You would get similar velocity to the 22-284. Example of what you might get from this article:
http://forum.accurateshooter.com/threads/22-284.3767921/
They mention a few things:
"I had one (22-284) chambered in a 28" Lilja for a while and after 500 rounds the barrel was pretty much toasted, from shooting the 80 SMK's with their little asses on fire. It would shoot around 2 inches at 500 yards no problem."
"As near as I can remember the 80 gr SMK's were just shy of 4000 fps.
I also tried a few 80 gr Bergers but they turned into dust about 25 yards out"
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Sniper' hide has another thread on the 22-284:
https://forum.snipershide.com/threads/22-284-project-loading-data.2448/
"Sounds like you have some good ideas. As for your twist/bullet selection- I do not believe the 55gr's will survive a 1:8 twist. I expect they will simply explode upon exit- I am 100% certain a 35gr will not survive. I would think you should be able to push the 80gr close to 3600 depending on barrel length and powder selection. Considering you would like to use the heavy bullets your best bet for powder might be Retumbo with RL-25 in second. RL-22 is a bit too fast and US869 is too slow. Cant hurt to test them all."
Don't be too concerned about barrel life. You own the reamer and can set the barrel back once at least. So if you got 750 rounds before the accuracy drops off you will get another 750.
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While you could do it the barrel life will be short. Extra costs for custom dies and reamer. Would be better served to go with the 22-243 middlestead or similar well established cartridge. Or quite frankly make a 6mm-284 at least you can get 1000 rounds out of the barrel. I know that is how long my 5R 1 in 7.5 Bartlein lasted. Set it back and rechambered myself shooting it again.
If this is something you want, do it. I made a 6mm-264 win mag ONCE and that was enough of the super overbore chamber experimenting for me. When you make it be sure to post your results here.
