March 9, 2011, 06:56 AM
Hello all, been doing a general search, then decided to get right with it and put it to the pros!
I have a duplex crosshair reticle and want to know the ranging theories that apply, or what I can do to generate some ranging capability from it.
March 9, 2011, 12:44 PM
That depends on your particular brand of duplex crosshairs. It may take some experimentation, setting up 18" circles (to simulate deer-chest height) at various ranges and seeing whether the thick part of the horizontal wire is about right for a particular range, then the narrow part for another.
I don't think that works particularly well, preferring to use a ballistic calculator to find the best "point-blank range" (3"high or low) for a particular bullet/velocity out to wherever that takes me. If my memory serves me well, sighting-in my 130 grain .270 handloads at 2 1/4" high at 100 yards causes bullets to hit within 3" of the crosshairs out to about 320 yards.
Beyond that, holdover estimates are necessary, but not particularly accurate unless a laser rangefinder can be employed to determine the exact range.
March 9, 2011, 01:42 PM
not too difficult to use your 30-30 reticles as a range finder when I put a new scope on. I take a 16 X 32 piece of cardboard ( approx size of a shoulder to brisket, shoulder to tail on typical whitetails in my parts) and set it out at 100 yards on 4 power and see where it sits between the heavy and fine ponts of the reticles then out to 150, 200, 250 & 300 and see where the piece of carboard is relative to the reticles. Rule of thumb; dead on at 25, dead on at 250. Another one: say you know your muzzle velocity is 2800 FPS and are 3 inches high at 100. That should put you pretty close to dead on at 280 yards, 2500 FPS-250 yards, etc.