I've got the serial number narrowed down but it just easiest to think in terms of the forward angle changing at the beginning of 1984 and you will be very close.
Because the serial numbers aren't assembled in order it is real hard to pin point an actual serial number for the change. BUT 1984 works pretty well. The forearms before and after the change an be changed to fit the earlier or later rifle but they do take some changes. It's easier to fit an early forearm to the later action, That's just a matter of removing wood Going the other way is a bit more difficult and for proper fit requires some fill at the rear of the forearm to get it to fit the receiver properly.
Yes, you could use the RSI wood on your riffle with the appropriate changes. I don't think there is enough wood to open up the RSI forearm to fit a "B" barrel'. If it is possible, it will require quite a bit of work on the factory metal tip for the forearm. You could of course have the "B" 7mm Mag barrel turned down to "A" profile and and cut to length.
As mentioned sights migtt be an issue but you can order them from the factory. An "A" rib with the dovetail for the rear sight will cost you $78. The rear sight complete with all the screws, washer, blade etc will run you just over $40. Plus shipping. You can order the "A" sized front sight and the spring, plunger and blade for $73 or so. Be sure that you get the holes for the rib drilled in the correct place.
The front sight as purchased from the factory is NOT a perfect fit for diameter AND taper. You can do the work yourself but it's a pain in the bum to get it opened up enough with the right taper. I used the last 6" off a "A" barrel that I thinned down just enough that it's the correct diameter when wrapped in crocus cloth. Then use it to open up the sight. Go slow and trial fit often.
The final question would be, why in the world would you want a 7mm Mag with THAT short of barrel??? Won't do anything the 7x57 won't do if you go factory length. Be a LOT easier to sell the 7mm Mag and start loking for a RSI 7x57, IMHO. ;-)
On of the worst selling #1s of all time? The 7mm Mag non prefix AB and that barrel was longer than the RSI barrel. ;-)
Just took a quick look and the RSI came out in the catalog in 1984. It would be a fair assumption that the forearm won't fit an earlier action, without modification.
Good Luck
Ross
