What Causes Horizontal Dispersion When Testing Loads

[Tyler4565]

When testing loads,assuming the proper equipment(aside from wind flags) and shooting technique are present, will the only thing that causes horizontal dispersion in a group/ladder test be the wind, or will different loads impact the target in a different place(windage wise) just because they are loaded differently? I am trying to decide whether to ignore left and right dispersion when testing loads and just pay attention to vertical dispersion or not.
Thanks in advance.
Nice to have a place to learn from the experienced guys

 

[Dusty Stevens]

A string horizontally is usually the wind. It can cause vertical too so any testing must be done over flags

 

[BradY]

Wind, mirage, technique and load tune itself. Beware some loads shoot flat vertical but seem to be more wind affected than loads that have a tiny bit of vertical in them. Get a read of Tony Boyers book if you can.

 

[potatoe]

Even without flags, if my groups are always horizontal I'm changing my load. If possible it is best to shoot with flags (any type even bright tape is better than nothing) but because a bullet goes left or right doesn't mean that it's always the wind. What distance are you doing your ladder test?

 

[LHSmith]

First off, without testing with flags - "you're just plinking" (Stole that phrase from a member here and it says it all). However, when one becomes adept at reading "conditions" he can try tuning out some horizontal by adjusting neck tension and seat depth. Take good notes listing temp./humidity while testing as accuracy will be dependent on test conditions...despite what powder companies tell you.

 

[Tyler4565]

Potatoe, I did the ladder test at 300 yards and selected my load based on it. I'm scratching my head a bit because the load I picked from the ladder test made two three shot groups that were barely under an inch at 300, but then I went out again to confirm the load this morning, and the same load shot about six inches wide, with about 1 inch of the spread vertically, the rest was windage. It was just a little windy, but not enough to cause 2moa

 

[Tyler4565]

Do you guys just watch the flags and try to shoot when the flags aren't moving?

 

[LHSmith]

Well you could, but actually your best results will be with some mild constant push, head, tail, true left crosswind, or true right cw. Quartering winds are not the best, but the main thing when learning to read conditions is to shoot when the flags are doing the same thing at each shot....and be mindful of intermittent sun/shade intervals when shooting a group. The #1 tenet (principle) in Benchrest is " do everything the same from shot to shot as much as possible", which includes bench technique, ammo as duplicate as possible, as well as shooting in as close to the same conditions as possible.
Edit to clarify that in shooting a crosswind the angle of the tails (ribbons) is much more critical than a head or tail wind. It helps if you visualize and read the angle of the tails like positions on a clock dial. .....no wind = 6:00 (tail hangs still), strong wind from left = 3:00 (tail extends straight out) etc. You will be best served with tails @ 4 -5 or 7-8 o'clock conditions IF constant or repeatable (wind usually cycles and repeats a pattern every few minutes).....and don't keep a round in the chamber while waiting - Remember "everything the same"- incl. ammo temp.

 

[potatoe]

LHSmith is putting out great advice. Duplicating loads and shot strings isn't as easy as some think. Also what was your horizontal during the ladder test?

If possible get at least some surveyors tape and dowels for at least some indication ( i know actual flags are very expensive) in the morning the winds are normally calm enough to get some shooting in. What was the temp change between the two days? Sometimes a colder day can influence the rifle more than I want it to. This time of the year can be a little tricky. Plus I've heard from a reputable shooter/gunsmith (I've never tested or researched this so just take it at face value) but colder air wind pushes will influence wind deviation more so than warmer air because he said the colder air more "condensed" than warmer air. Again I dunno, but I have a BR that should be done in about a week or so and I'll try out his theory.

 

[LHSmith]

It was just a little windy, but not enough to cause 2moa

How does one make this assessment with no means to monitor the true value of the wind? Without flags you are just guessing .......wasting components, barrel life and time.

