doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Pressure vs. Velocity

I keep reading posts about recommended pressures for vintage guns but I don't see them posted on cases or boxes of shells. Shell manufacturer web sites do not list pressures. I always see velocity listed. So if I am shooting 12 gauge Federal Top Gun shells or similar, 1 1/8 ounce with a velocity of 1145 fps what can I expect for pressures? I am shooting a Parker Trojan, Ithaca NID and an A.H. Fox Sterlingworth, all with 2 3/4" chambers measured with a Galazan chamber gauge. All are in good condition. Are these loads appropriate? If not what RST loads would you recommend for clays. I have no problem going to 1 ounce loads.

Also, what recommendations do you have for a good factory turkey load for the Sterlingworth F/F or the NID F/M?

Thanks.

Velocity and pressure do NOT have a direct correlation.

I would use this in #6 shot for turkey

http://www.rstshells.com/store/p/109-12-Ga-2-1/2-Lite-Roll-Crimped-Vel-1150-1-1/16-oz-Load-Box.aspx

12 gauge 1 1/8 ounce loads going out at 1145 fps.. sounds like a mild field/trap load. should be safe for the guns you list.

you may find that rst or polywad loads will be easier on your shoulder and your guns...particularly the one ounce loads. they are just nice to shoot.

Comparison of modern dense powders for 12g 1 1/8 oz. at 1200 fps (3 Dram. Eq.) in a Remington case with Rem 209 Primer and WAA wad from Alliant Powder http://www.alliantpowder.com/

Alliant e3 - 17.2 grains = 10,950 psi
Red Dot - 18.3 gr = 10,300 psi
Green Dot - 21 gr = 8900 psi
(Infallible) Unique - 22 grains = 8900 psi

Published independent testing:
3 Dr. Eq. 1 1/8 oz. Winchester Trap Load
1,202 fps @ 9,600 psi
AA Xtra-Lite 1 oz. WAAL12
1189 fps @ 8000 psi
AA 'Low noise Low recoil' 15/16 oz.
980 fps @ 6,200 psi

You have of course measured the wall thickness of the 3 vintage guns? And checked the head of the stocks for cracks?

Without pressure there would of course be no velocity. Pressure & velocity are thus directly related. What is so seldom mentioned & so seemingly not understood is pressure involves a Whole lot more than just the maximum peak pressure. Pressure as it relates to velocity includes the "Total Pressure" from breech to muzzle, or everything under the curve.
A higher pressure thus gives a higher velocity, but this "Absolutely Does Not" say the load giving the highest "Peak" pressure will necessarily have the highest velocity.

Thanks and well stated 2-Piper. I was about to call bullshit on the velocity/pressure non-related thing.
JR

Taken in the context of the discussion, there is no "bullshit" in this statement.

In discussions of shotshells when pressure values are noted, they invariably relate to PEAK pressure. Whereas the literature is awash in xxxx psi, lup and cup numbers, only in rare cases does one ever see a pressure trace revealing the total pressure (vs time) under the curve.

Therefore, in the jargon, shotshell pressure unless otherwise specified will always be taken to mean "peak pressure." The more astute readers in this forum would not be confused by, nor take issue with, the quote.

And our more genteel members here wouldn't add a back-handed insult to their otherwise well-explained counter.

My apologies to Skeetx for the "bullshit" comment. Poor choice of words. But I did agree with 2-Piper.
JR

Personally, I feel "An Astute" reader should confront a statement which is false in nature. Pressure "IS" directly related to velocity. True Peak Pressure is not the defining factor. I was though of the opinion this is a board dedicated to learning so I see nothing at all amiss in trying to get folks to look at pressures beyond the "Peak".

There isn't a whole lot of variation in pressure curves, even from black powder to nitro--although that old wives' tale was around for a long time. The Dupont graph from the 30's showed it wasn't true then, and Sherman Bell's pressure tests showed it isn't true now. Pressure drops quite quickly past the peak, which is always reached in the chamber. There is variation from one powder to another, but not really enough to be concerned with as far as danger from a pressure burst is concerned.

If you're looking for factory shells that are safe to shoot in vintage guns (assuming said gun is in good condition), you're in pretty safe territory if you go with shells designed for CIP "standard proof" guns. Most of those seen in the States are field loads rather than target loads, so you can reduce both pressure and recoil even more via reloading. Or you can go with shells from an outfit like RST, which will provide you with pressure figures.