Progressive presses and powder measures.

Wednesday, April 01, 2009 Filed in: Reloading, Ammunition

A common complaint with progressive presses is the throwing of inconsistent powder charges. Most people immediately blame the equipment, but some times it's actually operator error.

We first need to admit that there are certain incompatibilities with regard to some measures and some powders (Dillon's difficulty with metering flake or extruded powder, for instance, is often discussed on the various reloading forums.) However, even with a powder the measure "likes" unexpected variances often occur during a production run.

The variance usually comes as a surprise to the operator. During setup, the reloader is careful to check the powder charge, and finds that the measure it properly set up and is throwing charges with little variance - say, within .1 grains. During the middle of a run the person happens to check a random case and finds that it is perhaps a half grain off. He stops, carefully throws several charges, perhaps adjusts the measure, then settles down to again crank out the rounds. Another random check, and the process repeats itself.

Perhaps some attention to technique will cure the problem.

Those who reload rifle cases for extreme accuracy will agree that one's technique with the powder measure is critical to consistent, accurate charges. The same is true for the measure on a progressive press!

As it happens, there is a "dwell time" when powder is being dumped from the measure. The powder doesn't fall instantaneously into a case, it flows - out of the measure's cavity, down the drop tube, through the powder die, and into the waiting brass. That journey takes some time, and if the press operator is impatient - or worse, inconsistently impatient - there may be a few flakes of powder left somewhere in the path when he decides to go to the next round in the queue. That translates into a light charge for the current case, and a heavy one for the next.

There is a solution: when you pull the handle down, pause for a second at the bottom of the stroke to give time for all of the powder to make the journey to your case. Most operators I've observed don't do this - as soon as the handle hits bottom, they immediately jerk it back up to get to the next round in the shellplate. That may not give the powder enough time to drop, and can lead to those inconsistent charges.

When I'm using my progressive, I think consciously about that pause at the bottom of the stroke. When the handle hits the stop, I open my hand then close it; the amount of time it takes to do that is sufficient for the powder to drop completely (and has the added benefit of keeping my hand and arm from tiring during long loading sessions!) Yes, it will slow you down slightly; I think it's a small price to pay for more consistent and accurate ammo.

-=[ Grant ]=-
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