I have a couple of boxes of S&B .303 Brit I got to try out in my No. 4 MK 1 rifle, but haven't gotten around to testing yet. I'll make sure to chronograph some of this ammo, to see if that shows us anything. With same bullet weight, same sight setting, etc., a noticibly lower strike on target often indicates a higher velocity. I believe the theory is that higher velocity = less barrel time = less barrel rise to "normal" path of bullet flight.
I worked up a load with Sierra 180 Spitzer soft point to about same velocity as a clean lot of MK VII ball 174 gr. military--Right at 2400 fps--and it strikes to practically same point of aim. The Winchester white box ammo from the mid-80s tends to shoot slightly slower, yielding a slightly higher bullet strike.
I'll put this testing on my "things to do" list and post the results.
What model (Number and Mark) enfield are you shooting?
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Blog: Expert Witness