Precise Propellant Measuring

[Zombie Steve]

Anybody read the John Haviland article in American Rifleman magazine? There was a bit of an eye chart at the end, but I found the differences in velocity, extreme spread and group size pretty interesting when using a powder measure vs. weighing charges.

To sum it up, he tested 5 5-shot groups each: .223 with TAC, .22-250 with Varget, .30-06 with IMR 4350, .357 mag with Unique and .44 mag with (gulp!) Titegroup.

Weighed charges always came out faster (ranged from 1 fps up to 47 fps). With extreme spread weighed charges were much tighter with flake and extruded powders, but with ball (tac and tg) they had better numbers. In terms of accuracy, it was all over the board. Tac did better with weighed charges (by 1/2 moa), Varget did better with measured (by more than 1/2 moa), 4350 did better with measured (close), .357 did better with weighed (by almost 1/2" at 25 yards) and .44 mag did better with measured charges (1/4" @ 25 yards).

I know there are a ton of variables that weren't taken into account, but I'm trying to make sense of it all. Again, I just find it interesting. I would have thought the ball powders would do better with measured charges and flake / extruded would clearly do better with weighing.

John ends the article saying "From this test, it's clear that metered charges are capable of near-identical performance compared to weighed charges..."

Your thoughts?

[Tim K]

Pure speculation here, but basing on volume doesn't make much sense to me. The combustion reaction is a chemical reaction (rapid oxidation), and the amount of energy released is directly proportional to the mass of reactant (powder). Measuring volume introduces the variable of charge density, and that seems like a step backwards.

Maybe there are other considerations like combustion efficiency due to variations in charge compression or something that make controlling the volume more important than controlling the mass. That's far out of my expertise, so I'm back to speculation.

Knowing what I know, which is nothing, I'll stick with controlling the mass of the charge and let its volume vary as it will.

[Zombie Steve]

I guess most surprising to me was the .30-06 with IMR 4350 (big stick powder) was almost a total wash with regard to velocity and accuracy at 100 yards. Extreme spread was 38 fps better for weighed, so it would have a bigger impact on accuracy at distance...

And who the hell uses Titegroup for .44 mag?

[spqrzilla]

I think its more of a matter that the accuracy of a batch of reloaded rounds is more related to the consistency of the physical dimensions, concentricity, OAL, and seating depth than to variations in powder charge.

Not that you can't make an inaccurate batch with variations in powder charge - you can - just that other factors are more dominant. Others have done similar experiments. There was an article on .308 Win reloading with variations on different elements in Handloader some years back that showed similar results.

[Hoser]

The author should have shot some groups at 500 yards. Then his results would have meant something. At 100 yards it does not mean a lot.

[Jamnanc]

Good info. So conclusion is...unless I get into bench rest/ long range, use my progressive.

[sellersm]

Seems like a few too many variables to me. I'm not sure the correlation actually exists, of course I've not read the article yet, but as long as a certain "amount" of powder got into the case, who cares how the "amount" of powder was 'calculated'. Or am I missing something?

Seems like he's trying to correlate items that would appear unrelated: "people with blue eyes prefer oranges but those who are left-handed like to drive Subarus"...

Statistically it seems his sample is a bit low, and as Hoser mentioned, the distance was very limited, even though the chrono seemed his metric of choice.

Just my uninformed two cents....

[Tim K]

Seems like a few too many variables to me. I'm not sure the correlation actually exists, of course I've not read the article yet, but as long as a certain "amount" of powder got into the case, who cares how the "amount" of powder was 'calculated'. Or am I missing something?


You're missing something, mainly the concept of mass. Let's say I'm going to sell you a gallon of gold. Assume the gold in all three of the following examples are the same purity. Does it matter to you if I sell you a gallon of old gold earrings, old gold earrings that have been smashed down tightly, or gold powder? Is a gallon of gold the same amount of gold in all three cases?

This is why gold is sold by the ounce not the gallon.

[Jamnanc]

But any specific lot of powder "should" weigh the same amount per any volume which is why one weighs a charge after setting up and checks to make sure the volume/weight is consistent. Which, so far, always has been for me.

[Hoser]

Most all short range benchrest shooters just throw charges. They use very expensive and accurate measures, but you will rarely find a scale at a point blank (100-200 yards) Benchrest match. For their application just throwing charges works. They dont even speak of grains of powder. They speak in clicks.

The 600 and 1,000 yard benchresters get nuts about everything. Kinda cool actually. When you can put 5 shots into a group of less than 2 inches, at 600 yards, you have done something.

But when you get into large kernel powders and lots of it, best to break out the scale.

[sellersm]

But when you get into large kernel powders and lots of it, best to break out the scale.

Ya gotta measure those Corn Flakes!! [Coffee]

[Jamnanc]

Agreed. I haven't loaded for anything heavy in a while, most is production and cheap so I can afford to shoot/stockpile. When I was loading for hunting, I weighed every charge and trickled with an empty case.

[Zombie Steve]

The one that surprised me the most was the .30-06. Almost a total wash with IMR 4350 ( a big stick extruded powder). The extreme spread numbers would favor weighed charges at distance (like Hoser says). Just kinda shocking that it didn't matter for accuracy at 100.