Powder lots?

Ray B

I used up one container of Green Dot and started on another. As part of the start-up I run the new powder through the presses, dropping 10 charges and /10 to get average weight with each bushing. This lot of Green Dot results in weights of nearly one grain in the small bushing and more than two grains in the larger bushings, lighter than the previous lot. Is this a normal variance- should the loads (shotshells) continue to be loaded by weight?

perry shooter

I dont load shot gun shells But have loaded hundreds of thousands of 45ACP.Different lot numbers do weigh different. One reason is how they are stored and what they are stored in . Because When I started loading Powder cans were CANS made of steel. Later they when to cardboard and still later went to plastic. Plastic and metal are for the most part water proof but cardboard will allow the powder to absorb moisture . and the same volume will weigh more .on top of that different lot numbers can give different pressure . I load match grade ammo and I have to adjust load for each lot number . Don't want to sound like a SNOB BUT I don't think you will see any difference in a SHOT GUN LOAD

Mobuck

I loaded shotgun shells for years before I had a powder scale. Bought powder 1#(Red Dot or Green Dot) at a time cause that was my budget. No idea how much variation was involved. Never had a problem. Of course that was loading moderate trap loads, not max load magnums.

navc130

The theory of powder lots, as I understand it, is that a given weight of a powder charge will give the same pressure and velocity from different lots of powder. So, yes, use the same weight charge.
A call to the manufacturer or a good reloading book covering the subject would be beneficial.

Tailgunner1954

quote:Originally posted by navc130
The theory of powder lots, as I understand it, is that a given weight of a powder charge will give the same pressure and velocity from different lots of powder. So, yes, use the same weight charge.
A call to the manufacturer or a good reloading book covering the subject would be beneficial.


That isn't true either.
To be safe, always start over at the minimum charge and work back up when changing powder lots.

nononsense

Ray B,

The rule for switching powder lots is to:

Start low and work your way up slowly to avoid over-pressure excursions from lot-to-lot variations.

These variation from lot-to-lot can be significant. This was most noticeable in lots of Reloder-25 (slow) which had the performance of Re-19 (faster). The results were near catastrophic when fired without load development testing.

Best.

Rocky Raab

It's the amount of actual powder that matters. Weight variance can occur with the amount of residual solvents and/or moisture in the powder. That's why shotshell reloaders use fixed volume inserts and not powder weight.

An analogy to help understand this is a sponge. A given sponge will have the same amount of "spongeonium" in it regardless of if it is wet or dry - but the weight will change dramatically. If you cut a wet sponge up until it weighed the same as a dry one, you'd have a whole lot less actual spongeonium in your scale pan.

Gunpowder doesn't change weight nearly that much, but there is some amount of change depending on the solvent/water content. New powder normally weighs a bit more per volume because its liquids haven't evaporated yet - and that's why you might see a bit less velocity from a new can of powder if you adjust your measure to throw the exact same weight as the old can of powder: You've actually used less of the new powder.

bambambam

The guy I buy powder from always reminds customers to not ASSUME that on bottle(or lot) will drop the same as another.

What load are you loading?(shell, primer, wad, powder/powder charge)

If it's a high pressure load, one or two grains could be significant.