Parallax, 5 to 25 yards, and POA vs POI

Adjusting the AO just puts you on the 8yd plane and negates any paralax error while focusing the scope. You would still be hitting an inch or so below your POA. With a 25yd zero you will likely have a near zero of around 15yds or so. Anything before 15yds will hit low, anything between 15 and 25yds will hit high, and anythything beyond 25 yards will hit low again. These numbers are assuming several variables and I can almost guarantee they don't actually hold true but are basically how a scope works.

Download Chairgun, put in your specs, and you will get a rough idea of your trajectory. 

it isn't so much the trajectory, but rather the fact that your scope is typically ~1.5" above the hole where the pellet comes out.

This is part of the challenge of pesting with air rifles, and very small targets!. If you get one of the ballistics apps, it can show you a chart with the curved trajectory of your pellet compared to the straight line of sight. It's possible to zero your rifle with only a single crossing where the pellet rises and just meets your line of sight where POA equals poi at one point in the entire trajectory. In this case you will have hold over both at ranges shorter than and longer than your zero distance.

This gets very difficult if your scope is set high above the axis of your bore and your pest is at a very close range such as for a close-up kill shot. This is where a range card becomes super handy. You can simply notate the holdover or hold under expressed in mil-dots for every 5-yd distance. A 5 or 10 yard hold over is larger than you think!

You can also zero at a slightly shorter distance and have two zero crossings, where the pellet rises above your line of sight at the first zero distance, is above your line of sight for a short distance, then falls below your line of sight at the far zero distance. This means you must have a chart to show both hold over and hold under in order to hit your tiny pests' kill zones.

I think of air rifles as having about 1/10 of the range of powder burners for instance. If you are shooting long distances in powder burners, you will be forced to learn about trajectory.

My scope is zeroed at 25 yards, AO set at 25 yards. AO adjustable increments, 5yd-25yd-INF.

If left as is, and I aim at a 8yd target, POA bullseye, POI should be low, correct?

If I adjust AO to 8 yds, should this compensate for the low impact and hit bullseye, OR does this only allow for target and reticle to be aligned, and I have to use hold over for closer shots?

I've been shooting fire arms all my life but never even ever had to consider this next one...

So, being zeroed at 25 yards, entry level break barrel, the pellets trajectory may have a little arc.

At 8 to 10 yards I'm not concerned about it, but what if I want to stretch out to 35-40 yds? The hold over will still need to be high, correct? (Like a 8yd target)

Thank you all in advance.

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I took a look in your profile and see you have a 177 Gamo gas piston rifle. I have an older model.

Also saw you were shooting a Crosman 10.5 pellet. The Premier Ultra Magnum? That's the ballistic coefficient I picked to enter into the desktop version of Chairgun.

The stock scope height on my Gamo is about 1.75" (not accurately measured) so I entered that. Kill zone was already 0.5" so I left it at that. Speed in my 177 tab was 900 FPS so I left it at that.

With those specs your Optimal Zero would be 36 yards and you could be 1/4" low at 14 yards and 1/4" low again at 40 yards. At 25 yards you'd be 0.23" high. 

Now I don't know what your scope height is or how fast you're shooting those 10.5 grain pellets but even if I lower the scope height to 1.25" and the speed down to 800 FPS your optimal zero would still be greater than 30 yards.

Now the flip side to the speed, pellet and scope height I selected is that pellet is at its apex right around the 25 yard zero you're currently using. So if I change the zero in Chairgun from Optimal Zero to 25 yards your pellet is 1/4" low at 16.2 yards and 1/4" low again at 34.6 yards.

So with this example you would have a longer "flat" spot within the 1/2" kill zone by having your scope zeroed to Optimal Zero. And that flat spot in this case would start closer to your shooting position, even though you are zeroed further out.

Now if the zero were even closer then you'd have a range of distances in the middle where hold under would be required, which I try to avoid.

My scope is zeroed at 25 yards, AO set at 25 yards. AO adjustable increments, 5yd-25yd-INF.

If left as is, and I aim at a 8yd target, POA bullseye, POI should be low, correct?
At 8 to 10 yards I'm not concerned about it, but what if I want to stretch out to 35-40 yds? The hold over will still need to be high, correct? (Like a 8yd target)

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As others have explained, your poi/poa is not dependent on the AO adjustment, other than you need a clear focus of your target.

IMO,, for a break barrel shooting 800fps, and shooting nutters out to max 40 yards with maybe a 8 yard shot here and there, zero at 20 yards.

Zero'd at 20 yards will give you an almost flat trajectory between 20-35 yards. About 1" low at 10 yards. Remember that almost whatever distance you sight in at there will be 2 zero points.



This an old post By B.B. Pelletier on pyramydair.com. I find it works perfect for me at the same hunting range you use….

"For a pellet gun that shoots around 800 f.p.s., I like to sight in at 20 yards for the near distance. The second distance will be around 30 yards, and the pellet will not rise by as much as one pellet diameter at the in-between distances (between 20 and 30 yards). If you sight in at 15 yards with the same gun, the pellet will be back to the intersection of the crosshairs around 40 yards, and it will rise more than an inch in between.

For a gun that shoots 950 f.p.s., I would still sight-in at 20 yards as the near distance but the far distance is now 37 yards or so. For both guns (800 and 950), the pellet will be about one inch below the aim point at 10 yards and will rise to the crosshairs as it approaches 20 yards. "

jmo

 



This an old post By B.B. Pelletier on pyramydair.com. I find it works perfect for me at the same hunting range you use….

"For a pellet gun that shoots around 800 f.p.s., I like to sight in at 20 yards for the near distance. The second distance will be around 30 yards, and the pellet will not rise by as much as one pellet diameter at the in-between distances (between 20 and 30 yards). If you sight in at 15 yards with the same gun, the pellet will be back to the intersection of the crosshairs around 40 yards, and it will rise more than an inch in between.

For a gun that shoots 950 f.p.s., I would still sight-in at 20 yards as the near distance but the far distance is now 37 yards or so. For both guns (800 and 950), the pellet will be about one inch below the aim point at 10 yards and will rise to the crosshairs as it approaches 20 yards. "



This information is golden!! Obviously, the closer the scope to the barrel the better which A LOT of people don't seem to pay attention too.