❓ Setting Scope to its Optical Center —OR— to Max. Elevation Adjustment Range?

In a nutshell it seems that for the ranges the PRS shooters shoot, that might be the norm, but air guns? I know that some air gun shooters are sending out to 300 plus yards. But why? Seems to be more like artillery practice, might be fun, but to what end? Highly impractical because there are no real world applications. IMO being on the extreme ends of adjustments on any piece of equipment is no bueno.

 Generally speaking you want to be in the optical center for best clarity at the range you are shooting the most. if you mainly only shoot at 1000 yards or far enough where you are looking at the optical center while the zero is at the very edge then why not? If you shoot mostly close by the. You want the zero to be in the optical center. 


on top of that every scope has different internal adjustment range so that’s also a consideration. At the end of the day it’s really a long range thing. 


@L.Leon: the question on 300 yards is the same as 1680 yards for the long range guys, why not. You aren’t wrong on there isn’t a real world application for 99% of people besides look at what I can do. However if in the spring I get to shoot Pdogs the long range skills might come in handy. Keep in mind with the 34.8 grain slugs I’ll have well over 20 FPE at 300 yards still. 

@qball, I understand that 34.8 grain slugs might have over 20 FPE at 300 yards. Question becomes whether consistent, humane kills can be made at same distance? Even with center fire .22s, 300 yards is a long poke at small skittish targets.

What a particular person has learned in life becomes him. Most air gunnners learn through the forums that it is best to keep the scope as close to the optical center as possible for life of the scope and clarity. The PRS shooting guy's dial their scopes on target, and take pride in dialing in a long range hit. Both learned a different way to use a scope in life. There are growing numbers of PRS airgunners who like to shoot long distance groups, me being one of those. With scope technology and internal components being held to higher and higher standards, I think that there are a lot more "dialers" in the airgun world now than there used to be, so times are changing.

Dial or not is mainly depend of your rest also do you shoot a single distance or multiple distances in wider range.

First. Me personally I don't like the bipods, I made myself a bench top - tripod setup. So my Impact is pretty much locked down.

When I go to my gun club (5-600+ members private club) usually I chose the ranges with less crowd would that be a 50 or 100 meters or LR22. I set my tripod at that given distance and I dial in the turret, StrelocPro is remembering how many clicks.

Also need to mention that I have a high mounted scope, 82.8mm center to center with 1mm raised at rear. This gives me a lot of elevation adjustments on my X50, I can shoot just anything between 20 and 100 with that in mind I set the zero=center at 60. In this way I am not getting a black ring neither at bottom nor at top. 

That was last year season, now for a new season I am building a one-piece-rest because I am planning shooting 2-3-400 ranges (of course starting with shortest and gradually building it up). With this rest again I can pick my zero distance and pretty much just leave it there.

most prs shooters i know run canted moa rails or mounts so they can both increase their adjustment range, and not have to use the "bottom" of the scope picture.

I just replaced the scope on my FX Wildcat MII. But the time I got it zero'd, the elevation was about maxed out. I was using high rings in a 11mm dovetail/weaver rail, so my optical center was 3" over the bore center. My solution was to move the butt plate lower on the stock 1" and then use low 11mm rings. Now the scope is closer to optical center with plenty of adjustment either way.

If you need more elevation travel you need to raise the scope higher

My answer is that it depends on the scope and application, but as others above have said this push to have the scope at "optical center" when zeroed really seems to be a recommendation only seen on air rifle forums. Go to powder burner forums, especially where longer ranges are frequently shot, and the question is "what cant base do I need for maximum elevation travel out of my scope?" On the powder burner forums you almost never read anything about finding optical center on the scope-- unless someone is wanting to reset their scope to center prior to zeroing it to see how much windage or elevation is needed when they zero the scope if they think they're chasing a scope base or ring issue.

Many cheap scopes don't track very well if you dial for elevation or suffer from very obvious degradation in image quality when not near the optical center... and in that case it's best to use holdovers only and adjust the cant in the mount/rings to have the scope zeroed close to the optical center. I don't mean to be blunt here, but many people put rather inexpensive scopes on their air rifles that often suffer from these kinds of tracking and/or image clarity issues-- and my hunch is this is why we see recommendations on air rifle forums for zeroing the scope close to the "optical center" as the inexpensive scopes many people use on their air rifles work and look best near optical center.