 

[Tyler4565]

Potatoe thanks for the surveyors tape idea. Actual wind flags are quite expensive. The horizontal during the ladder test was less than less than three inches. The weather was consistent both days. LHSmith, I made that assessment using the vortex ballistic program. It said a 10 mph wind from 3 oclock would blow the bullet 2.5moa at 300 yards. LH, so basically, when you go test loads, you just make sure your flags are indicating the same thing from shot to shot? What do you do after you find a load that groups well, try the same load on another day and see if it does just as well? It sounds like you don't expect a load to perform consistently from day to day.

 

[Tyler4565]

In other words, is it not realistic to expect to find a given load that will shoot really well in a wide range of conditions? say 1/3-1/2 moa

 

[DanSavage]

What cartridge are you shooting?

 

[Tyler4565]

Currently loading 308. Norma brass with Sierra 168 HPBT with 44 grains of varget. BR2 primers

 

[LHSmith]

Potatoe thanks for the surveyors tape idea. Actual wind flags are quite expensive. The horizontal during the ladder test was less than less than three inches. The weather was consistent both days. LHSmith, I made that assessment using the vortex ballistic program. It said a 10 mph wind from 3 oclock would blow the bullet 2.5moa at 300 yards. LH, so basically, when you go test loads, you just make sure your flags are indicating the same thing from shot to shot? What do you do after you find a load that groups well, try the same load on another day and see if it does just as well? It sounds like you don't expect a load to perform consistently from day to day.

What I meant was you had no way to verify the wind value.
When I find a load that shoots well (as determined by several 3 shot groups for a hunting rifle or several 5 shot groups for a target or varmint rifle, I test on another day with relatively same conditions, then test in hard left and hard right conditions to see how wide the tune window is. If the accuracy falls in either condition, I know which condition to avoid shooting in in order to maintain my accuracy goals.Many times a barrel /load combination will favor a certain crosswind direction ( L or R) and be troublesome in another. I could also continue load testing looking for a tune that shoots equally well in both wind directions, but in certain chamberings you have to take barrel life into consideration.
In shortrange Benchrest we generally don't expect a load to perform consistently from match to match ( i.e -from one hour to the next) but we are measuring our success out to 4 decimal places...and we have to maintain this level of accuracy "all day long".

 

[LHSmith]

In other words, is it not realistic to expect to find a given load that will shoot really well in a wide range of conditions? say 1/3-1/2 moa

Sure...if you are blessed with an above average barrel. If your barrel is mediocre, you can test till the bore is smooth and never meet your criteria.

 

[Homerange]

When testing loads,assuming the proper equipment(aside from wind flags) and shooting technique are present, will the only thing that causes horizontal dispersion in a group/ladder test be the wind, or will different loads impact the target in a different place(windage wise) just because they are loaded differently? I am trying to decide whether to ignore left and right dispersion when testing loads and just pay attention to vertical dispersion or not.
Thanks in advance.
Nice to have a place to learn from the experienced guys

Never assume.
Acquired a cheap 7.08 sporter a while back and while shooting in a scope it was horizontal stringing 2" @ 100yds.
But less than 1/2" vertically.

Google searched horizontal stringing........LOOSE action screws.
Now it cloverleafs. 8)

 

[M14AMU]

Parkinson's disease and wind!

 

[Mozella]

;...............snip.......... Without flags you are just guessing ......snip.........

I would argue that WITH flags you're still guessing. Otherwise they would call my sport "F-Class X Ring Demonstration" rather than F-Class Competition.

 

[LHSmith]

;...............snip.......... Without flags you are just guessing ......snip.........

I would argue that WITH flags you're still guessing. Otherwise they would call my sport "F-Class X Ring Demonstration" rather than F-Class Competition.

Reading flags beyond 300 yards would be problematic for obvious reasons. All successful short range BR competitors in the last 35 years have used flags. SR BR = 100 - 300 yds, F-Class 300 - 1200 yds.