Prep method
That prep could be used to do what you want. Once you get as close an estimate as you can with JBM on the MOA drop. 40 MOA is going to be in the ball park to begin-with. I have no expensive tools so I improvised when I began attempts at 1,000. I use a good Leupold 6.5-20 scope but it has a 1" tube. So I needed an elevated base. I picked a Leupold 20 MOA 1-piece base and when I screwed the front down to the receiver I could still get a dime between the rear of the base and the receiver. Needless to say, I got no elevation increase at the 1000yd range. Then I tried another manufacturer's 20MOA base and having found mechanical zero of the scope (that's where the crosshairs are level with the body of the tube), fired the gun at 100 yards and came-up 12 inches high when I was expecting 20 inches high - that's only 60%. So I sent that one back (and the mfr told me that was the first time he'd had a return in 20 years of his business operation). He finally conceeded it was the reciever finish to base fit that must be off. Tried a third base, 30MOA made by Ken Farrell, fired the gun at 100, came up 29 inches high and have stuck with that to this day. So, if the method of shoot-high testing at 100 is applied to getting on target at 1,000 then certainly it can be used.
That prep could be used to do what you want. Once you get as close an estimate as you can with JBM on the MOA drop. 40 MOA is going to be in the ball park to begin-with. I have no expensive tools so I improvised when I began attempts at 1,000. I use a good Leupold 6.5-20 scope but it has a 1" tube. So I needed an elevated base. I picked a Leupold 20 MOA 1-piece base and when I screwed the front down to the receiver I could still get a dime between the rear of the base and the receiver. Needless to say, I got no elevation increase at the 1000yd range. Then I tried another manufacturer's 20MOA base and having found mechanical zero of the scope (that's where the crosshairs are level with the body of the tube), fired the gun at 100 yards and came-up 12 inches high when I was expecting 20 inches high - that's only 60%. So I sent that one back (and the mfr told me that was the first time he'd had a return in 20 years of his business operation). He finally conceeded it was the reciever finish to base fit that must be off. Tried a third base, 30MOA made by Ken Farrell, fired the gun at 100, came up 29 inches high and have stuck with that to this day. So, if the method of shoot-high testing at 100 is applied to getting on target at 1,000 then certainly it can be used.
