One of the problems with ball powders in match loads has been poorer temperature stability than some of the sticks have and less consistent ignition. The new StaBall 6.5 and other stabilized formulations with newer, easier-to-ignite deterrent chemistries are starting to appear, so match load performance may well be improving.
dahermit said:
Wouldn't the G.I. duplication load use Midwest Powders WC844? Isn't that the supplus powder obtained by pulling down G.I. 5.56/55fmj loads?
As I mentioned before, H335 is WC844. The only difference is that H335 is canister grade WC844 rather than the bulk grade surplus. The difference is a canister grade burn rate is more tightly controlled from lot to lot than a bulk grade burn rate is. The control is accomplished by making a bulk lot, measuring the burn rate, then adjusting it by adding some portion of a faster or slower held-back past bulk lot of the same powder type and blending it in (called milling) to increase or decrease the new bulk lot's burn rate, whichever is needed to adjust that lot.
The surplus bulk WC 844, being unmilled, will have more burn rate variation from one lot to the next than the canister grade version of the powder does. The military ammo maker doesn't care about that because he tests loads in a pressure and velocity test barrel and adjusts the final load to meet pressure and velocity and gas port pressure specs simultaneously. If he can't find a load that does all three with that lot of powder, the lot is disqualified for the load being developed, and a different lot is tried. A disqualified lot is either used in something else or is put up for sale as surplus. From there, it either winds up in the hands of the surplus powder dealers, or it is bought by Hodgdon, who sends it out for testing and milling to become canister-grade powder.
The reason canister and bulk grades are separate purchase options is the former's extra testing and milling steps make it more expensive. That expense is necessary for a powder that is to be loaded from a recipe in a databook, as the usual -10% to max load range is not adequate to cover the variation in some lots of bulk powder. In one extreme case I am aware of, a bulk lot of WC846 was 30% faster than the target burn rate (less than half that much variation is more common).
So, to find load data for a new lot of bulk-grade powder requires more care and can be pretty inconvenient to do without a pressure gun, and amateurs have only begun getting into that approach with the Pressure Trace. Also, even if the amateur has the pressure test set up, the fact that bulk powder burn rate varies means that barrel time will change, and load tuning steps will have to be repeated for a new bulk lot that differs enough from the last one. Most handloaders don't want to go through that.
One of the lessons here is that if your surplus powder is not taken from pulldowns or has been tested by the supplier, it may never have qualified for the cartridge you want to use it in, so caveat emptor.