I've shot many AR's that were spot on with every shot. I've had some that had first round POI shift, and some with a POI shift on bolt round lock back. The last round, bolt back, lock open is a common POI shift with some AR's. If shooting a 5 shot group, I will load up 6 rounds in the mag. the first round loaded is my dedicated last round for chambering. It gets beat up. But I'll load that dedicated round first, then my 5 rounds to shoot for group. I don't want that fifth round to lock the bolt open and have a POI shift. I'm trying to eliminate variables that cause POI shifts that can effect the POI of that round, and open up the group.

I've talked to some shooters where they will want to shoot a 3 shot group out of an AR. They load up 3 rounds in a mag, and shoot 3 rounds, and the bolt lock back on the third shot. If your AR has a slight POI shift on the first round, and the second round goes where it's supposed to, and the third round causes a POI shift, you will not be getting a tight group. You need to know if that first round causes a POI shift of not. And I'll eliminate that first round out of the group, if I see this, or include it with a notation. When testing for groups, I NEVER let the last round lock the bolt back. I contribute this to the change in recoil impulse. Also, when shooting an AR, you have to "drive" the rifle more and have better fundamentals.

Out off all the atmospheric conditions, temperature, altitude, barometric pressure, humidity's roll is a non-variable. Having big humidity changes isn't going to move the needle of the ballistic performance of a rifle in any measurable way. What minute changes it may have are lost in the other atmospheric changes, spin drift and wind drift. You just can't measure or correct for it.

So try it.

Try what? One thing I really understand is ballistics and ballistic programs. I've assisted on a few of the top ballistic programs that are out there. If you're chasing humidity as a root cause of POI, that's like trying to rope the wind. There are far too many other variables in play to say it's humidity. It truly is a non-factor. Reach out to Brad Mallard at JBM or Bryan Litz at Applied Ballistics. These are two of the top minds in ballistics. They'll both tell you it's just not a measurable data point that you can correct for.

I’m not referring to shot to shot humidity. I’m talking about moisture in your barrel that is there on the first shot and will remain dry on subsequent shots. It can actually be extreme in some cases if you bring your rifle out of a cooler environment than your shooting in.

My apologies, I miss understood where you were going with this. Yep, depending on the gun, temperature differentials between inside and outside it could change POA/POI.

My apologies, I miss understood where you were going with this. Yep, depending on the gun, temperature differentials between inside and outside it could change POA/POI.