I have 2 Win M70 SS Classics in 300Win. One has the factory 26"bbl, the other has a BOSS bbl that I cut back to 23". Doing some load tests w/R-26 last week there was a 25FPS increase in the 26" rifle vs. the 23" rifle. Same FL size brass with the same number of firings, same primers, same 3.34" seating depth to match the mag box.
The 26" rifle has considerably more rounds through it than the 23".
Using IMR 4831 and 200gn TSX, the difference in velocity between the same 2 rifles identified above is under 10FPS using a LabRadar multiple times over the course of ~50 rounds through each rifle.
I hope this clears things up.
