Reloading .303 British : Effect of Primer Selection on Muzzle Velocity

Oddly, I’ve never found this to be the case Shamu. And that experience is with numerous rifles and many thousands of rounds. 

For example, here is the plot sheet of the first ten shot group with the T last Saturday. The bore had been cleaned down to bare steel with C4.  I shot this group as a “warm up” at 300 yds prior to running the bullet seating test at 600 yds.

First shot was nearly dead center. The first flier did not appear until shot #6. And it was the highest velocity in the string, shot #2 was the lowest.  The second ten shot string at 300 was about the same, although a higher velocity ES of 70 fps.  I then shot one ten round string at 600 to confirm scope settings prior to shooting the 30 round bullet seating test. The barrel didn’t settle down until the last 10 shots of the 30 round test, a total of 50 rounds. 

This was the third 10 shot string shot last Saturday, at 600 yds. Note the similar shot #6 flier. This occurs about one in 10 to 20 shots with this rifle. It’s usually the highest velocity shot in the string, but this time it was the third highest.  I shot this group to test the effect of pulling the rifle firmly into the shoulder vs a very light pull.  I alternated shots with a firm pull and light pull. I saw no correlation of muzzle velocity or POI between a firm and light pull. No sling, shot off a front bag rest. 

Occasional shots in the 3 MOA diameter 9 ring at 600 are going to occur with these rifles. Very few vintage sniper rifles and shooters can hold the 600 yard target 2 MOA 10 ring for 10 shots. But it’s those 8 ring shots I’m trying to eliminate. I’m gonna get there one day…