Weighing vs metering powder

[tlk]

I have read about how FGMM loads vary quite a bit by weight but are consistent from shot to shot. The comment has been made that they are metering their charges, not weighing them.

Out of curiosity and ignorance on my part, how would one meter a charge?

Thanks.

 

[rscott5028]

Lee includes a dipper with their dies and load data based on the number of scoops. ...just like measuring flour to bake a cake.

There are also powder dispensers available with a handle that you toggle up and down to fill and dump a hopper that's adjustable via a screw.

Such setups are often used with progressive presses when volume shooting is more important than actual precision. By that, I don't mean it can't be precise. Rather, it's more frequently used in that manner. ...and, much more so with shotguns and pistols.

-- richard

 

[Joe King]

Makes me wonder what their definition of "consistent" is

 

[Kevin Thomas]

tlk,

This sounds like a terminology issue, as I'm not aware of any commercial maker that actually weighs their charges priot to dropping them. I don't know whether Federal is plate loading or using an in-line system, but the charges are almost certainly dropped via a measure, or "meter" which is (I suspect) where the confusion here comes from.

Richard has explained this, and I'll go with his explanation completely. I have seen Lake City weigh their ammo, and they still do this as a regular part of their inspection process. The purpose there, however, isn't to ensure the precision of a charge weight, but to guarantee that each round has enough powder inside to postively assure that it can't stick a round in the bore. Very bad form in combat ammo, and makes for very unhappy troops!

 

[tlk]

Thanks for the info guys. Mystery revealed. I have those same tools Richard - I can see where the weight variance would come from.

Based on a 30 cal cartridge I can see how it could be considered consistent inside of an acceptable window.

 

[rscott5028]

I have a police sniper buddy that shoots the 168 FGMM ammo ~.5 MOA at 500yds. Not bad for factory metered ammo.

I've shot Lapua 6br loaded ammo better than that and from what Kevin stated, it's likely a metered charge as well.

-- richard

 

[MT4XFore]

Interesting question. I do both. For my large cases used for big game, I weigh each and every charge using an RCBS chargemaster. For my varmint loads I use an RCBS benchrest powder measure. I set the measure up using the scale on my chargemaster. I will load 10 or 20 rounds, then check the measure on the scale to make sure it is still throwing the correct amount. If it isn't I will adjust it, but it is never far off. I found that if you move the powder baffel down in the measure hopper as far as it will go, the measure will throw extremely consistent loads, depending on type of powder used. I am using Ramshot ball powders for my 22-250AI and my 223AI. Those powders measure like water! Very easy to get consistent loads. I have read where "volume" is actually more important than "weight" when it comes to powder loads. I cannot comment on that as a rule, but my 22-250AI shoots 1/2" groups consistently at 200 yds. using thrown powder charges. If I miss a prairie poodle its because I didn't do my part, not because of my equipment or ammo.

 

[dieselboy427]

The reason people use volumetric charging is an issue of air/fuel ratio. Think engines. The air column being consistent and in proper proportion to the fuel(powder) is more important than the weight of the powder. Remember, just like a bag of potato chips, the particles of powder can and will be smaller in the bottom of the container resulting in a change in air/fuel ratio when loaded by weight.

 

[Lefty7mmstw]

When I'm at or very close to the top load, I weigh the charges. When I'm tossing lighter loads I don't bother unless it's coarse stuff like 5010. I usually weigh with the coarser powders to be sure of what I've got as they can vary up to a couple of grains with large charges.

 

[Bart B]

Metered powder charges can easily produce 1/4 MOA groups through 200 and sometimes 300 yards. And 1/2 MOA at 600 yards. But the powder and primer make a huge difference. So does the rifle's barrel and how the rifle was put together.

Benchresters typically meter charges for use through 300 yards.

 

[boomtube]

"Think engines. The air column being consistent and in proper proportion to the fuel (powder)"

No; think solid rocket fuels burning in space. Unlike internal combustion engines that requre fuel:air (oxygen) mixes, gun powders (and solid fuel rockets) include sufficent oxidizers as part of their composition.

I'm a hunter and gun/ammo tinker-er, not a range rat. My current ammo needs are modest compared to what it was when I shot NRA match rifle competion so even tho I do weigh most of my rifle charges I don't kid myself that highly consistant powder charges in a well developed load can be improved by precisely duplicated charges. I know by experimentation that powder charges have to vary several tenths before it'll show up on targets or deer or varmints ever at some quite distant distances! In fact, I spend a lot of time spinning my wheels with loading techniques that are lost on common factory hunting rifles but I enjoy it so I do it - but I don't do BR type stuff because I think it matters on my targets because I know most of it doesn't!