Many of you do know, but for those of you who don't, here goes. From the Accurate Reloaders Guide 2005 some info. The formula for recoil: mass of bullet or shot + wad + powder x velocity = recoil. Pressure is NOT mentioned in the formula. So don't think for a second that because a load doesn't kick it is a low pressue load. A couple of examples:
7/8oz 1200fps - Clays powder - 8900psi
7/8oz 1200fps - IMR7625 - 4400psi
1 oz 1200fps Clays 10,100psi
1oz 1200fps Solo 1250 6400psi
1 1/8 1200fps Clays 12,000psi
1 1/8 12oopsi Solo1250 6600psi
Those were the highs and lows that I found in the guides I had. Now I'm not worried about blowing one of my guns up by shooting factory loads, but I wouldn't want to shoot a nice SxS loose, so I shoot " low pressure" loads.
I have blown-up a gun, but that was my fault - wrong powder. Now for black powder loads. They kick more because there's more powder, hence more weight in the above formula - not more pressure. A 3 dram load by volume is 82grs [ about 75grs weight with my measures ]. If a modern shotgun reload is around 20 grs of powder, then the BP load weighs 55grs more: or about the same as going from a 1 1/8oz to a 1 1/4oz load. Now that's gonna kick more. From the Lyman BP Guide a 3 dram 1 1/8oz load is 5000LUP, or about 5500 to 6000psi. A 3 3/4dram load is 5900LUp, or 64-6900psi. That's still a low pressure load that kicks pretty good.
One more thing - I don't believe you can say what's a safe load by shot column height with todays modern powders. One would normally think a 1oz load is a light 12ga load with not much pressure. But as you can see from the above example it can exceed 10,000psi, and a 1 1/8oz can go 12000psi.
I guess I'm trying to say, and clear up is that there can be high pressure with out much recoil, and like with BP there can be a lot of recoil and low pressure. And the height of the shot charge does not dictate pressure. I approve this message
- Paul