Questions about parallax on my rifle's red dot scope

[gunsrfun1]

I have a Vortex Venom RDS mounted on my Ruger PC carbine. I have two questions about it. I think they are completely unrelated, so I will ask them separately:

1) I had it mounted directly on top of the integrated receiver top rail and had it zeroed to POA/POI. Now I have added a riser, so the scope now sits about an inch higher. Since I have raised the height of the red dot scope, I assume I must re-zero it, correct? (At least the elevation; maybe not the windage.)

2) If I zero it to POA/POI while keeping the red dot in the approximate center of the glass, my understanding is that, in theory, as long as the red dot is anywhere on the glass when I shoot in the future, it should still shoot POA/POI. So if the dot is a bit high, low, left, or right of center-of-glass when I am aiming and shooting, it should still hit what I am aiming at, even though I zeroed it while the dot was in the center of the glass. Is that correct?

Thanks

 

[Varminterror]

1) Yes, you’ll need to rezero. It’s a few shots with a rifle it seems you purchased with intention to shoot, so no harm, no foul there.

2) Yes, ish. Typically there is very slight POI drift as the dot is floated around the window, but also typically not significantly such it makes any actual influence - since red dot sights inherently are not built to be the most precise of sights in the first place. Certainly less drift than floating the front blade of patridge sights within an oversized rear sight notch.

 

[C-grunt]

Some red dots have more parallax issues than others. The first gen Trijicon MRO was pretty bad at the extreme edges.

I dont think Ive ever seen a test with the Venom.

 

[gunsrfun1]

Thank you all, great info as usual from THR.

 

[koz4guns]

After you sight in the dot after reinstalling it shoot a group on paper with one shot centered in the window and one shot each at the extreme edges top, bottom, left and right. If they all land in one group you will know how much parallax will affect your dot.

 

[jmorris]

After you sight in the dot after rising it shoot a group on paper with one shot centered in the window and one shot each at the extreme edges top, bottom, left and right. If they all land in one group you will know how much parallax will affect your dot.

I generally just set the rifle on target in a good rest and let it and the scope sit there while I move my head around. Watching movement of the aim point relative to where I put it with my head in the correct position.