I don't believe a .3 difference is going to effect anything noticable. I don't know if the onwer of that rifle bought one before Remington changed it, I don't even know if Remington has changed the specs for the barrel. But what do I know?
it depends, this could be one of the limited production "mil-spec" 700P's. If it is, it does indeed have the same barrel as the M24's. The problem is that its all a gimic. remington had a number of M24 barrels that did not meet specification for M24's, but they were still good usable barrels. So they mounted them on 700p's and sold them as "mil-spec". To be honest, they really don't shoot any better then the standard 700p's, they just cost a lot more.
I don't know the price difference, but I do know the quality difference.
The rem 700 PS is a factory made rifle. Remington "gang taps" their actions. Not real good for keeping tight machining spec's. If the bbl threads are not square, the barrel will not go on square. The trick is to make one dead on line from the back of the striker in the bolt, to the muzzle of the barrel. this would inclued the bot body and the lugs of the bolt, as well as the face of the bolt. If a skilled machinest puts the barrel on this kind of accurized action, it will be that way and you will have a very accurate rifle. Put an out of spec barrel on a production made action, and you will not have anything better than a standard rack grade hunting rifle. It won't matter what kind of stock they put it in or what kind of RAZZOO finish they put on it, you won't have what you are looking and PAYING for. A really good quality long range rifle has to be made to YOUR spec's, not some one else's. And be made buy some one that knows how to do it! As I hope you can see, there is a big difference. I hope this answers part of your question. Thanks for your time.