I have all the angles drawn at work so it'll be a couple days before I can get you an accurate number.
I tried the same thing as nobody makes a rail for a Sako L691 , I ended up just buying a blank rail from E.G.W. for about $20 and cutting it to fit my action , much easier and tons of time saved. I have since bought several more rails and have built a few differant bases for differant guns , its kinda nice to have a 20 moa rail for an Encore !!
yep the angles are 45 deg top and bottom. the gaps in my Seekins piccatinny rail are .205" wide and the raised rails are.187" wide
when I made my base for my Sako I tried several differant formulas and ended up using .0053" for drop per inch.
What I did was setup the rail in the vise on a riser so I could start the cut at the back of the rail and made that my start point. I then set up a dial indicator to read .0000" at this end , I ran the table over 7.250" and raised the rail .0384" on the dial , this equals out to .0053" drop per inch of rail , this worked out good for me , I haven't tested it yet but the few folks I've talked to that make bases say it should be real close to the 20 moa I was wanting.
I have since made a couple rails for some Encore shooters and they are all tickled pink