I PREFER to shoot 75 gr OTM simply because it’s more accurate and offers better terminal ballistics than 55 gr fodder. When I miss steel plates at 200 and 300 yards, I know it’s me and not the ammo.
But, I find myself shooting more 55 gr fodder because it’s easier on the wallet.
So the dilemma is: do I zero for my preferred load that I shoot 25% of the time, or should I zero for the cheap ammo that I shoot 75% of the time?
Zero for your self defense load.
You can also figure out the moa difference between zeros for each load and adjust every time, but that leaves too much room for error. If you do this I would suggest that you also learn each of the zeros from either the irons or scope adjusted all the way down and left. That way if you get confused while adjusting you can always return to this point and start again.
Again, I just simplify things and zero for my self defense round.
You zero for whatever you’re shooting at the time. You don’t want to be guessing when you lay your life on the line, so you should have your rifle zeroed in for the ammo you fight with. You fight like you train. If the rifle is zeroed for your fighting ammo and your training ammo has a different POI you’ll have to compensate for that. Do you really want to instinctively use the adjusted hold for the training ammo when you’re in a fight?
Go to the range and zero in with your fighting ammo. Record the sight setting. Zero with your training ammo. Record the difference in the sight setting. Reset the sights to your fighting ammo and shoot to verify. If hunters can record sight settings for the POI of different loads so can you
You’re more likely to introduce a failure point by switching dopes back and forth than you are zeroing with duty ammo and shooting trash for practice.
If you’re a precision shooter that does it all the time, that’s one thing, as the habit is ingrained, but even experienced shooters forget. Happens all the time, and we’re not talking about a hunting gun. Miss with a hunting gun because your POI is off as a result of having the wrong dope set is likely to be less hazardous than a miss while somebody is trying to make you assume room temp, unless the animals are suddenly arming themselves and I just missed it. I think that, mentally, you get more out of knowing how your holds may be different between your known-quantity zero ammo and the various stuff you might pick up for training.
Ideally, you zero and train with your known-good ammo, but nobody from the middle-class will fail to recognize that as potentially cost-prohibitive to many.
my home rifle is zero’d for 75gr tap but i shoot whatever is on sale running drills doesnt make much difference under 100m
This. My HD ammo and any of the crap I feed the gun under 100 yards shows a negligible difference.
I reload 55 gr FMJ-BT, 75 gr (PPU) and 77 gr (SMK)
I’ve experimented extensively with all 3 at the range with my HD/gaming gun (14.5" with T1), and found that with a zero established by the 55 gr, all types of bullets and loadings hover around the same area. I’ve shot steel plates (roughly the same size as a A4 sheet of paper) out to 400 yards using all three types of projectiles and all were able to make hits.
I’d establish a zero with your 75 gr rounds, and then see where your 55 gr hit on paper in relation to this zero… It shouldn’t be a big enough shift to matter.
Interestingly, different powder charges will move the zero in strange directions horizontally as well as vertically. I bet this has to do with barrel harmonics.
A better option might be to get another rifle or complete upper assembly.
I see considerable difference in 100 Yd POI with some M193 VS 75gr Tap and less with others. For example, 2009 IMI M193 prints about 2" higher than my 75 gr TAP at 100 Yds in my Noveske N4 (no big deal at close range), so you might try to standardize on something that shoots closer than what you have now. I also reload 75gr for a lot less than I can buy M193, but I have time to fart with reloading. You can get a reload to print very close to similar factory ammo, but it can be a pain to do so.
Why not keep book and write the zeros down for different loads like I do?