Interesting. In separate publications both Parker Bros. and AH Fox
state that complete or better progressive powder burning is achieved
by using shells that are slightly longer than the actual chambers.

In actual usage, many 2 3/4 shells are fired in 2 5/8 " chambers. I would not
attempt that in damascus barrels, however.

Since this thread was running back in 2017, two different late Remington CHE 12-gauge, 3-inch guns have been on the market -- 241442 with 32-inch barrels on a 2-frame with an unstruck barrel weight of 47 and 241838 with 32-inch vent rib barrels on a 1 1/2 frame with an unstruck barrel weight of 413.

Measure your un fired 2 3/4 " shells . They are less length. so are ok for 2 5/8 chambers in 12 ga.

Charlie, my Lefever sleeved mag ten handles as well as can be expected. It was originally a twelve that lettered as a ten pound three frame.

bill this is a 3 1/2 inch gun is it....whats the chokes on this gun...wish I lived closer to you to take a look at this gun of yours....have you ever hunted ducks with this gun... my 3 frame 12 weighs around 10 LBS its unstruck barrel weight is 5 10 it has 3 inch chambers but not marked as such...my gun is choked modified and full and it is a twist steel barrel..i ve used in in duck hunting a few times went one hunting up in missori one time killed one goose with it and some ducks....these 3 frame guns are neat...but even with the weight they have a 3 inch shell still kicks pretty good..... charlie

Charlie my 3 frame DH 12 gauge has 34" Damascus barrels with an unstruck weight of 6 lbs 8 oz. If memory serves me right the barrels finished weight was either 5-8 or 5-9. Special instructions were to chamber 2 7/8, and to shoot #4 or #5 shot. No distance, no pellet count, just that info.

boy that 3 frame has some heavy barrels...it has the most heavest barrels on a 3 frame 12 ga I ve heard of...I really like these guns with long barrels heavy weights...must have been a water fowler that ordered your gun...what chokes do you have in this gun....I never tire of talking about these big guns...charlie

Chokes are tight at .036 and .039. I shot wobble trap with it Tuesday night and can definitely say it is capable of absolutely crushing targets with 1 oz of #8's. Shot 1 round where we only had 3 shooters and the darn thing was starting to get a little heavy. Ordered with a requested weight of 10 to 10 1/2 pounds and holding tight today at 1 oz under the 10 lb mark.

yes sir that gun of yours was built to shoot long range and with heavy loads...charlie

The length of unfired shells is not what is important in the discussion of how long a shell was meant to be used in a chamber. It is the fired length that matters. When the crimp unfolds, if it goes too far into the forcing cone, it becomes a restriction to the forward progress of the payload, and tears at the case mouth. Pressures rise significantly when that occurs.

That said, most 2 3/4" shells I have measured don't even measure a full 2 3/4" when fired, which is what actually matters. They don't protrude far enough into the forcing cones to be a problem. Each person should measure for themselves to determine this, on the load they are interested in using. Just because most of them are short enough doesn't mean all of them are.