Here's an interesting study by Tom Armbrust on the effects of primers on velocity and pressure

http://www.armbrust.acf2.org/primersubs.htm

Interesting article. I especially liked the last two sentences. After doing as much or more patterning work than most casual shooters I can personally attest to the wisdom of those words.

+1 on Mr Armbrust's article. It is a fine quantitative analysis. Thanks for posting the link. v/r rch