Odd horizontal stringing during load development

[fat_46]

Working up some loads for my 22-250AI the other day I noticed one of the loads stringing horizontally. I had fireformed with 36gr of H4895 behind Nosler 50gr BTs with CCI BR2, so that's the load I started with. Increasing .5 gr, and firing 5 per powder weight everything seemed to be going great, with accurracy increasing as powder increased. 38 and 38.5 grains both shot one ragged hole. However, when I got to 39 the group opened up very substantally. All rounds were on the same plane, and touching each other, but they carved a horizontal line!

I know the most common causes of horizontal stringing are caused by TIBTT,the idiot behind the trigger), but I don't think that was the issue here. Any ideas? I'd really like to get past 39 grains of powder.

Thanks in advance.

Pat

 

[taxman]

Casual observance...

If the rifle is shooting one hole groups, why are you chasing a heavier charge?

I used to get caught up in all the number games as well. Always looking for xxx grains or xxx velocity. Now, I am very happy when I get one hole. Stick with that load and shoot a few groups.

It does not count if the second shot is faster than the speed of light if you cannot hit what you are aiming at!

Have fun.

Did you have wind flags or indicators up? I have learned with a 222 Rem groups get smaller with at least surveyors ribbon up. Good conditions can be very misleading when you cannot see the wind.

 

[fat_46]

Don't get me wrong - I'm very, very happy with the accuracy. I'm just looking for the proverbial laser beam for prairie dogs!

 

[taxman]

I am not trying to beat ya up.

I have a 243 AI that just won't put up the numbers it is "supposed" to. It will do the same horizontal stringing as yours does when I try to push velocities. I backed off and settled with the small group instead of speed.

Try a different powder or primer combo.

Do you have a chronograph? Are all case dimensions ok? Any pressure signs?

On a lighter side, the dog won't care how fast that bullet hits him or misses him

 

[fat_46]

No worries! I try to never bring the chrono when inital load testing - just one of those shooter superstitions I have,like never buy ammo at the same time as buying a new gun... don't ask, the people in the white coats are helping me with it!)

Absolutely zero pressure signs, and brass growth was almost immeasurable. One split neck out of 35 rounds, but that was on the lowest charge, so I'm chalking it up to a brass issue.

Rough guestimates on velocity still have me in a very good "red mist zone". My query was more of a "what happened/what caused it" than anything else.