Range Report Math question - QD scope from .308 to 22LR

[gannon145]

I'm bored and got to thinking about the math behind moving my .308 scope (on bobro QD mount) over to my 22LR trainer. I just wanted to post my thoughts and see if you all agree or disagree with my math. I have no idea if this concept is sound or not.

By calculating ballistics with a 0 yard zero and 0 sigh height, we get the cartridge ballistic drop from 0 yards to infinity..

<span style="font-weight: bold">For .308</span>
Range Elevation Elevation
(yd) (in) (MOA)
0 0.00 0.00
50 -0.63 1.21
100 -2.60 2.48
150 -6.00 3.81
<span style="font-weight: bold">200 -10.93 5.22</span>

I have a 200 yard zero on my .308, so my scope is zeroed at 5.22 MOA to meet the drop of the .308 cartridge.

Applying that to the 22LR table:

Range Elevation Elevation
(yd) (in) (MOA)
0 0.00 0.00
5 -0.04 0.72
10 -0.16 1.48
15 -0.36 2.24
20 -0.63 3.01
25 -1.00 3.79
<span style="font-weight: bold">30 -1.44 4.57
35 -1.98 5.37</span>
40 -2.60 6.17
45 -3.30 6.98
50 -4.10 7.81


If I do a direct swap, my zero on the 22LR should be somewhere around 30-35 yards.

However, I have a 20 MOA base on my .308. So I would need to dial 20 UP just to get to the 30-35 yard zero.


This seems to simple to be correct, what am I missing?

 

[turbo54]

Re: Math question - QD scope from .308 to 22LR

That should be correct, assuming the 20moa base is actually 20moa, and assuming the scope tracks, and the mounts are repeatable, and the receivers are parallel to the bore etc etc etc.

 

[The Mechanic]

Re: Math question - QD scope from .308 to 22LR

Nothings perfect. You just need to set zero for either one and then dial in correction for the "other" rifle or rifles. Piece of cake

 

[jwp6114]

Re: Math question - QD scope from .308 to 22LR

this is why i love the shooter APP, just mount it up on any gun set at zero from your host rifle and tell the program the error. then it can calculate any dope for that second rifle, i use 2 NF scopes on about 5 guns.

 

[waste_knot]

Re: Math question - QD scope from .308 to 22LR

JWP, Where do you enter the offset error. In the firearm profile?