POI shift with powder lot change

[Kroberts]

How much of a POI shift is there normally when you change lot of powder? The other day a buddy and I were shooting at 1/2 gal jugs at 1000 yards and I was grouping right around the jugs. Which is about the normal grouping size that rifle does any more with its round count. At one point the poi shifted 2moa down and 4moa right and stayed. It took a few minutes to realize that was the point in my ammo box I had to open a new pound of powder. Wierd part was that I checked the 100 yard zero and the center of the group was to the right maybe 1/2" grouping in the 3/4" range, hard to tell on the steel since it left little craters that overlapped. I can understand the shift in the vertical but I don't understand the shift to the right at 1000 when the 100 yard wasn't near that much. Group size stayed the same just shifted. And the wind never changed. It went from ~0 windage to ~4moa. While my friend stayed with a 0 hold the entire time. The powder is H4350 in a 243win with the 95gr SMk. So is that a normal shift when switching to a different lot of powder?

Thanks
Kyle

 

[Barrelnut]

I just shifted to a new lot of H4350 and lost 130 FPS! Which is worse than your results. Never seen anything like that with Alliant powders...

 

[barefooter56]

How much of a POI shift is there normally when you change lot of powder? The other day a buddy and I were shooting at 1/2 gal jugs at 1000 yards and I was grouping right around the jugs. Which is about the normal grouping size that rifle does any more with its round count. At one point the poi shifted 2moa down and 4moa right and stayed. It took a few minutes to realize that was the point in my ammo box I had to open a new pound of powder. Wierd part was that I checked the 100 yard zero and the center of the group was to the right maybe 1/2" grouping in the 3/4" range, hard to tell on the steel since it left little craters that overlapped. I can understand the shift in the vertical but I don't understand the shift to the right at 1000 when the 100 yard wasn't near that much. Group size stayed the same just shifted. And the wind never changed. It went from ~0 windage to ~4moa. While my friend stayed with a 0 hold the entire time. The powder is H4350 in a 243win with the 95gr SMk. So is that a normal shift when switching to a different lot of powder?

Thanks
Kyle

Kroberts,
What looks small at 100 yards is HUGE at 1000 yards. Check the velocity of the load with the new lot of powder. I bet its slower which explains the elevation and the windage ( due to increased time of flight). Never assume lots are going to be the same or that powder loads will be the same as the powder ages. We have to test, confirm and keep an accurate reloading log book with good notations.

 

[Mikecr]

How do you see ~42" of horizontal while shooting at 1/2gal jugs?
Couple things;
Always retest, working upward, with ANY new load component.
Stop shooting at junk, and start using paper targets with precision aim points.
And you might want to get the gun shooting well up close -before moving further out.

 

[Kroberts]

Barrelnut, that seems like a big velocity shift. I didn't figure it would be that much.
I figured there would be a performance difference but didn't think it would effect the windage that much as opposed to the elevation. Especially when there was almost no wind with about 0-1minute hold to start with depending on if the breeze was present or not. The rifle performs about the same as it always has with this load except that I keep getting more fliers because the throat has corroded to a point that I can't contact the land with the longest bullet on hand seated in the case about .02 so that the bullet just stays in the case to even come close to the jump point the bullet likes. So right now I'm just making due until the new barrel comes in. ita not too hard to pick out where your group is at when your shooting at bare dirt, having a spotter, and you see the bullet going into a sub Moa clump bases off using the reticle and comparing the clump of impact to a known sized target, the jug. That's why I give the measurement in approximate Moa not an exact measurement since we don't know for certain. I want to shoot paper there to get a good indicator of what it's doing. But it takes about an hour round trip to set up a target of the ground is dry and we can drive around the field. So because of that my buddies and I like to shoot at stuff, usually a chunk of steel that is hanging out there so we just have to pull up and start shooting and make 1 trip to the target aight instead of two or more.I need to get ahold of my buddies chronograph and see how much shift there is. I'm not to concerned though, we just shoot for fun so if I can get close enough to be able to see a miss im happy since then I can just pull it in and have fun either hitting the steel or grouping around little jugs and clay pigeons. But once I get ahold of the chrono I'm going to sit down and see what's going on and make sure the rifle is where it should be. on this go we just planned to go shoot that day and I needed something to play with so just loaded up with the new pound of powder and went. And noticed the, to me, massive shift in windage

Sorry that's a little long winded with random details. I just like to explain all the little details so you know what's going on.

Thanks for the comments and suggestions,
Kyle