Poor accuracy at 300y, great at 400

[Mr. Magoo]

TL;DR
Do bullets have areas in thier flight path where they destabilize, then re-stabilize and become more accurate?

I have not personally seen this to such a degree in any of my shooting before.

Details:
I've been working on getting a browning a-bolt 7 mag, 1 in 9 twist, sighted in and trajectory mapped. Has a vortex strike eagle 3-18x scope that I pulled off my 308 and has proven rock solid on that.

Heres where it gets wierd. Rifle shoots a hair over moa at 100, 1.5 moa at 200, 2+moa at 300, and .5 to .75 moa at 400. Winds were 5mph and less.

My current life keeps me from having enough time to reload these days, so I'm using factory hornady 162 gr eld-x ammo. Chrono is on perma-loan so I don't know the exact speed of this stuff. Just using hornady data for now.

Not only is it shooting much worse at 300, but it is also shooing much lower at that range than it should. At all other ranges I tested is it right on the money elevation wise when using the hornady app and I was able to get multiple first shot, cold bore hits at 400 and 500 while practicing.

I played around with a bunch of different scenarios assuming my data was off but in no scenario I could come up with does it work out being that far off at 300 and right on everywhere else.

Do bullets have areas of instability that big?

 

[cajun]

Honestly no. What you are seeing is probably the normal variance in the load plus any shooting error magnified by longer ranges.

 

[Phil Rizzo]

I must say, this is a first for Me.
How many times has this scenario occurred ?

 

[Mr. Magoo]

^^Repeated it twice. Yesterday and today. 2 different ranges, both calm days. It hits within 2" of poa at 400 every time, but i would be afraid to miss the vitals on an elk at 300.

 

[Mr. Magoo]

Honestly no. What you are seeing is probably the normal variance in the load plus any shooting error magnified by longer ranges.

I would think the same thing if it wasn't for the fact that I can hit a 4" circle every time at 400 and 500.

I want to try some different ammo, but not sure if time will alow me to get practiced with new stuff before season starts.

 

[Phil Rizzo]

Are you dialing the elevation or using holdover?

 

[Calvin45]

I've heard no shortage of reports of this happening, regardless of what is supposed to be possible. I certainly believe you.

That being said, even if the bullets have their yawing and precession cycle tighten up beyond 300 yards…it's not like they have memory of what direction they were originally pointed and go back to that exactly. I'd have an easier time just accepting this as "going to sleep" if it was a matter of groups not opening up as bad as you'd expect based on 100 yard groups once you're at range. But tightening up? there's gotta be more to this.

Is there any chance this has something to do with scope parallax? Getting a "truer" picture at 400 than 200-300? Cuz that could do this.

 

[Phil Rizzo]

I was wondering if he dialed elevation, and the internal adjustment could have some sort of "bad spot" or range where it was jumping clicks from recoil maybe?
puzzling to say the least.

 

[Barehandlineman11]

If anything it's probably parallax in your scope

 

[cajun]

I would think the same thing if it wasn't for the fact that I can hit a 4" circle every time at 400 and 500.

I want to try some different ammo, but not sure if time will alow me to get practiced with new stuff before season starts.

How many shots total at both ranges? If so something else is going on. Erick cortina and alex wheeler talked about this on a recent podcast. From a pure accuracy and ballistics standpoint it's not possible.

 

[Calvin45]

What targets are you shooting at? Stupid question and probably stupid suggestion but sometimes I just shoot at a target taped to a cardboard box or something. Is it at all possible your 300 yard target is moving around and your 400 isn't?

Again, very stupid suggestion I know…except I've done this…discovering that, even in a slight wind, it doesn't matter how steady I can hold IF THE DANG TARGET ISNT HOLDING STILL

 

[Mr. Magoo]

Wellll, I do check for parralax when dialing.. the marks on the knob aren't necessarily correct but it's close.

 

[Phil Rizzo]

Id have to try another scope. Cant hurt anything

 

[Mr. Magoo]

Are you dialing the elevation or using holdover?

Using point blank to 300 then dialing past that. It SHOULD be around 3" low at 300, but is hitting more like 6-7" low.

You guys are making me think this is a scope issue.