by orhunter » Fri Oct 09, 2020 1:37 pm
Some more stuff about velocity..... I don't know what pressure 28's are proofed at but 12's are 18,000 PSI. Maximum for everyday use is 11,500. When we look at loading data we see tons of loads that are nowhere near that pressure. Although the loads are generally accepted as maximum, in reality they're not because of pressure. They are simply the highest pressure tested for that powder. Pretty much all loading data including modern rifle cartridges are the same. Modern bolt action rifles can be safely loaded to 65,000 PSI. Doesn't matter if it's a .250 Savage or a .458 Lott.
One problem with shotgun pressure is it doesn't take much more powder to get a big rise in pressure. The faster burning the powder, the quicker a person can exceed pressure limits. If a person wants to play with this, use the slowest burning powder you think might work. Stay away from the fast stuff generally used for target loads. You'll also need a chronograph to read pressure through velocity increases. Don't guess. Make sure your loader is throwing the correct weight shot charge. Most don't, they're more than likely lite if set up for lead shot. Hard, high Antimony shot is lighter per volume than pure lead. When I was adjusting my Grabber for 1 1/8th oz., I had to open up the charge bar by around .020 to get the correct weight. I gained approximately 26 more number 7 shot per load. That's significant. When you start working at maximum pressure, you'll need to weigh every powder charge.
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