Some bbls of equal lengths can shoot same identical load at different speeds ,why ? I have a 7mm wsm that shoots nearly 7mm STW speeds . Just today shooting 168gr Berger VLDs with bullet touching the lands 69.2 grs of Re#25 I was able to average 3250 FPS. No complaints of course just wondering why ? Its a 26" Brux bbl. 70.5grs of WXR pushed a 139gr SST at 3500 fps ( 3 Shots) but 100 yd group was greater then 2 MOA. 168 gr VLD shot under 3/4 MOA at 130 yds.