REALLY OVERTHINKING 0 moa / 20 moa rails

[biednick]

That was my intention, sorry I was being sarcastic haha

But seriously, gravity has to bring it down and it intersects with the line of departure a second time. This concept is pretty big across the the AR cqb zero conversations with things like 36/300,
50/200 etc

It starts at the line of departure, immediately falls away, and never crosses it. The line of departure is the vector the bullet is traveling on the instant it leaves the barrel, and gravity pulls it down from there. It crosses the line of sight twice, and both rises and falls relative to the LOS.

I'm guessing that's what you meant, but don't want anyone else to read it and get confused.

 

[med358-boise]

Theoretically… the bore and a perfectly optically centered scope on a "0" MOA rail is 1.7"-1.8" different at rest over the chamber AND at your 100 yard target.
You then sight in and lower the crosshairs to match the bore axis at 100 or 200 yard "zero" where the bullet crosses over the line of sight the first time.
Gravity will then drop the bullet back below your line of sight somewhere farther down range for the second time.

However, (with more experimentation)) there is an unknown point where you can sight in to barely get the bullet up to your line of sight and only touch at one point and begins to fall from there.

That is actually a really interesting point. I just did a trial and error on one of my 308 hunting loads and a ballistic calculator. Note it only measures in 1 yard increments and .1 inches so the output you get is an elongated touch point or think of it as an elongated zero distance. For my rifle its ~79 yards. The trajectory output is -.1" at 66 zeroed from 67 to 92 and -.1 at 93.

okay, okay, my inner geek is coming out

 

[wilehunting]

I would like to point out an incorrect assumption you are working with. On a high powered rifle with a scope sighting system, zero'd at 100 yards, the bullet trajectory goes from the muzzle to the optical point of Aim at 100 yards and then drops from there. In other words the bullet trajectory touches the line of sight once.

 

[Roughrice]

You are absolutely correct!
My apologies for misleading on the 100 yard zero!
Beyond 100, depending on the velocity and BC, is what I was trying to point out about crossing the LOS twice.

SORRY ABOUT MY POST!
I have corrected my post on the LOS vs zero!

 

[wilehunting]

Mathematically you're right about the "wedge" (2 non parallel lines) however you're wrong about taller rings. The wedge angle is what's most important, and taller rings do not change the angle of the wedge. By raising the scope 1 inch higher, but keeping the angles the same, you lower the point of impact (assuming you did not adjust the scope) by just under 1 inch at your sight in distance.

This is because your scope is now aiming 1 inch higher because you raised it, but now because you adjusted the distance between 2 non parallel lines the intersect point is slightly further away, reducing some of the affect. But being that your triangle of side length 2 inches by 100 yards has now become 3 inches by 100 yards, you've pushed the intersection back a couple of inches, which is why I said just "under" 1 inch. You have technically adjusted the wedge of your reticle, but your scope remains at 0moa and have not meaningfully changed anything compared to a 20moa

It does absolutely nothing for point blank range, once you sight your scope in you can forget you have the 20moa rail, it just moved your turrets further down once sighted in so you can dial further. That's the only benefit and reason to run them. Most scopes have enough adjustment up that you can safely run a 20moa rail without thinking about it.

Got it, thank you