Hey 1911,
Here is a slightly different take on this.
I can totally understand why you snatched up that Remington for $200, and I can totally understand how, at that cheap price, you would have initially thought that you could use that action to create a reasonably priced long-range shooter in a different (perhaps magnum) caliber. Probably everyone over 50 on this board thought the same thing once upon a time, way back when, when we were younger.
But, what I think everyone is telling you is that we were wrong, and we are trying to save you from the same frustrating, expensive mistakes. Your rifle was specifically engineered for the .30-06, an absolutely perfect long range tactical round. To take this piece of finished engineering, and try to make changes to it to convert it into something it is not (such as a .300 Winchester Magnum), will require lots of money, bolt alterations, and frustration, all to end up with a rifle that may or may not shoot well, after spending hundreds of man hours and very likely well over $1,000.
In common vernacular, this is called "re-inventing the wheel." We have all done it, and we all regret it!
Here is the best advice I can give you.
1. If you want a .300 Magnum, then take your current rifle to a large gun show, find a used Remington 700 in .300 Magnum, and trade your current rifle towards the price. With some good bargaining, you should be able to get $300 in trade towards the Magnum, and you should only have to throw in another $100 in cash to buy it. Presto, for $100 in extra cash, you have instantly acquired your Magnum action and bolt, without spending $400 in bolt alterations and without waiting 4 months for the gunsmith to do the work. This same advice would be true for any standard magnum caliber, including the 7 Mag, or the .300 Winchester Short Mag.
(Personally, I can't imagine why anyone would consider any magnums other than these 3 standard calibers for a long range tactical rifle.)
2. If you decide to go with a short action round, then go with a round that is either the .308 Winchester, or a derivative of it. Go to the gunshow and trade for a Remington 700 in .308 Winchester or .243 Winchester (very very easy to find). (By the way, the .308 Winchester is a superb long-range tactical round.)
3. If you decide to stay with the current action, then stay with the .30-06, or a .30-06 derivative round (such as the .25-06 or the .270 Winchester, or the .30-06 Improved etc.) I am not sure where the .280 Remington fits into this mix, but I believe you could easily convert your .30-06 to a .280 Remington as well.
By following the foregoing parameters, you are going to save hundreds of dollars, and lots of headaches. The money you save can be put towards your new barrel or stock. And also remember this, when you get complicated gunsmithing work done, there is better than a 50% chance that when you get the rifle back, it will NOT work as nicely as you expected, and you will be taking it back for more tweaking (which results in more waiting and often more expense).
I hope that this info is helpful to you.
Regards,
Mannyrock