450,
Great minds must think alike, my 450 NE is currently getting the barrel screwed into it, mine started out life as a 375 H&H. Building mine for the same reason as you.
Might meet you at the Nationals in July maybe?
Just got the barrel for mine in from the U.S last week, went for a Pac-Nor 3 groove 14 twist, they chambered the barrel over there for me, finished length is 28", can't wait to get it in a few weeks to see how it shoots.
One other tip, I'm having my gunsmith mill another dovetail in the quarter rib, to put another Ruger rear sight in the groove, sort of like a cheaper version of folding leaf sights, the close one for 25 and 50, the other one for 100.
Saves having to hold low in the rapidfire events.
450 A.M