resetting zero

[dead eye kenny]

i have a predator gen 2 american in 400 legend. it has a leupold vx3 with the cds dial set at 50 yard zero. i get confused with ballistics. anyway i ordered a new dial with a 100 yard zero because thats what winchesters ballistic data used for zero. my question is how do i go about zeroing the rifle to 100yards. is it easier to bore site with a laser then shoot? ammo consumption is not an issue, i got an awesome deal on 2 cases of winchester 215 grain powerpoint ammo. i want to zero at 100 yards because i forget that it shoots 1.5” high at 50, with it zeroed at 100 i can hold dead on.
the rifle is a tack driver, awesome firearm.
thanks

 

[Mobuck]

So, your scope is already 'zeroed' with whatever 'dial' you started with? If the scope is 'zeroed' @ 50 yards, most likely the only change would be a bit of elevation adjustment.
Several of the 350 legend rounds I checked showed a mid-range trajectory within +/- 1" with a 100 yard zero. This will likely be covered by accuracy dispersion.

 

[thinckley]

i have a predator gen 2 american in 400 legend. it has a leupold vx3 with the cds dial set at 50 yard zero. i get confused with ballistics. anyway i ordered a new dial with a 100 yard zero because thats what winchesters ballistic data used for zero. my question is how do i go about zeroing the rifle to 100yards. is it easier to bore site with a laser then shoot? ammo consumption is not an issue, i got an awesome deal on 2 cases of winchester 215 grain powerpoint ammo. i want to zero at 100 yards because i forget that it shoots 1.5” high at 50, with it zeroed at 100 i can hold dead on.
the rifle is a tack driver, awesome firearm.
thanks

You're already zeroed at 50. Switch to 100 and adjust the dials, no need to bore sight unless you are changing out the scope.

 

[dead eye kenny]

no same scope. ill just shoot and adjust. thanks. i always get confused

 

[GunnyGene]

https://www.kevinsworkbench.com/scopecalculator/index.html

 

[dead eye kenny]

https://www.kevinsworkbench.com/scopecalculator/index.html

thank you!

 

[GunnyGene]

thank you!

You're welcome. Glad I could help.

My other piece of ballistic stuff I use on-line is the JBM site if you really want to get comfortable with ballistics. It will require some time and study on your part, but it's the gold standard. You'll need to know the distance between the bore center line and the scope center line, the G1 Ballistic Co-efficient of the ammo, and other details. But the program does all the math for you.

https://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi

 

[thinckley]

Another good source is https://shooterscalculator.com/

I use it to find my MPBR for my hunting rifles as I do not want to have to mess with anything (except maybe zoom) when trying to put meat on the ground.

 

[rcs9250]

https://www.kevinsworkbench.com/scopecalculator/index.html

That’s a pretty neat site. Click on “Kevin’s Workbench” at the top of the page for a variety of interesting topics.
Thanks!

 

[GunnyGene]

So, your scope is already 'zeroed' with whatever 'dial' you started with? If the scope is 'zeroed' @ 50 yards, most likely the only change would be a bit of elevation adjustment.
Several of the 350 legend rounds I checked showed a mid-range trajectory within +/- 1" with a 100 yard zero. This will likely be covered by accuracy dispersion.

Given what he said about shooting high @50yds, I'd expect dialing in 3 or 4 clicks up at 100 and then go from there. Without knowing MV of the rifle and ammo G1 BC , can't do more than estimate to get close.

 

[GunnyGene]

That’s a pretty neat site. Click on “Kevin’s Workbench” at the top of the page for a variety of interesting topics.
Thanks!

Yep. the Hard Cider entry is interesting.

 

[Mobuck]

My Cousin says a 100 yard zero with 350 Legend 160-185 grain factory loads results in approx 1" high @ 50. His rifle isn't accurate enough to really discern a variance from line of sight.

 

[dead eye kenny]

thanks for all the info fellas, i appreciate it! i my cousins taught me to shoot during summers spent on the farm, the Marines fine tuned my skills. im a pretty good shot but ballistics just confounds me. seems like i have a lot of homework to do. this is the ammo i shoot. the rifle seems to like it im shooting 1.5” 3 shot groups at 50 yards.

 

[GunnyGene]

thanks for all the info fellas, i appreciate it! i my cousins taught me to shoot during summers spent on the farm, the Marines fine tuned my skills. im a pretty good shot but ballistics just confounds me. seems like i have a lot of homework to do. this is the ammo i shoot. the rifle seems to like it im shooting 1.5” 3 shot groups at 50 yards.

That helps. Plugging that in to JBM, it looks like you'll have about a 3" drop from 50 to 100yds. Subtracting the 1.5" high you have @ 50, that leaves about 1.5" you'll have to compensate for to avoid shooting low. That in turn results in about 6 clicks ( .25" per click) to bring the group up 1.5" . That should get you pretty close, assuming there's no atmospheric conditions you'll have to compensate for (wind, temp, humidity, etc., etc.).

Here's the readout:

 

[kmoore]

I think you're worrying about unnecessary stuff, go shoot at 100yd then dial scope up/down left or right to get you the center. Then loosen up the cap and set it at 100yd zero. Range/trigger time is always good practice.

 

[Rcustom88]

Level the Rifle, Use a small level on the scope rail or a level on the turret cap when mounting the rifle in the bags. Cant (tilt) is the #1 cause of mysterious misses at distance.

 

[thinckley]

Level the Rifle, Use a small level on the scope rail or a level on the turret cap when mounting the rifle in the bags. Cant (tilt) is the #1 cause of mysterious misses at distance.

He's not installing a new scope, he's changing his zero from 50 to 100 yards...