I've pushed handgun ammo past max before, on 9mm and 45, but I've never really pushed rifle past max. My theory has always been "whatever it hits won't care if it's going 100fps slower".
But on a recent test of 300 Win Mag on load development, I found my best load of 26 lots tested, sitting at a charge of 69.8gr of H4831SC w/ 220 gr Sierra Match kings. Sierra lists that as the max charge for that powder / weight / bullet combination.
I'm seating my Sierras longer than the book, by .108", which gives me a little additional capacity; and that "max" charge doesn't show any signs whatsoever of overpressure. Primers are still rounded on the corners, not set back, no detectable expansion of the web area, etc.
With the "best" group being at the high end, I'm tempted to push forward to see if it tightens up further.
With the background out of the way, my question is;
What increment should I use for testing beyond listed max on a case this large?
1% increments would be about 0.6 gr, 0.5% increments about 0.3gr (rounded down).
With H4831SC being resistant to temperature changes I'm not nearly as worried about load development in the winter / early spring and shooting in the dead heat of summer, as I would be with other powders.
But on a recent test of 300 Win Mag on load development, I found my best load of 26 lots tested, sitting at a charge of 69.8gr of H4831SC w/ 220 gr Sierra Match kings. Sierra lists that as the max charge for that powder / weight / bullet combination.
I'm seating my Sierras longer than the book, by .108", which gives me a little additional capacity; and that "max" charge doesn't show any signs whatsoever of overpressure. Primers are still rounded on the corners, not set back, no detectable expansion of the web area, etc.
With the "best" group being at the high end, I'm tempted to push forward to see if it tightens up further.
With the background out of the way, my question is;
What increment should I use for testing beyond listed max on a case this large?
1% increments would be about 0.6 gr, 0.5% increments about 0.3gr (rounded down).
With H4831SC being resistant to temperature changes I'm not nearly as worried about load development in the winter / early spring and shooting in the dead heat of summer, as I would be with other powders.