Yes the locking lug can be ground down on the rem barrel to fit the receiver with a dremel tool.
Remington 700 .243 twist rate is: 1 in 10" you can google it like I did.
1 in 12"
100-400 USD
Only Remington knows.
was it made in the custom shop at Remington firearms has heavy barrel and Monte Carlo stock
3 letter code stamped on left side of barrel. Check Remington Collector's Assoc for key to date codes.
Best left to a factory trained gunsmith.
Remington Model 700 bolt action rifles in 7mm Rem. mag. have a 1 in 9 right hand twist (one full turn in nine inches of barrel). This will accomodate bullet weight/length up to 175 grains.
100-425 USD
No because the barrel is made for that specific caliber and will not wear out the barrel.
Depends n which version of the 700 and condition. Around $500-$750