On more expensive scopes that track accurately and repeatably regardless of how far up or down the elevation is dialed, they may still experience optical clarity / image quality or vignetting issues when the elevation erector is dialed very near the upper or lower extremes of travel. For instance, the S&B 5-25s I have on my powder burners will exhibit minor vignetting when dialed within about 5.5 mils of the upper or lower extremes of elevation travel. The Athlon Cronus BTR I have on my Impact M3 will start to lose a little bit image clarity when dialed within about 7 mils of the upper or lower extremes of the elevation travel. I also notice very slight image clarity degradation when dialed within about 5 mils of the elevation extremes on my Premier 5-25s & 3-15s, Minox 5-25s, and Tangent Theta 5-25s. None of these scopes have tracking issues or zero retention issues when dialed near the upper or lower elevation extremes; it's just minor image quality issues that appear, none of which would prevent you from taking a shot... but if you stare through them long enough in those "compromised" ranges of elevation travel it's a bit annoying to the eye.

Because of the image quality issues when dialed near the elevation extremes as described above I try to choose bases that will have the scopes zeroed just above those "image compromised" ranges so I get maximum available elevation travel with no optical issues at the zero distance / elevation setting (i.e. a base that leaves the S&B 5-25s a minimum of 6.5 mils up from the bottom of the elevation travel at the zero range, the Cronus about 7.5 mils up from the bottom, and the Premiers/Minox/Tangents about 6 mils up from the bottom.) Doing so provides maximum elevation up travel from your zero for dialing for longer shots but with no image quality issues at your zero setting. You can of course put more cant in the base for additional elevation travel-- but then you have to deal with compromised image quality when shooting at closer ranges at that zero setting.

Having your scope zereod near the bottom of the elevation range is a bit harder on the erector spring as it’s compressed more-- but that should not matter to a quality scope. If you're worried about excessive compression on the erector spring weakening it over time just dial the elevation turret up when you're not going to be using the rifle for a long time, and dial it back down to the zero setting when you go to use it. Just remember to dial back down to zero before your first shot goes way over the target and you're scratching your head where it might have hit...

@kiba, thank you for a very detailed explanation, backed up with personal experience.

@qball, I understand that 34.8 grain slugs might have over 20 FPE at 300 yards. Question becomes whether consistent, humane kills can be made at same distance? Even with center fire .22s, 300 yards is a long poke at small skittish targets.

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Actually I do think it could consistently perform humane kills even at that distance or pass 200 yards. The reason I say that is at 20+ FPE the hollow point on slugs is not even in the same zip code in term of effectiveness compared to pellets. I've seen it first hand the difference in killing power between HP slugs and pellets on my own hunts. Even on fragile rabbits I've seen center mass shots pellets would not take rabbits down fast enough and it ran long enough to get lost into the bushes. Same caliber slug at same speed rabbits didn't even move an inch. On huge jack rabbits 22 hades simply poked a tiny hole with no pass through but 22 slugs shooting at the same speed blew a big hole right through the small-medium dog sized hares and it just dropped them on the spot. 



At 300 yards connecting on the first shot would be pretty tough but a second shot is still quite realistic as long as the wind is somewhat consistent. And as long as it connects center mass it's a very quick kill at 20fpe with a big HP slug from big jack rabbits to anything smaller. 

@qball, I understand the ballistic specs you present, it's the ability of the shooter to hit and kill humanely at those distances that I question. So many different constantly changing variables... For strictly targets? Air gunners can lob them as far as they see fit and is fun for them.

@qball, I understand the ballistic specs you present, it's the ability of the shooter to hit and kill humanely at those distances that I question. So many different constantly changing variables... For strictly targets? Air gunners can lob them as far as they see fit and is fun for them.

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that is a good point/concern! It certainly isn’t for everyone and does take quit a bit of practice and fine tuning to be able to even get on standard sized paper target. HOWEVER, at that distance the chances of irresponsible shooters even remotely harming a critter is rather low. I would be far more worried about inhumane shots at 30 yards by below average shooters than the few folks who has the ability/know how to shoot pass 200 yards. Just my 2 cents. 



Edit: Just looked at the ballistic data and my impact with 34.8 grain slug has 31fpe left at 300 yards so anywhere center mass is total destruction.