Importance of scope zero

[Franklink]

Spent a bunch of time with a gun on Saturday. Doped out actual trajectories from 10-55 yards with three slightly different scope zeros. Bored enough today that I played with that raw data on Excel a bit and thought it interesting enough of a visual to share here.

Gun is a USFT that average 915fps with JSB 10.34s. Slow twist polygonal rifled barrel.
Scope is a Athlon Midas Tac in MIL.

x axis - distance in yards
y axis - holdover (expressed as 1/10 of a MIL, ie 22 would be 2.2 mils of holdover or 22 clicks if dialing)

Each of the 3 different trajectory curves are produced by a slightly different zero. In theory, the three curves should be identical but simply shifted on the graph. I suspect the reason they're not identical is multifactorial: due to the reticle having mostly 0.5mil increments (0.2mil from 0 to 1mil and 0.5 from 2MIL down) due the less precise nature of holdover (this data was collected using holdover, versus dialing the turret), and simply human error.

The gray has most of the scope zero in the hold UNDER area. Most FT shooters try to avoid hold UNDER, although I've known a couple who could be competitive using hold UNDER.

The blue and red are the more likely candidates for how I typically like to set up a gun/scope. The difference being as subtle as 3 yards for the beginning of the zero distance (22 yards versus 25 yards).

I find a couple things interesting:

• All three intersect at nearly 24 yards. So, if a guy was to zero his scope at 24 yards, and shoot at 10 and 55 and then plug that info into strelok, he runs the risk of not being aware of the slight hold UNDERs from 25 to 39-40 yards.
• With this particular scope, ranging to the yard from 20-25 is less repeatable than optimal. This makes the blue configuration the best for me. Because that makes 22-25 yards part of my zero range. If I was to use a scope zero that coincides with the red trajectory, I'd have trouble with the 20-25s because 20 yards is 0.6mils of holdover versus 0.2 mils of holdover with blue. On that same vein, 21 yards with red is 0.4mils of holdover, but 0 mils of holdover with blue.
  • (this particular scope is more trustable on determining 45 from 50 from 55 (5yard increments) than it is on determining 1 yard increments from 20-25.)
• A fringe benefit of a initial zero of 22 versus 25 yards (blue versus red) is that my 10 yard holdover is reduced with the blue.

In summary, KNOWING you trajectory (and to a lesser extent comparing how that curve falls on the 10-55 yardages with slightly different scope zeros) is crucial to the field target game. And also knowing your scope's strengths and weaknesses allows you to shift the scope zero to capitalize on those strengths and weaknesses.

Spending time setting up an optimal scope zero pays off during matches. Figuring out where pellets are going to go during practice ensures that they'll go where you want them to go during matches.

 

[PowderBurnt]

I keep my zero at 40 yards. Everything is holdover for the most part. I'm very used to it, even though people tell me that going to a sub 30 yard zero would be better.

 

[Franklink]

I keep my zero at 40 yards. Everything is holdover for the most part. I'm very used to it, even though people tell me that going to a sub 30 yard zero would be better.

Might be worth tinkering and seeing if there's any benefit to a closer zero. Factors like which pellet you're using (10.3s or 13.4s) and scope height and how your particular scope ranges are all at play. Best part of fiddling around with stuff like this is that it's trigger time (practice).

 

[scotton]

An added benefit after glancing at the graph is it looks like more of the blue line intersects with even number holds on whole yardage numbers. Assuming you have the Midas Tac reticle with .2 sub tensions, you would be holding more often on a .2 line rather than a .3 space (if that makes sense). I like to tweak my zero so that the holdovers for the smallest KZ sizes will be as close as possible to a reticle mark instead of a reticle space. I get that yardages aren't always going to fall on an exact yard, but you can get close by shuffling back and forth in the shooter box.

 

[RobBonnell89]

Thanks for sharing. Haven’t got into trying anything like this yet myself. Helps to see it on an actual graph. Always something fun and new to learn.

Happy Shooting,
Rob

 

[RScott]

Spent a bunch of time with a gun on Saturday. Doped out actual trajectories from 10-55 yards with three slightly different scope zeros. Bored enough today that I played with that raw data on Excel a bit and thought it interesting enough of a visual to share here.

Gun is a USFT that average 915fps with JSB 10.34s. Slow twist polygonal rifled barrel.
Scope is a Athlon Midas Tac in MIL.

View attachment 504586

x axis - distance in yards
y axis - holdover (expressed as 1/10 of a MIL, ie 22 would be 2.2 mils of holdover or 22 clicks if dialing)

Each of the 3 different trajectory curves are produced by a slightly different zero. In theory, the three curves should be identical but simply shifted on the graph. I suspect the reason they're not identical is multifactorial: due to the reticle having mostly 0.5mil increments (0.2mil from 0 to 1mil and 0.5 from 2MIL down) due the less precise nature of holdover (this data was collected using holdover, versus dialing the turret), and simply human error.

The gray has most of the scope zero in the hold UNDER area. Most FT shooters try to avoid hold UNDER, although I've known a couple who could be competitive using hold UNDER.

The blue and red are the more likely candidates for how I typically like to set up a gun/scope. The difference being as subtle as 3 yards for the beginning of the zero distance (22 yards versus 25 yards).

