Beemer,

All canister grade powders are blended from different lots to acheive very specific characteristics. Even if there are 55 gr of 4064 that is only 1.5% if the ratio is what you indicate. Mix it up good and use it, the difference in performance will not be noticeable.

Adding a slow burning powdr to a faster burning one does not create a safety issue, adding a faster burning one to a slower powder does, or can, depending on how much there was.

To answer your first question, all IMR brand powders are extruded. All powders manufactured by the current IMR Company are not. The brand IMR has existed for over 100 years through several manufacturers.

It is the same as Bullseye. It has always been Bullseye whether manufactured by Laflin & Rand, Hercules or Alliant. Bullseye is the brand, The listed companies were/are the manufacturers.