one that will consistantly shoot 3 inches you have a very exceptional rifle and sure a few will do better.