doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Low Pressure Question

Two Piper is exactly correct.

Alliant does not list loads under 7,000 psi for just this reason.

My experience with Red Dot is that it's not worth a crap under 8,500 psi. Certainly the current production Red Dot can't be trusted under that. It's at it's best with a 1 1/8oz load, a name brand wad, and a goodly charge. Clean and complete burns then occur.

Promo works better in light loads, at least for me.

Yep, I have also had 7625 squib loads in my 10 ga, so switched to Pb.

Pressure is pressure is pressure. The metal cares only for the thinnest wall between the breech and wad base at the instant of pressure peak. Depending on pressure decay and wall thickness as the wad moves down the barrel, it might well be that the maximum stress would be after pressure peak.

Is Promo powder something other than cheapo Red Dot?

DDA

Promo is a blend according to an Alliant tech via phone call when it was first introduced. Powder that didn't make the cut for canister grade as Red Dot or American Select or Green Dot is blended to the approximate performance of Red Dot without the density consistency. I've had good success with it. The density varies with lot, but then so does modern day Red Dot. I'm currently using a MEC 35 bushing to throw 19.5 grains of Red Dot (the stuff is fluffy) and anything less under 1 oz of shot won't burn completely. This powder is about three years old.

We shoot a winter skeet league here in northern Wisconsin, so we get plenty of opportunity to test loads in cold weather. I've switched to Extra-Lite pushing 7/8 oz shot in my vintage Brit 12. Pressure runs around 7500 psi, very clean-burning, no bloopers at all. Sometimes up to an ounce for some Sporting Clays targets. Powder charge is relatively light, in the 15-16 grain range, depending on the specific load. I'm a big fan.

Drew posted this link:

claytargettesting.com/study2/Study2.3.pdf

Looking at the RedDot/GreenDot pressure curve in the Clay Target article it convinces me that the pressure curve arguement is more academic than practical.

I've been shooting my Birmingham proofed LC Smith for over 15 years (850 BAR proof - 650 BAR service). I used 7625 and the PB early on but started shooting a 7/8oz RedDot load in Federal Paper hulls that list at 4800 PSI @ 1200 FPS. I'm a mild weather shooter so I've never experienced a squib load with it. Paper loads look so appropriate in the old girl and I even sneak a sniff occassionally.
A 1oz 700X load at 5000-7000 PSI (depending on primer) feeds all my SxS's.
In my original post the term "hogwash" might have been a little strong.
Craig AKA nitroproof

Craig, in the specific case of your gun, "hogwash" may not be too strong. Your gun's service pressure is not far off American SAAMI standards with an 850 bar proof. 650 bar service is right around 10,800 psi, so you don't have much to worry about at all with reloads, even building in a reasonable safety cushion.

Note: 650 bar does not come out to 10,800 psi if you use the 14.5x formula to get psi. However, per the Birmingham Proof House, under that system, those were bars as measured with the old lead crusher system. They converted to psi equivalent to get the 10,800 figure.

Mr. Brown-

So if 650 BAR = 10,800 then my gun was proofed at over 14,000 PSI? It still won't get any Wally World Federals!

Craig

Short version until Bro. Larry responds:

650 bar is standard CIP (British and European) service pressure for shells designed for guns proofed at the CIP standard of 850 bar

European (CIP) proof pressure of 850 kg per sq. cm. (BAR) = 13,920 psi proof pressure = 10,730 psi service pressure (SAAMI)

Craig, Drew has the exact service and proof pressure figures. No, I would not feed it standard American factory ammo either. However, you do have more room to work than with some of the older Brit/European guns.