doublegunshop.com - home Forums Thread Like Summary - Need some help with nitro proof and shell loads...

I’m looking at the nitro proof on a 20 gauge I recently bought and am curious about what loads it can—and cannot—handle. With a 20, of course, you have a variety of load options, and I often use 2 3/4” shells with 1 ounce of shot. What’s the best way to know if that’s good to go with this gun?

The gun was re-proofed to 2&3/4" after the time that shot charge was part of the proofs. Originally a 2&1/2" gun I'm sure but an inquiry with H&H would confirm. I would shoot light loads in it most of the time myself, though I'm sure it would be fine with occasional 1 oz loads. CIP 2&3/4" cartridges operate at a fair bit lower pressure than our SAAMI cartridges.
Steve

What does the gun weigh?

The accepted formula is that you need 6 pounds of gun weight for every ounce of shot in the cartridge.

If you match the load to the weight of the gun, it will be kinder to both you and the gun if you use that as a maximum shot weight.

Remember, less can be more and a lighter load may keep you on target if you are not being knocked cross-eyed by the recoil of too heavy a load.

Vic,

All of the European ammunition and most shotgun ammunition manufactured by US companies here are CIP compliant and each box will have the mark of the proof house that tested the load.

Look for the "inspection of ammunition" proof mark on the box - they start on page 7 of this document https://www.anarma.org/media/kunena/attachments/1233/genco_en.pdf . The most common I see on US ammunition boxes are Birmingham, Liege and Munich but I have seen others.

I would have no hesitation shooting US made 20 gauge cartridges with 7/8 ounce of shot at 1200 fps or less in a nitro proofed gun. My only concern shooting 1 ounce CIP compliant loads would be recoil damaging the stock not a pressure issue; recall that recoil is mass of ejecta and velocity related and has nothing to do with pressure.

I use 8,000psi as my default British proof 20 bore loads in both 2 1/2” & 2 3/4”. Remington 20 hulls are 2 9/16” so I no longer trim them to 2 1/2” but I do for the rest. It all comes down to being certain that every shell I have is safe to shoot I every gun. I could go up to 9,500psi and still be safe but I do not for two reasons. Old wood cracking is more of a concern than barrel failure. The second concern is shooting 2 3/4” shells in 2 1/2 chambers would result in slightly increased chamber pressures so I err on the safe side.

I think the likely problem comes as a result of recoil, and pressure isn't a significant factor in recoil. Velocity and shot charge determine recoil. I've owned modern Webley and Scott 20's made for export to this country. Often weighing less than 6 pounds, and some of them with 3" chambers. My concern shooting an American 3" 20ga in those guns wouldn't be pressure, but rather how the recoil would impact me, on the back end of the gun. And what it might do to the stock. I've looked at those guns and thought to myself: "Someone might be crazy enough to shoot magnums in them . . . but not me!" I'd be somewhat hesistant over standard 1 oz 20ga target loads, like Winchester's AA Heavy Target Load. I wouldn't worry about standard 7/8 oz skeet loads. But as noted above, Claybuster's 3/4 oz wad makes loading light shot charges a piece of cake. And they break skeet targets just fine.