Powder numbers?

1917watercooled

I was in my powder storage yesterday, looking for a suitable powder for a new loading. It struck me that I may have too many kinds of powder but, more than that, all the numbers. They go from AA#2 to 4895. Is there any sense to what the numbers are for, or do the manufacture's just make a number up as they develope the powder? Thanks

FWAddit

Some manufacturers have devised number codes to designate relative speed within a group of powders--say pistol or shotgun powders--but they are not necessarily consistent either with themselves or with each other. And IMR number designations are simply arbitrary.

There are two safe ways to determine what a powder is useful for: check manufacturers' product lists and study loading manuals. Many loading manuals also reprint manufacturers' lists, making it easy to cross-check between powders.

In Appendix D (p. 458) the 48th ed. of Lyman Reloading Handbook consolidates the lists into a single relative burn rate chart, which may be your best bet for reference. Just don't use it to interpolate your own loads in place of actual tested loading data

Rocky Raab

Here's a trivia item for ya:


IMR numbers are NOT arbitrary. They represent the "test batch" number that worked out well enough to be made into a canister powder. You can roughly date their creation by putting them into numerical order. So 3031 was their 3,031st test batch, 4320 was their 4,320th, and so forth.

Creation does not equal commercial introduction, however. They standardized several powders long before they were sold commercially, so creation dates and introduction dates differ.

Ray B

Continuing- since the general trend in powder development is developing slower powders, the larger the IMR number, the slower the burn- but there are enough exceptions that it can't be used as a rule.

geeguy

Rocky, great trivia. Now that's the type of info you remember!

I'll slip that one into a conversation somewhere and WOW everyone.

FWAddit

Hey, thanks for the correction, Rocky. Interesting to know.