Has anyone tried 2 3/4 12 gauge 2 oz TSS?

[BandedSpur]

Maybe somebody can explain to me how Apex's 2.75" 2oz #9 and 3.00" 2 oz #9 have the same advertised muzzle velocity (1200fps). I would have though carrying the same shot amount in a shorter shell would have taken a loss in muzzle velocity. Somebody care to explain?
Also, for someone that has shot both, is there a difference in recoil?

The SAAMI pressure limit is the same for 2.75 and 3" 12 ga loads. (It is significantly higher for the 3.5" gun). One could theoretically run the 3" load faster than in the 2.75" shell due to more room in the hull for cushioning, but there is no real advantage in doing so with TSS. I load all of my 12 ga TSS loads at 1100 fps, from 1.25 to 2 oz of shot. TSS 9s at 1100 fps have the pellet energy to kill way further than I will shoot, so stepping on the gas does nothing but add recoil and wear on the gun. Also, loads at 1100 fps are subsonic and should theoretically pattern better than faster loads. Whether that is true in practice is debatable.

Now if you were to compare a 3" 2.25 oz load to a 3.5" 2.25 oz load, you could certainly push the load faster in the 3.5" shell, because of the significantly higher allowable pressure - 14,000 psi for the 3.5" shell vs 11,500 for the 2.75 and 3" shells.

Recoil from a 2 oz load at 1100 fps from my 8.75 pound 1187 is not bad at all. But it would be pretty stout in a lightweight fixed breach gun.

So if you opened the Apex 2.75" shell and Apex 3" shell, what is the difference if there is the same amount of shot and powder? What is the advantage of going to the longer shell?

The powder could be different, the wads are probably different, the spacers/fillers will be different.  There is no advantage to longer shell, unless you go 3.5" and jack up the speed because you like recoil. The advantage goes to shorter chell because it will function in 2.75"-3.5" chambers.

Another excellent explanation. I agree that there is no real advantage to the longer shell.