Home Forums Hunting & Shooting Ask The Gunwriters Why would a rifle shoot 1/2 MOA at 100 and 2 MOA at 200 yd???

I recently bought a nice, lightly used rifle and a higher end used scope (separate purchases). My first 2 range trips showed a lot of promise with every hand load I tried shooting 1.25" or better at 100 yd, and several shooting 3/4" or better for 5 shots. Yesterday I moved out to 200 yd with a load that had shot very well previously at 100yd and things went haywire. I shot 8 shots and had a 5" pattern. Frustrated, I moved back to my 100 target and rattled off a 4 shot group just under 3/4".
I left puzzled and ran to my local shop and picked up a box of factory ammo to try. Today I went back to the range with my brother to let him shoot it and eliminate me as a variable. His 1st group at 200 yrds was 3.5" with my hand loads, then he shot another 3.5" group with the factory ammo. Then I shot the factory ammo at 100 and it went into an honest 1/4" group!!! Then I shot the factory ammo at 200 at it was about 3", so we packed it up for the day.

I'm looking for suggestions and help. I have my theory on the problem, but I'm looking to the brain trust here for answers. Nothing really makes sense. HELP!!!!!

Scope parallax or wind would be my first guesses.

Canted reticle??

A canted reticle won't cause it, but tilting the rifle different ways from shot to shot will.

As will parallax and wind, as centershot pointed out. The effect of wind-drift doesn't just double at twice the range: Instead it basically quadruples.

My guess too is parallax. One can even have a reversal. Garbage at 100 and then a tightening when stretched out.

Any pattern to ones dispersal? Vertical, horizontal, or pretty much circular?

I'm pretty sure I can rule out the rifle tilt and the wind was less than 5 mph on both days, so that is out too. I'm assuming parallax issue, which we tried to adjust that prior to the 2nd day of shooting, but it didn't seem to help.

The 2 groups my brother shot yesterday were almost vertical, but mine were all over the place......

According to this article it has the same effect ...

https://www.shootingillustrated.com/articles/2016/3/28/rifle-scope-reticle-cant/

country 20boy,

I'm guessing there's something gone wrong with the parallax, for whatever reason. Vertical stringing is often a sign of excess parallax, because the comb of the stock tends to keep our eye in vertical line with the reticle, but not so much up and down, unless we have a really firm cheek weld.

Parallax seems to be the consensus. I'm going to swap some scopes around later this week and try again. I'll keep you posted, but it looks like this one is headed back to Oregon for repairs......

You answered your own question, think about it...

I always get bigger groups as the range increases. When it quits being MOA moose I have reached my max shooting distance. I respect guys that can hold small groups past 300 yards, wish I could.

Country 20boy, isn't this much better than starting a thread in "Hunting Rifles" just to let Big Stick prance around schitting all over it?

I find it interesting that nowhere does the OP state what caliber, bullet, rifle make and model, scope make and model and the automatic consensus is parallax due to one guy stringing and the next shooter shotgunning. I can think of a bunch more variables to throw in from shooter to shooter than parallax.

Amen......

ya kinda would like to know more details too ? brand rifle ? bolt action,pump or semi auto ? brand and power of scope ? cartridge used ? brand of ammo ? brand of scope mnts. ? what kinda rests were you using ? maybe a picture too ? you want answers we need better info ? some us can help you

I intentionally left out a lot of info, so that no one would jump to conclusions based solely on the brand names...... I also didn't want to point fingers at anyone who may have sold me a junk scope or rifle......and I'm still not.

But here you go:
Nosler M48 in 7mm-08
Leupold VX-5HD
Talley rings
Handloaded bullets were 150 ELDX with RL-15 powder
Factory ammo was Fed. Premium 140 NBT

Rifle was on sand bags, front and rear. Same as I've done hundreds of times with a dozen different rifles.

Believe me, after my Saturday range session, I was questioning everything. That's why I brought along another shooter on Sunday and grabbed some factory ammo. Trying to eliminate 1 variable at a time......
I'm usually a pretty decent bench shooter and I've never seen anything like this. My other guns always hold about the same relative group size. I.E., 1/2" groups at 100 = 1" groups at 200 and 2" groups at 400....

If you have any ideas or suggestions, I'm listening.....

Me too. One factor may simply be that there's too few groups to draw any particularly meaningful conclusions.

The issue with parallax that I see is that any error attributable to it, on the given facts, is likely to be small. If we take it that the rifle shoots well at 100 it seems likely that parallax isn't an issue at that distance. If it is more or less parallax-free at 100 then the maximum error attributable to parallax at 200 is about 1/2 the diameter of the objective lens, for an eye at the extreme edge of the exit pupil. That is about 0.4 moa maximum, for a 40mm objective lens. If we allow for a shooter whose eye position is so inconsistent that they go from one extreme edge of the exit pupil to the other between shots we could add up to 0.8 moa. That is the extreme case though, and would be a technique issue at least as much as a scope issue.

It may be a factor, I guess. I suspect that it isn't the whole story, nor is it the only possibility.

thanks thats a nice rifle and equipment, i wonder: try a different scope on this rifle 1st ? if that don`t help send that rifle back to Nosler that barrel is bad i think ? 7mm-08 in that rifle should shoot 1/2 inch easy at 100 yards, my 7mm-08`s all do, and less or atleast 1 inch at 200 yards. that`s just wrong sorry . i had a new Cooper that did the same thing so i called Cooper they took rifle back and replaced barrel ,now it shoots great. call Nosler,good luck,Pete53

What magnification were you shooting at? If it's a variable, did you try dialing it down to 6x or so to lessen the effect of parallax?

Also, inconsistent MV's are more likely to open up groups as distance increases.