vertical dispersion

[Luckus]

Other than poor shooting, what causes shots to go high? I shot a makeup match yesterday at 300 yards F class with my new 6 Dasher. First two everyting was nice and round. We shoot 15 shots for record and I had 148 4X and 148 6X. Target 3 145 4x, but five high in the 9 ring. It was probably driver error but I wonder what else it could be. Barrel was warm but not to hot to hold. 33gr RL15, 105 Amax and ccI450, 2979 mv.

[memilanuk]

Lots of things...

Shooter Error:

Shoulder pressure
Cheek pressure
Rear bag settling
Stock catching on something - rear bag, front bipod, sling stud, etc.


Reloading Error:

Inconsistent powder charge
Inconsistent priming
Inconsistent neck tension


Environmental influences:

Wind direction*
Terrain features**
Mirage***


* By itself, wind direction may or may not show an appreciable amount of influence on vertical impact - some swear by it, some at it.
** Terrain features tend to magnify the effect of wind direction - in effect, 'funneling' or concentrating the wind in a manner that may push the shots up or down.
*** This one can be both environmental (mirage increasing as the day warms up, heating the ground) and shooter error, from not using a mirage band, especially on warm/hot days with little to no breeze, allowing barrel mirage to adversely effect your sight picture.

There's probably any number of other factors, but those are the ones that come to mind right now...

[82boy]

As mentioned it can be a whole buch of things.
Barrel heat will affect a bullets impact, could also be that the scope was hot. (When sitting under the sun between shooting rounds/relays cover the rifle with a towel.) could also be mirage off of the barrel, that is why it is a good idea to have a mirage shild.
Could have been a light change, when you shot the first was it could have been sunny then changed to cloudy, or the sun could have been behind a large cloud. (Lights up, sights up.)
Could be that the load as too hot, as temps rise throught out the day, you may need to back down your load.(This is why benchrest shooters like culver powder measures they will back it down a click or two as the day goes on.)
Could be a stronger headwind making the bullet rise more.
Could be diferent mirrage patterns, you was shooting a right to left or vise versa, then shot a boil.
Then there is shooters error.

[Luckus]

Thanks for the replies. I think I could improve my technique as far as shouler pressure and getting comfortable on the rear bag. I fight the rear bag all the time. I should get a taller one. Also the light condition did change the last target. I was in the shade all the time but the target was shaded sometimes and in the sun at other times, most of the time it was partially shadowed, like the sun on the edge of a cloud. Luckus

[lal357]

my rear bag was to low also one thing that i did was to take a piece of 2x6 wood and uaed some spray gun to glue it to ti been working great for over a year now .all of the above can be the problem for me with an old barrel i had if it was hot outside and i shot really fast it would go high and to the right to the 9 ring . i started checking my barrel as i shoot and got a timer to look at to keep my time slower(my fastest time was 20 rnds in just under 7 min) i try to finish as close to the 20 min time limit we have as possible.the mirage shield is very handy to use it deflect the barrel heat away from my scope view.

[Luckus]

I put my T36 Weaver on for the rest of the year. I was using a 6.5x20 Leupold before. This morning I was testing a couple of different loads with H4895 and the 105 Amax. It was faster but not any more accurate. So I used my standard load 0f 33 gr RL15 to get a 600 yard zero. I fired the first shot on the wrong sticker, which was low,(i forgot this scope has 1/8 clicks) I cranked it up to where it should be. I had put a black dot 11.7 inches above POA pulled the trigger and the dot had a hole in it. The next three followed suit. 4 in .265 and three in .106. All five rounds chronoed at 3030 each. SD=0 ES=0. Somedays things just fall together. Now if I could just win a match. Luckus

[Luckus]

I did win the 1000 yard match his year with our small group. We shoot four each at 300, 500 and 1K, throw out the low score and agg the rest. I lost the 300 by 2, the 600 by 8 and won the 1k by 1. Even a blind dog finds a bone once in a while. Luckus

[Broncman]

My last ftr match I ran out of the BR4 primers. My vertical sucked at 600. Everything else the same. Scrounged through my stuff and foumd some loads I had forgotten about that had the BR4 and used those for the last match of the day and vertical was great. I have missed called some tail winds that caused a sudden elevation change.

Neck tension also causes it. When my vertical starts spreading out I know it is time to anneal.