Range Report Bullet drift issues??

[mgd45]

Has anyone had any experience with bullets drift when there is literally no wind?? I have been slowly developing drop data for my Dept. rifle (Rem 700P) over the last year. I have shot in 50 yard increments out to 1000 yards with a 100 yard zero.

My drop data for 400 yards is 8.0 moa up. I went shooting yesterday and decided to shoot at an old colored bullseye target (on a 8.5 x 11 sheet of paper) from 100 to 500 yards in 50 yard increments.....one shot at each distance.

It was perfect weather! There was nothing, nada, zip, in the way of wind. My first shot at 400 was about 4 inches high but hit about 6 inches to the right. I never felt or saw any wind & I'm shooting in a field where my shooting lane is surrounded by trees on both sides.

I figured it was me with the round hitting to the right. I made a 1 moa adjustment down & fired again. The round hit bullseye level, but again hit 6 inches to the right. CRAP! This time & made a 1.5 moa adjustment to the left & fired. Bullseye!

There was never any wind blowing at all.....none of my little flags were moving between me and the target.....& no movement at the target. What the hell??? Does anyone here experience bullet drift at such a short distance? I know it can't be the bullet really drifting at only 4oo yards....

I was shooting with the bi-pod on the hood of my Jeep with a rear sandbag. There is a slight hill in the ground that makes the target invisible at that distance. Maybe it was my shooting position.......I know it's not the best position, but I really felt stable & I placed one of my Bi-pod feet in the hood vents to keep it from sliding.....

 

[rijndael]

Re: Bullet drift issues??

Are you certain that you weren't canting the rifle, and that your reticle is also level (tracking vertically)?

http://www.microlevel.biz/cant_errors.html

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Suppose we sight in our favorite varmint rifle to be dead on at 200 yards. That is a pretty good zero to cover the close targets. With target adjustment knobs, we can click up as required when shooting at longer ranges. For example, let's say we see a sod poodle way out yonder at 500 yards. We know the range because we used a laser rangefinder. Let's further assume there is no wind (humor me, OK), so we click our scope up 36 clicks to raise the bullet trajectory as needed to hit the target.

We carefully caress the trigger, all the while expecting red mist. But instead, we see brown dust. How come? Well, suppose the vertical crosshair of our scope was canted just 5°. Moving the impact up 36 clicks creates a horizontal error of 1.5 inches at 200 yards, or 3.75 inches at 500 yards. (Note: 36 clicks at 200 yards is 18 inches, and 1.5 inches is half the horizontal displacement of our 36-inch yardstick example.) And, just like shooter-induced canting, the effects get worse with increasing range. The same effect occurs when making windage adjustments, only the effects are reversed: the elevation moves more than the horizontal.</div></div>

 

[JRose]

Re: Bullet drift issues??

I dial .2 mils in from my 100y zero when shooting 600y. If I don't, I consistently hit to the right a bit.

 

[BOLTRIPPER]

Re: Bullet drift issues??

my money is that the reticule is not plumb....

some purposely cant the reticule to the left so as to compensate for the long shots ...say past 600yd and beyond.....even shooting a much more forgiving bullet with a higher BC....

i have found that to make comparisons one must always do the most stable of shooting positions likely found in the field.....that would be prone podded and bagged.

 

[gtofan]

Re: Bullet drift issues??

I know you said there was no wind, what about at 100 yds out or even 300? Shooting at 200 yds is hard enough when shooting for score without some windflags.

You will be surprised what happens with the wind downrange, an imperceivable amout of wind can knock a bullet off the target at 600 yds. I'm using high BC boolits at 200 and a 5 mph wind is out of the 10 ring.

I would invest in some windflags and try it again.

 

[Greg Langelius *]

Re: Bullet drift issues??

This is why I never put much faith in wind charts/formulae.

Felt wind is only useful at short distances.

Just because you don't observe wind telltales doesn't mean they're not there. It can be dead calm along the sight line, but as distances increase, so do the ballistic arcs, and winds aloft can be causing drift while surface winds are nil.

Remember, you are shooting through a three dimensional volume/medium, which has internal flows that may or may not be visible to the human eye, aided or unaided.

Greg

 

[81STFACP]

Re: Bullet drift issues??

Shoot at 50 yards on a target with a vertical line that is plumbed straight and dial every sight setting to 1K, shoot at the same aiming target at the bottom of the vertical line and see where your shots land against the straight line.

 

[dj70]

Re: Bullet drift issues??

Ahhhh.....Kentucky Windage, some people got it, some don't.

 

[Grump]

Re: Bullet drift issues??

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I placed one of my Bi-pod feet in the hood vents to keep it from sliding.</div></div>

Repeat the exercise with that variable removed. With the plumbed vertical tricks posed above as well.

You may have altered the recoil dynamics during barrel time. I'd guess left leg, but would have to play with the rifle and look at the balance points to give a truly informed opinion. FWIW.

 

[mgd45]

Re: Bullet drift issues??

I've been without a home computer so forgive the slow responses. I forgot to add that I was shooting .308 168 grain TAP ammo and my goal was to take one shot at each of the distances using my previouosly obtained drop data.

This is almost exactly to the day last year that I obtained my 100 yd. zero and the weather is virtually the same.....beautifully perfect spring weather. It's possible that I might have canted the rifle a tad bit, cuz I do have the Harris bi-pod that cants.....but I really focused on not having it canted.

It's also possible that there could've been a slight puff of air between me & the target......but it really was imperceptable if it was there. I was just wondering if anyone else has to dial in windage along with elevation when shooting that far even when not detecting any wind.

I never had to dial in any windage at 300 & 350......it was dead on....only when I got to 400. Of course, those other shots were taken prone to, not standing & leaning across the hood of my Jeep.....

 

[gtofan]

Re: Bullet drift issues??

I didn't pay attention to your last sentence, like Grump said, repeat the test....place a piece of carpet or rubber mat under the bipod and try to reduce as much as possible the "hop"

I wouldn't use the hood.

 

[Gogetum]

Re: Bullet drift issues??

My rifle does the same thing and drifts the farther out that I shoot.

 

[mgd45]

Re: Bullet drift issues??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 81STFACP</div><div class="ubbcode-body">Shoot at 50 yards on a target with a vertical line that is plumbed straight and dial every sight setting to 1K, shoot at the same aiming target at the bottom of the vertical line and see where your shots land against the straight line.
</div></div>

So shoot at 50 yards for all the shots? Just dial in the different distances dope that I've already obtained......? I guess this will help determine if my scope is tracking correctly the more I dial up? Is that the point here? Thanks for the suggestion.

 

[gtofan]

Re: Bullet drift issues??

Also if you are getting bipod hop the barrel is twisting over and will surely send your shot wherever.

Or don't use the pod and place in a solid front rest, remove as many variables as you can.

 

[81STFACP]

Re: Bullet drift issues??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mgd45</div><div class="ubbcode-body">
So shoot at 50 yards for all the shots? Just dial in the different distances dope that I've already obtained......? I guess this will help determine if my scope is tracking correctly the more I dial up? Is that the point here? Thanks for the suggestion. </div></div>

Yes... scope tracking correctly and will highlight cant you don't know you have...

 

[mgd45]

Re: Bullet drift issues??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 81STFACP</div><div class="ubbcode-body">

Yes... scope tracking correctly and will highlight cant you don't know you have... </div></div>

Thanks for the advice. I'll try it this weekend.