Greetings All,
It has been all hot and horrible here in Hawkes Bay for the last few days and I have been hiding from the sun and doing some research. My dearly beloved calls it something else. I subscribe to loaddata.com and while looking for something else I stumbled on data for the .303 developred by Brian Pearce. Brian does the Pet Loads reports for Handloader these days but the data I found is only published on the web site. Brian usually starts low and gives a series of chronographed loads which are most helpfull for those of us who use a lot of reduced loads. Anyway I compared his loads for the 174 grain projectile with the Hodgdon data and my results. It was imediately apparent that Brian's results gave a lot less velocity for the same charge, about 200 fps less! My loads were somewhere in the middle for my two groove barrel and close to Brian's in my five groove barrel. In my two groove barrel two different lots of Hornady 174 grain Round Nose projectiles gave velocities 120 fps apart with all other components the same. This showed up on the target as well. I have noted a change of shape on recent Hornady projectiles with a sharper junction to the ogive. This places the ogive of the later projectiles closer to the rifling and apparently increases velocity and no doubt pressure.
.303 rifles have an extremely wide range of types and dimensions of rifling. Add to that differing levels of wear and erosion then wide variations in velocity should be expected. All we can do is to chronograph a mid load and work up to a reasonable and below max velocity. I looked at some older load manuals and the loads they had scared the crap out of me. Their start loads for the same projectile and powder were above the max loads in most current data.
Regards and take care, Grandpamac.
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