Range Report two different calibers - one zero ?

[gunshinestate]

I have my scope (on AR) zeroed for a .223 Nosler 60gr at 50 yards. -
I am going to place this scope and mount on a Remington 700 - .308 and shoot this weekend.
I've searched around without any luck trying to find a ballistic program that would allow me to enter in the AR zero/round info and then enter the .308 data and be able see both trajectories on a graph.

Can anyone suggest a program to look for? Or, if anyone has a few minutes, would you mind punching it up?

I am ultimately trying to find what range the .308 will be zeroed when the scope is set at a 50yrd zero for the .223?

I feel like this should be pretty easy but for some reason, it's just getting lost on me. I'd appreciate any help/info I can get.

Info -
AR -scope height is 1.47" -
.223 Nosler partition 60 gr
BC .228 -
velocity 3160

700
scope height 2.5"
.308 SMK
168 gr bthp
bc - .447
vel - 2650

 

[Captain Kirk]

Re: two different calibers - one zero ?

A optic will never be in mechanical zero when sighted in on a rifle, too many variables. There is no way to "know" where your bullet will impact when you switch optics/rifles. What you can do is mount the optics on your 308 and fire it, make note to the elevation and windage adjustment changes and document it, this will effectively allow you to reset the zero and turrets when you switch optics.

Hope thats what your looking for.

Kirk R

 

[TOP PREDATOR]

Re: two different calibers - one zero ?

^^ what the Capt said.

with a little work, if your optic has resetable turrets, you can try to zero in with one rifle. set turrets to 0, just as long as your optic is using QD rings and you have a rail on both rifles. also thing about the height above the bore and cheek weld.

then swap it to the other rifle, keeping track of your "lefts and rights & ups and downs" to your "new" zero, reset the turrets.

when swapping back to the first rifle just do the opposite in "lefts and rights & ups and downs" and reset the turrets.

in other words, for example on your .223 you are zeroed, but when you swap to the 308 you have to adjust to "20 clicks" up and "12 clicks" right on your turrets (whatever the corresponding # would be). put the optic on the .308, make the adjustments and you should be fine.

swapping back to the .223, adjust 20 clicks down now, and 12 clicks left. (note the corresponding number there too so you don't have to count clicks)

then shoot your seperate dope for each.

it'll work, but you will have to keep good records of where you are at in the process.

i do a similiar deal when switching from one load to another for different hunting seasons and using different ammo, no problems, but that is with the SAME caliber.

 

[gunshinestate]

Re: two different calibers - one zero ?

TopPred - that's exactly what I was hoping to do.. keep good records and switch/reset to listed zero.
It's an ADM QD mount so I should be getting close to repeatable.


I was hoping to have a good idea on what distance to start shooting the .308 and hitting paper, then adjust out to 100 to figure out the zero.

So, I shoot my .223 and it's zeroed at 50 yards.. the bullet goes up and come back down, crossing the zero line at roughly 200 yards. I was thinking that if I put the scope on the .308 and shoot it, somewhere between the bore and the 100 yard line, the .308 round will intersect with line of sight of my scope (the AR's zero). Maybe it would be at 67 yards, maybe it would be at 83, etc. (just picking numbers). If I could figure out, on paper at least, where that .308 round will intersect with the scope's poa, then I could setup the target there, confirm, then walk it out to 100 and dial in zero.

Example, using your numbers from above, say my .308 would be 20 clicks high at 100 (again, just picking numbers), I wouldnt even be hitting paper, hence having no idea where to adjust the scope. If I could at least figure out the point at which the .308 will intersect the .223 poa, it'll save me a hell of a time and ammo. Right?

 

[Captain Kirk]

Re: two different calibers - one zero ?

Mount it on the 308 with the optic still zeroed for the 223, remove the bolt and look through the bore at a suitable target @ 100 yards, this will tell you where POA/POI variation is. Using this method you should be able to get on paper in one or two rounds, and remember to document it!

Your trying to over think a mathematical equation when you don't have all the variables yet, once you know what the zero is on your 308, you already have the zero on the 223 so you can repeat it back and fourth.

Kirk R

 

[gunshinestate]

Re: two different calibers - one zero ?

I'll give it a try.

Thanks everyone.

 

[CanSniper]

Re: two different calibers - one zero ?

Other things play a role in a good zero, besides bullet drop. Machine tolerance and barrel harmonics effect zero at 100 more the drop.
There is no way to calculate these other than shooting paper.

 

[azimutha]

Re: two different calibers - one zero ?

Even if you just want to look at the graphs you can copy the data into Excel if you have that.

 

[MitchAlsup]

Re: two different calibers - one zero ?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: GunshineState</div><div class="ubbcode-body">So, I shoot my .223 and it's zeroed at 50 yards.. the bullet goes up and come back down, crossing the zero line at roughly 200 yards.</div></div>

If your 223 loading is in the 3000 fps range it will be at its highest (level sight line) at 75 through 100 yards. From there it will drop.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I was thinking that if I put the scope on the .308 and shoot it, somewhere between the bore and the 100 yard line, </div></div>

Note that a 0.001" machinining error in the mount of either gun will move the PoI at least 1". The error could come from the machining of the barrel, the mount, the riser for the scope, or any combination of the these. So, you simply shold not operate under the assumption that you can move a scope from gun to gun. In addition, you should know that simply removing a scope from a gun and then reattching the same scope to the same gun wiht the same bolt tension can move the PoI at least 1" at 100 yards, too.

If you want accuracy, use one scope per gun. And when it is set up, don't fiddle with the attachment.