Change in horizontal zero when dialing in??

[Dan B]

I've been doing a lot of dialing in from 100 yds to 500 yds in practice trying to get used to this style of shooting. I'm using a Rem XP-100 .222Rem Mag Imp w/ 52gr A-Max's at 3200fps. Using the Excel sheet from Dave King I got all my MOA dial-ins and been having a ball!! The vertical is dead on to 500 yards...perfect! But as I go out and dial in for each distance from my 100yd zero...the shots are walking to the right. At 200yds they are about 4" to the right, 300yds is about 8", 400yds is 16" and the 500yd groups are about 24" to the right. The groups are good for a beginner...2" at 300yds, 3" at 400yds and grow to about 6" at 500yds. I've also been watching the wind...but it does this is all conditions...calm or windy.

I have a few other LR set ups in both rifle and handgun that are NOT walking as the scope is dialed...only this one seems to do it. The scope looks to be mounted straight (not canted but I'm terrible trying to get a scope straight)...the scope is a Burris 3-12x32 EER w/ target knobs and PA. It's mounted on a Weaver base w/ Burris steel Signature Zee rings.

Any ideas?? Thanks.

 

[Shawn Carlock]

Dan,

Is the reticule square with the target turrets?

 

[RBrowning]

Reticle out of plumb can certianly cause this, but with any light weight firearm recoil can cause this too, espcially a pistol. None of use are mechanical vises and we all allow the rifle to recoil. How the rifle is fitted to our shoulder, or in your case the way you grip the pistol is going to effect the way the gun moves due to recoil. How strong your hand and wrist are, how your elbow is flexed, the weight of your arm all are mechanical elements that can be adjusted to help work this out. I'm not a pistol coach so I won't try to tell you what and how to change, but this is a lesson that I learned growing up left handed in a RH family. Every rifle was sighted in by a RH shooter whose body would twist to the right due to recoil. When the lefty shot the shoulder would rotate the opposite direction and I would always have a different zero than anybody else. This was even more pronounced in shooting a pistol comparing heavy bullets hitting higher than lighter bullets. Everything in the charts says this should be the opposite. But the charts are only considering the bullets flight out of a non-moving barrel. In the real world the heavy bullets were slower getting started, stayed in the barrel longer and were aimed higher due to my pistol beginning to rise due to the recoil.

Sorry I can't give you an exact answer, but maybe knowing where to look will help you find your answer.

 

[Dan B]

Yes...it appears to be square. I may try another scope if I can not get this worked out.

 

[Bart B]

Mr. Browning, I applaud you for noticing that southpaws get a different windage zero than northpaws (right handed) people. And also for being able to figure out the reason is because the barrel moves sideways in different directions before the bullet exits.

I'm convinced that fewer than 1% of the rifle shooters on this planet understand this. One group of people in that 1% group are those who regulate double rifles so both barrels shoot bullets to the same point of aim. They do this by aligning the barrels parallel then putting a wedge between them at some mid point then clamping the muzzles together so their axes cross at some downrange point. That point is closer than the zeroing range. Which means a bullet from a .500 Nitro Express' left barrel goes straight down the barrel for several inches then turns right while really heavy recoil moves the rifle back and towards the left and when the left muzzle axis finally points at the point aimed at the bullet exits when the sights are aligned left of the target. Bullets from the right barrel make a left turn before exiting. So if someone very distraught says their $30,000 Holland and Holland .500 Nitro Express double has both barrels bent inwards at the middle and wants them replaced, you should calm them down and say "they're supposed to be bent that way."

If one's a good enough shot to sight in a rifle standing on their hind legs using only two rounds, they may notice that the windage setting they end up with will be different than what's needed to zero from the traditional 'rifle on bags atop a bench' method.

 

[Bart B]

[ QUOTE ]
Yes...it appears to be square. I may try another scope if I can not get this worked out.

[/ QUOTE ]
Check the reticule and adjustments as follows:

Put a collimator in the muzzle, then zero the scope's adjustment so its reticule centers on the collimiater's reticule.

Look through the scope then turn the E adjustment full range up and down noticing how the reticule tracks the collimator. If the scope's reticule moves off the collimator reticule, the scope adjustments are not aligned with the reticule.

Do this with the W adjustment for windage, too.

If either is off, send the scope back to its maker and ask 'em to fix it.

 

[fishingdude7]

Not that i'm an expert on this stuff or anything, but since your rifle is probably a right hand twist wouldnt that cause the creep? now i'm not saying it should cause this much, perhaps your groves in your barrel are really grabbing the bullet or something, just something to think about from my mind.

 

[RDM416]

Dan,

I had a similar problem though not as pronounced with one of my rifles a few months back. My groups were slowly creeping to right as the range increased, but did not move far enough to be a problem until over 500yds.

As it turned out my scope was slightly canted, although I would have sworn it was straight.

I placed a carpenters string level on the scope rail underneath the scope, and leveled the rifle. Then I hung a plum-bob at 100 yards. Wonder of wonders, my vertical crosshair was slightly out of alingment with the string on my plum-bob.

I also added a B-Square scope level to my rail (which I had to shim to get level)

Now my rifle is level, my vertical crosshair is plumb and my groups no longer drift to the right as range increases /ubbthreads/images/graemlins/cool.gif

It worked for me, so hope this helps.