100 Yards = .167 MOA ... 300 Yards = 2.45 MOA. Wait, what???

[loudandproud]

So,

Just got done with my load development on my 7mm Weatherby. The gun is as follows;

Savage 110 Action
Lothar Walther Barrel, 7mm Weatherby, 1:9" Twist
Badger Ordinance Muzzle Brake (F.T.E)
Rifle Basix Trigger
Bedded Boyds Varmint Thumbhole.

All load development was done at 100 yards. Gun is shooting EXCELLENT! Three 5 shot groups in a row all under 3/8 MOA with the lowest being .167 MOA. I was fricken pumped!

Stuck a target out at 300 yards... and all hell broke loose.
5 shot group 2.45 MOA. Yes... Im serious.
Shot another five shot group. 2.05 MOA.
Went back to 100 yards (thinking my scope let loose).. .275 MOA.

What in the world is going on here? Im at a loss.

It is shooting a 154 SST with RL22 powder at 3120 FPS, 25 FPS extreme spread, 8fps S.D.

Could this be cause by the crown/muzzle brake?

 

[jonbearman]

What scope are you using? How fast are you shooting meaning how many rounds down the pipe in how much time between shots.

 

[loudandproud]

What scope are you using? How fast are you shooting meaning how many rounds down the pipe in how much time between shots.

Scope is a Bushnell XRS FFP. 4.5-30x50

I probably about 1-2 minutes in between shots for each string. 5 minutes in between each string.
Barrel is a heavy varmint contour, 26"

 

[gunsandgunsmithing]

Wind flags????

 

[loudandproud]

Wind flags????

Overcast, 2-5mph headwinds. 45*f.

My .308 shot a .425 moa 5 shot group at 300 yards about ten minutes later.

Gun is bedded and the dispersion is radial, not vertical. Just a big 7" blob of crap. :-\

 

[Immike]

Try some different bullets. (heavier)

 

[LHSmith]

Wind effects....there's more going on out there that you fail to see.....and since you don't use flags , analyzing groups is a guess.
Also, good chance you failed to remove the parallax.

 

[queen_stick]

My first thought is to start your load development over, but do it at 300 yds.

any sign of key-holing in the 300yd targets?

 

[loudandproud]

Wind effects....there's more going on out there that you fail to see.....and since you don't use flags , analyzing groups is a guess.
Also, good chance you failed to remove the parallax.

Like I mentioned before, 2-5mph headwind => I had two flags down range you at 80 yards and one at 250 yards.
As far as the parallax, I thought the same thing until I checked it and shot a follow up group. There was no perceivable crosshair shift over the target.

 

[loudandproud]

My first thought is to start your load development over, but do it at 300 yds.

any sign of key-holing in the 300yd targets?

no signs of key-holing. I might pull the muzzle brake off and shot the 100 yard and 300 yard groups again in order to eliminate any thoughts that the problem might be caused by a concentricity issue causing a destabilization of the bullet.

 

[bheadboy]

I would first check the bullet vs twist, and go to a lighter/shorter one which required less stabilizing than the one you are shooting.

Bob

 

[loudandproud]

Targets in question

 

[CatShooter]

I would first check the bullet vs twist, and go to a lighter/shorter one which required less stabilizing than the one you are shooting.

Bob

+1

 

[Immike]

I would first check the bullet vs twist, and go to a lighter/shorter one which required less stabilizing than the one you are shooting.

Bob

Hi Bob, we are using the 1-9 for the 180 hybrids and vld's. In the 284win and shehane's.

 

[loudandproud]

I would first check the bullet vs twist, and go to a lighter/shorter one which required less stabilizing than the one you are shooting.

Bob

What is the heaviest bullet a 1:9" twist should be able to stabilize? I thought a 1:9 should be able to take the heavier bullets (168-175s and such).

 

[jsthntn247]

Who bedded the rifle. Have you checked it with a dial indicator to see how much deflection your getting? Also check the forend and make sure you have atleast .020 clearance on the barrel.

 

[bheadboy]

I would drop to the 168/175 as you most likely need 8 twist, forget the talk of scopes and bedding, if it shoots at 100 it will shoot longer, just must stabilize the bullet, vld's take more twist

bob

 

[loudandproud]

Who bedded the rifle. Have you checked it with a dial indicator to see how much deflection your getting?

A local gunsmith did the bedding. I have a difficult time getting a measurement in my setup.

That being said, If the bedding was an issue, I imagine it would show up at 100 yards as well as 300 yards wouldn't it?

 

[loudandproud]

I would drop to the 168/175 as you most likely need 8 twist, forget the talk of scopes and bedding, if it shoots at 100 it will shoot longer, just must stabilize the bullet, vld's take more twist

bob

Bob,

Do you think the bullets are being over-stabilized because of too fast of a twist?

 

[Jeremy(WI)]

If your twist is too fast, dropping the MV should help