Vertical stringing with increase in charge weight should go up right?

[Sticks]

My last load development run shooting a 20" Howa heavy barrel, no muzzle device, prone off bipod and rear bag resulted in every 2-3 charge weight increases I had to dial up (READ - shooting at 100, had to dial for 200) on my scope or would end up seriously off target (3/4" dots placed on a 3" grid).

This happened with 3 different bullets, and 4 different powders.

Everything still tight, and going back to known ammo and POI I had to return to zero.

Anybody else encounter this? We are talking about over 2 mil in correction over a 3 grain increase in .3 steps.

[imaguy3]

I've encountered sometimes significant poi change(several inches at 100 yards) with different brands of ammo within the same weight, so I assume that would be a similar scenario. I just chalked it up to different barrel harmonics throughout the firing cycle due to charge weight and type of powder they used.

However I'm assuming you're using a bolt gun? Even though it doesn't sound like your issue, I have experienced large vertical shifts before using a bipod on two different rifles. One was a Marlin bolt gun that had a flimsy plastic stock. Resting the stock on sandbags would be dead on at 200. Put on a bipod and "load" it properly and all of a sudden I was 12" high. It was causing all kinds of flex and contact which drastically changed my poi. The other was a buddies AR that had a pic. rail attached to the bottom of the gas block. Same thing happened with that gun b/c obviously it was pulling on the barrel...

[LR1955]

My last load development run shooting a 20" Howa heavy barrel, no muzzle device, prone off bipod and rear bag resulted in every 2-3 charge weight increases I had to dial up (READ - shooting at 100, had to dial for 200) on my scope or would end up seriously off target (3/4" dots placed on a 3" grid).

This happened with 3 different bullets, and 4 different powders.

Everything still tight, and going back to known ammo and POI I had to return to zero.

Anybody else encounter this? We are talking about over 2 mil in correction over a 3 grain increase in .3 steps.

Something isn't calculating out properly here.

You said your elevation changes equal said changes between 100 and 200 yards which equals about a minute or maybe 1 1/2 minutes max. Yet you say your elevation changes are 2 mils which is 6 1/2 minutes.

Wouldn't be surprised to see a minute or two change in elevation given a 3 grain change in powder with a Grendel. Would be surprised it it were 2 mils (6 1/2 minutes).

LR55

[Sticks]

The shooting 100, dialing for 200 was an example. My groups kept dropping, then I would dial until my reticle was at POI then continue.

Actual mils dialed, looks to be .8 going off the target for about 6" of total elevation correction from 2469 fps to 2718 fps with a 130 ELD. I was going off memory from a May or June outing ....

Anyhow....

Howa bolt action in a MDT chassis. Zero contact with the barrel under extreme bipod load.

Still perplexed as to the lower POI with higher velocities. I was doing some more research and the "Your impacts should string low left to high right in most barrels" got me to thinking about it again.

[Jakal]

Sounds like the BC is working for you in this case, the faster it goes, the flatter it goes. Since you haven't hit the apex of your trajectory, the bullet is still rising on its flight path. Or looks like it is hitting low. Try the same load at 300 and see where it hits.

I was always told if you get vertical stringing on a ladder, the powder isn't right. Either not enough, too much or wrong powder selection. Once you get close to a node, the stringing should come in, unless it is a powder selection issue. Would need to change powders at that point.

Plays into barrel harmonics.

That is from a wise old man who has been reloading for 60+ years (my dad)!

[grayfox]

POI shift does not necessarily shift up with faster MV's, although many times it does so; it depends on barrel angle (harmonics) at bullet exit. Since we are talking about 100+ yds compared to the muzzle tip, 0.001's of inch angle shift translate into inches at the 100 or farther yds distance.