The 264 win mag brass is only .006" longer than the 3006 brass
so it will work fine in a 3006 length action.
If you already have a 3006 then your smith will have to open the
bolt face from .473" (3006) to .532" and change the extractor
plus open the rails for the 264 win mag.
If you can find a long action rifle with a magnum bolt face (.532)
then it would be a simple barrel change.
And for extended barrel life I would recomend a stainless barrel
as large as you can stand starting with a #4 and going up #5,
#6 and a #7 (They heat up slower and dampen better).
As to brass life of a belted case, If you intend to reload the brass
more than 3 or 4 times there are several things you should do.
First have the smith chamber with the minimum head space .000 to .oo1max.
Then stay away from MAX loads.
And neck size only.
I have a lot of the belted cartrige rifles including the 7mmSTW,30/338,30/378
and the 416 rem and have good brass life on all. (Note' dangerous game
cases need to be full length sized so there are no surprises).
I can remember when if you did'nt have a rifle with a belted case you were
considered poorly equipped. (A Woose).
What I do like about the big belt'less case,s is more case capacity for the same
basic case size ,like the 7 STW and the 7RUM.
My first deer rifle was a 6.5 - 06 Ackley Improved! My dad loaded it with 100 gr SP's. Very mild kicking little gun. It was built on a 1917 Enfield action with a 26'' barrel. Not sure what contour it is but it is a lightweight one. Whole rifle weights right around 7 1/2 pounds.
It shoots sub moa at 100! And will shoot a 2'' group at 4-500 if I do my part......
So I highly recommend it! Even if its just a straight 6.5 - 06.
It's a fine cartridge, and a great round that you can load with a light boolit!
Is this a gun that you still use? I hadn't thought about an ackley imp 6.5-06. I would guess that it would be fairly equivalent to the .264 win mag. What you described is what I have been imagining, light bullets now, heavier later.
You don't have to change the chambering as 6.5-06 is great though a new SS 1-8 or 9 twist tube in a #3 or 4 contour would help. Many older guns weren't of a fast enough twist. You want to start your son off with 100gr. Partitions and as he grows and the game gets larger you can go to 125gr. Part or 130gr. Accubonds. If in the future larger game is on the menu, there are 140gr Part or A-frames ready. Just make sure you match a good barrel and someone who knows how to install one, not do a plumbing job(no disrespect to plumbers, just respect to good smiths).You will only be giving up 100-200 fps and gaining a much easier time downloading for loads when starting out. Just MHO, enjow the time with your son.
Steve I have owned the 6.5x06 and shot the Ackley version. I would not fool with the Ackley version. My 6.5x06 was a great performer however I shot it with only heavy bullets like Berger 140 VLD. If your son can handle the 7mm08 then he should have no issues with the 6.5x06.
As stated above the 280 might make a better choice a simple rebarrel with factory ammo available, better bulllet selection, and the ability to go heavier for larger game if needed.
Did some digging and found that in the 6.5-06 the imp version only helps in the largest bullets available, 160gn or bigger. So, I'm not going to bother with the imp version. Why fire form brass for little or no gain. We will play w/ different grain bullets durring break in. Am planning on using the 130 Siroccos for hunting this fall, unless the recoil is too much. I don't think this will ba a problem since he has shot the 7mm-08 w/ 140's with no adverse effects.
We went with the McGowen 24", #4 taper, 8.5" twist, ss fluted.