Interesting about the 150 mm barrel. The CIP specs are all about proofing and specify a standard twist but no standard barrel length. Unlike SAAMI, they have no standard velocity ranges for bullet weights, so they may not care about it. I looked up 45 Auto in QuickLOAD's table of test barrels, and all the labs listed there use 150 mm, except Keil, Germany, which uses a 200 mm barrel. I don't know how they came to choose that number over 127 mm, but it may have something to do with some particular guns the Europeans commonly chamber for 45 Auto.