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Old May 4, 2019, 02:56 PM   #10
Join Date: March 4, 2005
Location: Ohio
Posts: 16,634
You'll have to ignore Mr. O'Heir on this topic. He doesn't seem to understand that a volume doesn't care what label you put on it, it is still that same volume, and volume may be used to measure gunpowder just the same as a measuring cup calibrated in fluid ounces can be used to measure flour and sugar and is not deterred from that task by being called a "liquid measure".

Many folks have learned to throw from dippers within a couple of tenths of a grain and a few will claim the ability to get 0.1 grains, but I have never been able to hold it that tight for very many throws. It is a matter of practicing to get your technique a uniform as you are able from one throw to the next. However, most cartridges don't require 0.1-grain precision. I've pulled down military ammunition and found a spread of 1.2 grains in charge weight, and that is with a spherical propellant. How anybody can throw spherical charges that inconsistently, I'll never figure out, but apparently the high-speed reloading equipment can. Federal's famous Gold Medal Match load for the .308 Winchester with the 168-grain Sierra MatchKing bullet is something I've pulled down a couple of times and in both instances found it was about ±0.4 grains in charge weight.

If you want to shoot long range benchrest rifle matches, you need 0.1-grain precision and volume precision combined. But at 100 yards my old Remington 600 in .222 Remington drilled consistent cloverleaves using a Lee scoop and IMR 4198 and would do it all day long and, as those were early years for my reloading, I would guess the charge varied at least half a grain.

As for powder, if you want to go from catsneeze loads all the way to full power, you will need at least two powders unless you are willing to waste a lot of powder on the squib loads and clean a lot of unburned powder out of your guns afterward. Slow powders are needed for the highest load levels, but they need high pressures to burn efficiently and reasonably completely. If you don't reach those high pressure levels with them, they can sometimes squib out and leave a bullet stuck in the barrel. A fast powder won't do that, but you also can't use enough of a fast powder to equal the gas volume a slow powder charge produces without making it burn so fast it drives the peak pressure above normal limits. This happens because it doesn't give the bullet time to move forward much before the peak is reached. A slow powder does give the bullet time to move a bit and therefore reaches the pressure peak in a higher volume, lowering the peak value.

So, there you have it. There are actual reasons for all those different powders you see on the shelf.
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