Yes, no, maybe, and eventually...
I'd go out on a limb and say chances are that '
yes' chances are good it will fit.
However, you might consider this: if you bought the gun used, it is possible somebody put a 280 barrel on a receiver that doesn't qualify for high pressure barrels offered by the accessory program. (It has been known to happen.)
If that is the case the factory will not fit a 243 to your receiver (a 243 being one of the high pressure barrels - which are marked with * on the barrel accessory page of the factory website). This would fall under the
'no' category.
A list of serial number letter prefixes in the faqs tell you what year your receiver was manufactured, and if it was 1999 or later it qualifies for the * marked barrels and the factory will fit one in 243. This is the definitive answer
yes. The best way to find out for sure is to telephone them with the serial number, they will tell you. Website and toll free number are in the faqs.
On the other hand, if you buy a used 243 barrel it may or may not fit, which is where
maybe comes in - but there are ways (again in the faqs) that explain how others have fitted barrels, and we arrive at
eventually because some tinkering and fitting time will be required.
So you see there are many possibilites, you just need a bit more information to determine the final answer.
I also second the motion proposed by stalking bear that you consider reloading if you plan to shoot a lot. Ammo for 243 can add up too.
Have fun.