I find a couple things interesting:

• All three intersect at nearly 24 yards. So, if a guy was to zero his scope at 24 yards, and shoot at 10 and 55 and then plug that info into strelok, he runs the risk of not being aware of the slight hold UNDERs from 25 to 39-40 yards.
• With this particular scope, ranging to the yard from 20-25 is less repeatable than optimal. This makes the blue configuration the best for me. Because that makes 22-25 yards part of my zero range. If I was to use a scope zero that coincides with the red trajectory, I'd have trouble with the 20-25s because 20 yards is 0.6mils of holdover versus 0.2 mils of holdover with blue. On that same vein, 21 yards with red is 0.4mils of holdover, but 0 mils of holdover with blue.
  • (this particular scope is more trustable on determining 45 from 50 from 55 (5yard increments) than it is on determining 1 yard increments from 20-25.)
• A fringe benefit of a initial zero of 22 versus 25 yards (blue versus red) is that my 10 yard holdover is reduced with the blue.

In summary, KNOWING you trajectory (and to a lesser extent comparing how that curve falls on the 10-55 yardages with slightly different scope zeros) is crucial to the field target game. And also knowing your scope's strengths and weaknesses allows you to shift the scope zero to capitalize on those strengths and weaknesses.

Spending time setting up an optimal scope zero pays off during matches. Figuring out where pellets are going to go during practice ensures that they'll go where you want them to go during matches.

You stated the scope zero very well, i.e., "zero starting at 22 yards" or "scope zero from 22 to 40 yards". Someone who says they zeroed at 40 yards doesn't know if they have zeroed it like your blue line or potentially with a zero holdover from, say, 40 to 53 yards.
My Sightron SIII 10-50x60 seems to work great when setup for a zero holdover at 30, 35, and 40 yards.

Your scope sure seems unusual that it is good at the 45 vs 50 vs 55 yard distinction but suffers in the 1 yard increments in the 20-30 yard range.

 

[Franklink]

You stated the scope zero very well, i.e., "zero starting at 22 yards" or "scope zero from 22 to 40 yards". Someone who says they zeroed at 40 yards doesn't know if they have zeroed it like your blue line or potentially with a zero holdover from, say, 40 to 53 yards.
My Sightron SIII 10-50x60 seems to work great when setup for a zero holdover at 30, 35, and 40 yards.

Your scope sure seems unusual that it is good at the 45 vs 50 vs 55 yard distinction but suffers in the 1 yard increments in the 20-30 yard range.

Yeah it's common for guys to state their zero but there's typically a range of zero holdover required. And that "30 yard zero" could be the beginning or the end of the range. And where that range of zero falls in the 10-55 is important.

The Midas Tac has really clear glass, my favorite general use scope. But between my eye disease and the scope being a first focal plane, the depth of field isn't optimal for field target, especially at 16x. I can repeatably range by focus down to the yard from 10-19ish, but 20-25 is a little less repeatable. Past that, I'm happy with 5 yard increments. There's also the general nature of match difficulty. It's entirely possible to encounter a 1/2" kill zone at 21-23 yards in a match, but most of the kzs out at 50-55 are gonna be more like 1.5." With a good wind read, shooting a 50 yard target as a 55, or a 55 yards target as a 50 will still keep the pellet in that 1.5" kz. So the point of all of this was that I shifted my zero range a just a bit closer so that I won't miss a 1/2" kz target when I range it as 23yards but it's actually 20 yards. The holdover difference between red and blue in my chart would be a miss in that example.

 

[Motorhead]

Lol ... while a practice a different miens to achieve a definitive Zero range, once done the POI to POA results are stellar 10 to 55 in the Field target game I play.
At a level of play where one can live & die by the accuracy of there D.O.P.E. information used, learning that scope height, velocity consistency, pellets BC and especially a scopes sub tension scaling is finely calibrated so the data one uses for distance correction is never in question !!!! So one can concentrate on other factors prior to taking the shot over and over again threw out an FT match. Close enough seldom works out !!!

 

[Franklink]

Lol ... while a practice a different miens to achieve a definitive Zero range, once done the POI to POA results are stellar 10 to 55 in the Field target game I play.
At a level of play where one can live & die by the accuracy of there D.O.P.E. information used, learning that scope height, velocity consistency, pellets BC and especially a scopes sub tension scaling is finely calibrated so the data one uses for distance correction is never in question !!!! So one can concentrate on other factors prior to taking the shot over and over again threw out an FT match. Close enough seldom works out !!!

It's just a way of hedging my bets Scott.

For example, the holdover difference between 50 and 55 is 0.2 mils, with either my blue or my red zero range. 0.2 mils at 50 yards is 0.36" and 0.2mils at 55 yards is 0.3963". A 5 yard ranging error either way will still put it in a 1.5" kill zone. I can live with that, target will fall if i read the wind right.

In contrast, if I range a 23 yard target as 20 yards I'm looking at a difference in holdover of
0.5 mils with the trajectory that corresponds to my red zero range. 0.5 mils at 20 yards is 0.36 inches and 0.41" at 23 yards. If that 20/23 yard kill zone is 0.5", ive got much less wiggle room in ranging error to still make that target go down.

So, say I use my blue zero range (which is how I have the scope set up now and how I'll be using it). If I range a 23 yard target as 20 yards, I'm now working with a difference of 0.2mils between those corresponding holdovers. 0.2 mils @ 20 yards is 0.14" and @ 23 yards, 0.2mils is 0.166." For the same theoretical 0.5" kill zone at 20-23 yards, ill take the margin of error here versus with the trajectory from the red zero range.

Seeing how much difficulty I was having with repeatability with ranging by focus on the 20-25yard ranges during practice, I knew I was gonna have some trouble if I left it with that zero starting at 25 yards. I'm much more confident in the setup and trajectory curve versus my scope and eyes ranging ability with a zero starting at 23 yards, for all of the reasons listed above.

I only shared because I found it interesting. First time I've ever worked out actual dope with three slightly different scope zeros like this and I found it educational and perhaps beneficial for others. This is all part of the project of setting up the USFT for Hunter class. Figure I might as well optimize it since I started with a new scope on the gun to be able to shoot in Hunter.