Re: Vihtavuori Powder
The other thing about Vihtavuori Powder is finding it at your local dealer. While a good powder it apparently is not nearly as popular as most American distributed powders and that makes it hard to find locally.
There are a ton of different powders that work well with 9mm and 45ACP. Probably one of the most universal powders that can be used in almost any handgun cartridge is Winchester 231 or its exact twin Hodgdon HP38 (same powder different label... Hodgdon distributes both). I use W231/HP38 in all my handgun loads.
These fast powders like W231/HP38 use up a small portion of the volume of the case and that is alright for them. They are designed that way. Some other slower burning powders when loaded down, using only a small part of the case volume, are affected by the excessive empty space. The velocity results are different depending on where the bulk of the powder lies in the case. This appears not to be true of the fast buttoning powders like Bulleye, W231/PP38, AA#2 and others. The slower powders in the burning speed range of Unique (but not necessarily Unique???) may be greatly affect by powder position in the case. Velocity testing will point out which is and which is not.I have yet to see an article on this matter but have read comments where in-promt-to testing reveal this issue.