Questions on an old Ithaca 12ga SxS

[Baxter6551]

Mr. 2152hq - so much great info thanks for sharing all that. Do you still work on the guns?
I have a 1924 Flues serial 391xxx field grade which I dated to 1924. Came with the canvas breakdown case and wood cleaning rod. Stock is dark next to frame from oil over the years but no cracks that I can see.
I hunted pheasants with it and shot some skeet over the years. Knew nothing about the shorter shell length and shot 2 3/4 shells without any noticed issue. Would lengthening the forcing cones be an improvement ?

 

[AJ]

Did not read all the previous postings. I have a Winchester Model 1912 (Model 12) made in 1918 and it is chambered for the 2 1/2 inch shells. I tried it once with 2 3/4 inch shells while shooting trap. The 2 3/4" would not extract properly. Fired another round with the 2 1/2" and it worked like a charm. Have had the barrel shortened to 18" and am using it as a house gun. Finish was shot and had a Poly-Choke (hate them) on it. Paid $87.00 at auction for it about five years ago. I keep a box of HST 12 ga. 7 1/2's for it.

 

[LostintheOzone]

There is no reason to believe that shooting 2-3/4 shells in a 2-1/2 chamber will be dangerous. That is a total myth.

In 2001 Sherman Bell did extensive testing of firing a large number of factory 12 gauge 2-3/4 shells with different loads in a 2-1/2 chamber (actually several different 2-1/2 chamber designs) as reported in the Double Gun Journal. He used an actual piezo gauge instrumented pressure test barrel. His results were that the average peak chamber pressure increases were negligible, between 300 psi and 1000 psi, depending on the specific load. It was also noted that shot-to-shot peak pressure variations were seen to be from 300 psi to 600 psi for identical loads.

Also, be aware that the actual fired case length of most of today's plastic shells, either 20 or 12 gauge, is closer to 2.6" than 2.75"

Personal experience, I have a very early 20 gauge Model 12 with a 2-1/2 chamber. I have fired thousands of 2-3/4 shells through it without issue. The only problem is the ejection port length. It is too short for Federal fired cases to clear. Remington and Winchester plastic cases are slightly shorter and eject OK. When I first got that Model 12, I started by cutting the case length of 2-3/4 cases to 2-1/2" for reloading. I fairly quickly stopped doing that as it was just a waste of time and effort.

There is no reason to believe that shooting 2-3/4 shells in a 2-1/2 chamber will be dangerous. That is a total myth.

Many people who shoot the old doubles and load their own 2 1/2" stay <9K psi. 11.5K is max Sammi pressure for factory ammo. The older British guns (pre war) were all proved to 3 tons, which was 8938 psi.

That's not to say that American guns weren't built for higher pressure but that would be pure conjecture because they were never tested for pressure.

I used to load my own 2 1/2" ammo because I had a few old doubles.

The problem with using factory 2.75" shells is all one really knows is the pressure is below 11.5K psi. It isn't the shell length so much as the pressure in a 2.75" chamber. Shorter chambers don't seem to increase the pressure much.

For anyone who believes it's OK to shoot factory 2.75" ammo in an old Flues, NID, or any double built before WW2, I say go for it. Personally I shot ammo I knew had lower pressure.

Not trying to talk anyone out of experimenting with an old shotgun, or a submarine.