Like Chinook I'd recommend Ballistic Products. Plus I've heard good things about Old West Scroungers ......
You might also try to fin some old reloading data in some of the old reloading manuals. In them you will find 2 7/8in data for the 10gauge.
But have you considered other possibilities?
Why not buy 3 1/2in hulls - and cut them at 3inches? Or even 2 3/4inches?
You can buy 3 1/2inch hulls from Ballistic Products along with a tool that will help cut them (quite accurately and SQUARE) at whatever length you want. Works well for other gauges as well.
When reloading the shell length isn't as important as the amount of shot in the "shot charge", along with the "wad column" and if those items are put together "well."
Then driven at an adequate and proper velocity through a well-choked barrel ...... will give you the performance (patterns) you're seeking.
With a 2 3/4in or 3inch 10ga hull you can probably get as much shot (carefully and properly) packed into that hull you need to kill pheasants or grouse or turkeys!
1 1/4 ounces, or 1 5/8oz is probably all the shot you'd need to hunt upland birds with your TENNER! If a 2 3/4in hull was too short - would surprise the heck outta me! But by buying and cutting hulls to your needs you'll find out quick what length is best for you ..... 2 3/4," 2 7/8," or 3 inches.
Plus 3 1/2inches is probably handy for stuffing waterfowl non-toxic shot into! ......
Good luck.
