The significance of vertical or horizonatal grouping with load development

[Boomer79]

I had an experienced shooter tell me that as you develop a load a vertical grouping spread means the amount of powder needs to be adjusted or a change of powder. If it is a horizontal grouping spread the bullet seating depth needs to be adjusted.

 

[Terry]

The vertical part can be right. Usually adding more powder brings the groups in. However vertical can be caused by many other factors.

Terry

 

[artbosco]

I had an experienced shooter tell me that as you develop a load a vertical grouping spread means the amount of powder needs to be adjusted or a change of powder. If it is a horizontal grouping spread the bullet seating depth needs to be adjusted.

All things being equal, vertical can usually be reduced by a powder adjustment within .6 [6/10] of a grain range, and with neck tension and seating depth adjustment used for fine tuning.

Once bullets are going through the same hole, it's been my experience that horizontal spread is shooter induced, that is, caused by pulling the trigger at the wrong time, for example, in a wind letup or a push. Shoot over wind flags for confirmation.

 

[necchi]

Wives tails (kinda). Unless he was just speaking off hand for a conversational point.
Given that the rifle has no bedding or stock issues;

*Some what/mostly correct with the vertical. Heating issues can cause vertical in some guns.

*When I see Horizontal and it's not the wind,, It's me! One must remember the biggest variable is the shooter himself, if you can be honest with yourself you can learn and improve.

Bedding issues affect both. And proper bedding and/or stress relief must be addressed if you want the most out of the rifle. Helping the barrel and receiver fit the stock properly isn't all that hard, and even minor adjustments can help alot ( a different topic)

 

[Keith Glasscock]

Yes, indeed, horizontal is almost always me (too many rifles agree). I can throw a shot 3/4 MOA by moving my head at the moment of ignition (did it yesterday - darn, it was a .2) I can also do it by not getting my finger exactly square on the trigger - I drive the muzzle with my trigger finger!

Depending on the rifle, trigger, bench setup, etc. The shooter becomes ever more important to controlling horizontal. We all say that you can't buy your way into the winner's circle, but the rifle can help you limit the shooter imposed variables.

As for me - more trigger time!

 

[in2deep]

My 6BR proved to me beyond a shadow of a doubt that seating depth can cause extreme horizontal. I never would have believed it if I didn't see it personally...woulda bet a c-note against it.

Began test with Sierra bullets jammed about .025 with various laddered loads and had extremely erratic shots with crazy horizontal with some shots actually 8 inches on either side of the bull at 300 yards.... it was a real horror show.... rifle/scope was brand new never fired so anything could happen. Thought for sure the scope was broken or had a dead cow in the barrel till somebody gave me 5 rounds of factory Lapua ammo to try out and they miraculously held one bullet hole of horizontal with all holes about touching vertically at 300 yards.

I measured one and determined they were all jumping so next time out tried the same test jumped .020 and the gun repeatedly shot little bitty groups at the same distance.

No lie it was really bizarre and had me seriously thinking about taking up golf for for a few minutes. Shortly after I heard a famous PPC benchrest shooter explain that he could actually 'feel' when his rifle was out of tune and indeed the gun recoiled strangely shooting the very-out-of-tune ammo.

 

[butchlambert]

Tune and seating depth can affect horizontal. Other than gravity, what is different from tuning vertical or horizontal? A barrel doesn't know vertical or horizontal.
If you ever install a tuner on a barrel, you will see how it can affect every axis. You can make the bullet print several different ways fooling with the adjustment.