With our rifle thing,your preference is reason enough. You do things any way you want.
I'll agree a MK 10 is a good receiver.
If I may ask,how does it shoot? If it does not shoot.proceed!
But since you mention a slim budget,there are good hunting bullets between 165 and 180 gr that have darn good ballistic coefficients.(Example,a long range Accu-bond.) I can generally find what I need at Nosler.I like their loaddata with their bullets.
You might notice with IMR or H-4350,or RE-19,you can get some pretty respectable velocity.
Both the 270 and 280 are great hunting cartridges..you can't go wrong with either...
If you go to the Hornady website,they have a ballistic calculator you can use.
Look in the load manuals and come up with achievable BC's and velocities for 270,280,and 30-06.
Plug in a 250 or 300 yd sight in,and run the numbers to as far as you want to shoot.
I'm not saying the 30-06 is flatter. But see how much you gain.
If you are going to use the Max Point Blank system,you might find the actual increase in "MPBR" is not that much.
These days,folks are relying less on MPBR,and more on ranging and correcting,either via knobs like the Leupold CDS,or reticles like the Boone and Crockett.
Once again,do it your way,but if that rifle is accurate,and you are on a budget,consider the barrel dollars could be premium scope dollars.
Good,precise optics will out perform "flat shooting" at longer ranges.
And the 30-06 with efficient bullets is no slouch.
There are a number of choices for barrels. Considering gunsmith labor costs,Lothar Walther has some practice at making a pretty darn sweet pre-threaded,short chambered Mauser barrels of mid range cost.This will give you an idea.
http://www.lothar-walther.com/drop-...ter.270win-mud.650-l-25.59-cr-moly-steel?c=66
Update: ! went to Nosler's site. For the 30-06,the 168 gr LR Accubond has a BC of about .525,and the 270 will shoot a150 gr LR Accubond with a BC of about .590. Muzzle velocity (max) is a nearly identical 2900 fps.
Yes,the .270 has the advantage.If you sight in a 300 yd zero for both cartridges,the .270will drop about 3 inches less at 600 yds.(51 vs 54 in or 1/2 MOA) Whether that is worth the price of a barrel is your decision