The first step would be to make sure it is on an SB2 frame and the FAQ's tell you how to do that, and if you aren't sure just call the number Tim furnished and they will confirm it.
Barrels can be interchanged and as long as you have an SB2 frame for a high pressure barrel, and the barrel fits snug and locks up tight, then there isn't a problem at all.
If possible, you could always ask the aquaintance if he bought the rifle new or was it used?