Dead on at 100yds 4inches right at 400yds

Once again. You are perfect vertically. Your first group was 3 shots one inch right of center(maybe .75 right), and the second group is about 3.3 in. right of center, again perfect vertically. That's just a light breeze that came up between the first and second group, that you didn't know about. It really is the wind. I've seen it happen at ranges from 300 to 800 yards, and sometimes its so light that if you or your spotter aren't paying close attention, you won't know it has happened. And there's always wind. There's just no such thing as a perfectly still day. If you went out tomorrow and the wind was 3 mph right to left at 400yards, you'd be 3 inches left with the center of the group. If you were doing anything wrong in your shooting technique you wouldn't be shooting .5 moa at 400 yards. Also, spin drift would only account for about .7 or less inches at 400 yards. Its sufficiently minimal that it doesn't get calculated in for snipers in the military until shots are past the 700 meter range or farther, depending on barrel twist. Almost all other factors such as altitude, humidity, temperature etc. effect vertical placement and not horizontal impact. Someone here mentioned Coreolis force, which is earth rotation during flight time of the bullet. You might get 0.2 inches at 400 yards, which your group would mask. It isn't worth worrying about. I shoot with retired snipers, and am a retired advanced marksmanship instructor for the Army, and this is just caused by a slight wind. By the way, no deer, antelope or elk would notice that your shot placement was 2 to 3 inches right of point of aim. All your shots are going to hit vitals and kill your animal. Also, remember: perfect is the mortal enemy of good enough. You'll chase perfect forever and never see it.
 
There is never "no wind". Keep that in mind. There may not be enough wind for you to miss the vitals of the animal but somewhere along the way, there will be wind. At least in my experience.

A 4-5 mph wind from left to right would push you off that far and if you were off a little bit when you shot then even less wind can make you off mark that far.
 
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Buzzyb's second target shows as tilted right compared to the first target. If it was tilted and he tilted his rifle/scope to align crosshairs to target, then he would induct the type and magnitude of error he got. Seems to me a likely case of a loose nut behind the (rifle) butt!

He set his scope is level….really? Truly level would be parallel to the horizon line on a flat, smooth lake or ocean. I.E. the vertical line would be true straight up. Tilt to the right and see POI shift to the right with all else staying the same.

Jim Irwin
 
Buzzyb's second target shows as tilted right compared to the first target. If it was tilted and he tilted his rifle/scope to align crosshairs to target, then he would induct the type and magnitude of error he got. Seems to me a likely case of a loose nut behind the (rifle) butt!

He set his scope is level….really? Truly level would be parallel to the horizon line on a flat, smooth lake or ocean. I.E. the vertical line would be true straight up. Tilt to the right and see POI shift to the right with all else staying the same.

Jim Irwin
If you will look carefully, you'll see that both targets are no longer on a board. They're sitting on a table, and the second target is laying on top on another target sheet (possibly the first one). He removed the targets from the backboard to take pictures of them, I'm sure. But Buzzyb can clarify that himself.
 
how about this one: assuming you are right handed, as you shoot, your neck muscles are tight. then as you squeeze the trigger, your neck muscles relax which allows the butt to move to the left a whisker which, in turn shifts POI to the right. this was an issue that I was picked up on but didn't realise.
 
Do you have external turrets? Could you have bumped the windage?
Also, mirage, water vapor could move your image.
Id say recheck everything. Try a 200 yard target then 400.
 
Shot this group yesterday 1st pic. Shot same load today after zeroing at 100yds 2nd pic
What distance were you zeroed at for the first picture? How many clicks @ 1/4' per click did you adjust your windage for when you then zeroed at 100 yards? Another words what changes did you make between your two groups of 400 yard shots?
 
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Scope is canted to the right WRT BORE centerline. You can level the gun all you want before installing scope, but in most cases, nothing on the receiver has any positional relationship to the barrel. Put tape on mounts & scope tube, loosen the scope rings, rotate the scope a bit to the left, tighten it down & RE-fire.
Interesting, but scope canting has a diagonal effect on trajectory. I'd like to know what changes OPer made when he sighted in at 100 yards between his two 400 yard groups.
 
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