One thing I find interesting is that average consumer/shooter has an idea of projectile velocities that doesn't have a lot of correlation with the real world. It's not their fault, because it's entirely encouraged by the ammo manufacturers. (It's why I joke about "Velocity as measured at the cartridge box flap".)That particular batch of Ranger-T, with a ~40fps velocity spread across a ten-shot string, was actually pretty consistent, especially for +P+ ammunition. (High pressure loads in 4" and shorter barrels can be a crap shoot. Is everything gonna combust good before the bullet leaves the barrel or not?)
As a for-instance, I have here on my desk a box of Winchester's 127gr +P+ Ranger-T ammo. Winchester's web page says its velocity (out of a test fixture) is 1250fps at the muzzle and 1236fps at five yards. I measure pistol velocities at nine feet from the muzzle, and when I chrono'ed that lot out of my M&P it averaged 1206fps over a ten-shot string, with a velocity spread from 1190fps to 1230fps. Adding a quarter or half inch of barrel length might boost the velocity...by an amount small enough to get lost in the statistical noise.
Mr. Boberg's written reasons behind the [XR9 pistol] design (increasing velocity in hopes of better expansion from 9mm bullets) always struck me as a very...well, simplistic grasp of terminal ballistics. "I will add .5" of barrel length which will add 25fps of velocity which will increase damage by 1d8+1" when all of it is just picking fly poop out of pepper.
By way of comparison, .357SIG 125gr Winchester Ranger fired out of my M&P357 had a velocity spread of nearly 80 feet per second. You could... and I did ...fire two rounds of RA357SB from the same box of ammo loaded into the same pistol magazine and have one doing barely over 1300fps and the next one moving just shy of 1400.
Obsessing over 50fps is a waste of time, in my opinion.
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