Loading 20ga 2 1/2 inch
 

Just wanted to share these finding with anyone looking to load 20ga 2 1/2 inch shells. I measured 9 20ga hulls with the following results.
RST PAPER 2 1/2 INCH 2.537 INCH
RST PLASTIC 2 1/2 INCH 2.550 INCH
WIN AA HS 2 3/4 INCH 2.610 INCH
FED TOP GUN 2 3/4 INCH 2.615 INCH
WIN OLD AA 2 3/4 INCH 2.646 INCH
WIN HIGH BRASS 2 3/4 INCH 2.670 INCH
REM TARGET 2 3/4 INCH 2.672 INCH
REM STS 2 3/4 INCH 2.690 INCH
KENT FAST LEAD 2 3/4 INCH 2.709 INCH
First RST shells are not 2 1/2 inch, the new win AA HS are real close to RST lenght so I have started to use them in 2 1/2 guns with great results. You can load them with 3/4 oz , 7/8 oz and 1 oz. As you see non of the 2 3/4 inch shells are 2 3/4 inch.

To quote Gomer Pyle: "Golllllie!"

No ill intended, but these measurements have been such for a long, long time. Same with most 2 3/4" 12-bore hulls. This is why I have shot unaltered "2 3/4-inch" hulls in ALL my 2 1/2-inch chambered British guns for decades without the slightest problem or issue.

Sherman Bell investigated this years ago and reached the same conclusion.

But... if you want to have fun cutting hulls back and making 2 1/2-inch cartridges, have at it. I'll be out shooting on the clays course while you work away.

Yes, I know that many people have been shooting 2 3/4 in shells in 2 1/2 inch guns but when I tried it in a 98 year old 20ga LC Smith the new Win AA HS shells show no sign of damage, while the factory Kent and factory Polywad for instance had the front part torn off, not much but still it has to bump up the pressure some. So to be on the side of safety I would use the shortest shell I could find and those Win AA HS hulls are real nice to load, I just buy them new in skeet loads and shoot them up at the skeet range and I have once fired hulls for hunting loads.