Will somebody please do ballistics tests with every other possible bullet that could have been shot out of that gun..?
That would take a hell of a lot of time and money for very little return. And there's no guarantee that some imaginative person couldn't dream up a way to make it shoot something else that you didn't even think of. Besides, cartridges can be custom hand-loaded with any amount of powder that'll fit, which almost creates an infinite set of possibilities by itself (not that loading the round with 0.0002 grain less powder will make a real difference).
Lone Star boy was reaching for the sake of arguing with me. But he opened the can of worms and won't explain himself, so I guess I'll clean up after him. I have an old .22 bolt action carbine (or rather I did, before the boating accident) that shoots .22 short, .22 long or .22 long rifle with equal ease, with no modification. That's because all three types slide into the barrel right down to the lip at their butt ends. But even though the projectile will fit through the barrel just fine, it can't fire .223.
.223, on the left, has shoulders. The entire cartridge won't fit in the barrel, so the bolt with the firing pin can't close with that round in the way. A bolt action rifle designed to fire .223, or .30-06, or .30 Winchester Mag or any of those high power rounds with shoulders like that, close with their firing pins much farther from the end of the barrel, so they can accommodate a round that won't completely fit down the barrel. They have to be designed to put the firing pin in the right place, away from the end of the barrel.
When our argumentative redneck went shopping for sleeves, he came up with something weird and arcane that basically extends the barrel back inside the gun. This holds the kind of round (like .32 or .30 Springfield) which is designed to slide all the way into the barrel, back where the firing pin can reach it. I won't use one because if it isn't aligned perfectly with the barrel, the bullet will get stuck and instead of propelling it out the powder will explode the gun in your face. That's how esoteric he's getting. That's how far he's reaching. We're talking difficult and potentially dangerous stuff for no performance gain at all.
Basically you already know what all the ready-made, widely available .30-06 rounds do already. For anything else under the sun, you have to ask yourself, would this 22 year old video game addict even think to try it, and why would he?