AFAIK, no one has tried to make an AR upper in 7mm Magnum
NO!!
7mm Magnum and 300 Winchester Magnum
NO, doubt it would even seat completely in. The base of the 7mm magnum (case before neck) is longer then a 30-06.
243, 270, 30/06, 7mm Magnum, 300 Magnum
no even though the projectile (Bullet) is the same diameter and weight, the cartridge cases are very different, the 7mm rem mag is a belted magnum, and is larger in length and diameter than 7mm mouser cartridge. in other words the 7mm magnum is too big to fit in the M24's chamber
You will have to define what "accurately" means.
Define 7mm. Do you mean 7mm Mauser ( a little less than 30-06), or 7mm Magnum, (a bit more than 30-06)
I have had personal experience with both cartridges but I have noted that my 7mm magnum barrels heat up quite quickly which can result in a change in accuracy. In terms of ballistics, the 7mm magnum outclasses the 30-06 by a long stretch. Both cartidges are excellent and an opinion would be irrelevant. The choice is soley up to you as to what you need.
The .308 has a larger DIAMETER bullet, being 7.62 mm (versus 7mm) However, SOME 7mm cartridges may be longer than the .308, such as the 7mm Magnum.
26"
You will have to call Browning with the serial number.
Made in both Bolt and Semi-Auto versions