Originally Posted by
JSantoro
With the TA31F, you're ballistically closer to a 100m zero if you do it at 33m (36 yards). 25m will still work, but expect to print fairly low @ 100m.
Phase I: POA/POI @ 33m or 36yd, using the 300m aimpoint, per the diagram above. 9clicks/inch.
This is a field-expedient method, designed to ensure you are on paper @ 100m. You still need to do a 100m *METERS, NOT YARDS!* zero to be balls-on @ 100m. Going from 33m to 100m, the trend is for your group to be 1/2"to 2" low. If you insist on measuring in yards, make it 109 yards (which = 100m). The 27' of difference between a 100yd (incorrect for the BDC) and 100m (correct for the BDC) zero will make or break you with shots beyond 300m.
Phase II: POA/POI @ 100m, using the tip of the chevron to confirm/fine tune. 3 clicks/inch.
In between ANY and ALL adjustments, don't forget to replace the caps on the adjusters and give the windage adjuster a solid thump with the heel of your hand. This ensures that the prism is set in both axes of movement. If you don't, your next shot will certainly follow whatever adjustment you did, but the next ones may not because the prism may move under the recoil impulse.
Phase III: PROFIT!!
EDIT: Your optic height-over-bore is 3.755" with your LOS crossover being 33m. You can chart stuff like that on a ballistic calculator, or use the 300m aimpoint as a good place to start, but you will have to figure out the specifics for yourself. Generally, though, the idea is "red you're dead," i.e., from 0-300m, get the chevron on the center of the visible mass of your target, apply what fundamentals you can given your situation and press rounds until you get to Phase III or can judge your impacts and adjust enough to get you to Phase III.
Of course, if you have a green or amber reticle, the idea is the same but the ditty loses cuteness because it doesn't rhyme.
