Getting ready to sight my DD in with 75 gr Tap. I have been shooting 55 gr. UMC. What should I expect the difference of point of impact to be at 50 yds., 100 yds. and 200 yds? Gun is 16" 1/7 twist.
Thanks
I’m afraid there are going to be other factors at play in POI shift besides just the ballistics of the round itself. The barrel harmonics and anything that affect it can result not just in vertical POI shifts but horizontal as well. The only way to know for sure how the different rounds will perform in your gun is to shoot them both and record the differences.
Sample of one, but the POA/POI shift for my gun was only about 2 MOA.
Colt 6920 with Knight’s RAS, supported, 100-300M, from a 50/250 zero with XM855.
Altitude 7500’, humidity ~20%, temps ~70F.
Shifting from Federal XM193 to 75 gr TAP T2 rounds moved group centers ~1 MOA horizontally (left) and ~1 MOA vertically (higher).
The group size at 100M went from about 2.5 MOA with XM193 to a bit under 1.5 MOA with TAP T2. The TAP group sizes are comparable with XM855.
Have seen similar effects in 1/9 barreled guns as well. Have always had both a horizontal and vertical component to the shift between lighter and heavier rounds.
Most likely in the 1-3 MOA area, though I have seen less and more, and can occur in any direction.
In short, you should be close enough at 100 to refine your zero without having to start at a closer distance.
Typos brought to you via Tapatalk and autocorrect.
Not 75gr TAP but a couple of points of reference:
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16" 6920 had BHA 5.56 Match (77 BTHP) 2moa rt of XM193 and 1.5moa rt of Green Tip. Negligible elevation change out to 200yds.
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16" S&W had 77gr less than .5moa rt of the 55 & 62gr loads and negligible elevation changes out to 200yds.
Keith