Scope Adjustment

[ropeNshoot]

I'm shooting a Rem 700 in .300wm. It's got the 5r barrel and the B&C stock. I've got a Schmidt and Bender PMII 3-20x50 mounted on a 20moa badger rail and badger rings. I was shooting at 466yds with Winchester factory ammo. My first three shot group was 3.25" across but landed 18" low and 5" right. At 100 yds .1mil = .36" so if I multiply .36x4.66 (for the distance) I get 1.677. I figured that's what each click is worth at 466yds. Since I needed to raise my group 18" I added 11clicks based on the math above. I fired my second three shot group and it landed 7" high. I made some adjustments and got the next group in the center but is my math way off or do I just not understand how to make a proper adjustment? Why was the second group so high? After the third group, I went hunting and shot a doe at 470yds. One shot kill. I just want to know why my second group was so high. I've had this happen with all of my rifles while making drop charts. Any help?

 

[ropeNshoot]

No takers?

 

[ShtrRdy]

It might be a matter of the distances not being exactly what you measured.

Did you try using the reticle in the scope to measure how many mils the first group was off? That should remove any distance errors.

 

[ropeNshoot]

No. I did not but I thought about that afterward. I was using a Nikon Monarch 800 rangefinder and I'm not sure how dependable it is.

 

[FearNoWind]

You didn't say if your scope is FFP or SFP. Most scopes, including SFP Schmidt-Bender, requires that you make an adjustment (using their data sheet) to convert MilDot spacing for the distance/magnification combination you're using.
I have to wonder if you might not have had it at the "base" magnification when you made your initial series of shots.
Another thing to keep in mind is that, because the bullet path is not mathematically linear, any initial drop chart calculations can be expected to have some degree of error. The only sure way to validate a drop chart is to use it as a guide and edit the data based upon actual range results.

 

[ropeNshoot]

The scope is a FFP model. and all groups were fired at the highest magnification. I should probably be happy that the first shots were on the board and not in the dirt!

 

[Mikecr]

I'd test again. Maybe your scope doesn't adjust exactly .1mil/click.

 

[Bravo 4]

Your focal plane has nothing to do with your turret adjustments...only the reticle spacing if your scope is second focal plane. Which yours isn't so don't worry about it.

 

[Mikecr]

Your focal plane has nothing to do with your turret adjustments...only the reticle spacing if your scope is second focal plane. Which yours isn't so don't worry about it.

He said he added 11clicks, he didn't hold 1.1mil off, so it's an apparent disparity with his scope adjustments.
Like I said, Test it. Verify.

 

[Bravo 4]

Yeah I'm tracking, referring to fear no wind's post.

 

[DocB]

Mr. R&S, If you don't mind my asking sir, did you confirm / perform a 100 yd zero prior to going out to 466 yds? Congrats on your deer at 470!

DocB

 

[ropeNshoot]

Thanks! That's my longest kill to date. Yes, I did check my 100yd zero. It was spot on and I printed two three shot groups under .75" prior to moving out to 466yds.