• If you are being asked to change your password, and unsure how to do it, follow these instructions. Click here

REALLY OVERTHINKING 0 moa / 20 moa rails

W

wilehunting

Well-Known Member
Joined
Mar 18, 2023
Messages
90
Location
Mount Pleasant, Pa.
Work is slow, hunting season is over, some fun out of curiosity,

I've only ever used the standard two piece scope base and ring arrangements, preferably Leupold dual dovetail mounts, on my rifles and a couple of Rugers with their integrated scope rings.

I understand that a 20 moa rail effectively would raise poi roughly 20 inches at 100 yds giving more range via the scope adjustment without holdover at longer ranges. BUT, OVERTHINKING begins…

Since hunters safety education when I was 15, I learned that the trajectory of a bullet crosses the line of sight twice. Once at about 25yds and poi at 100yds. Since the bullet starts to fall immediately after leaving the muzzle there has to be a built in wedge into the rifle for the bullet to "rise" and then "fall" through the line of sight.

So,

a 0 moa picatinny rail is not really parallel to the bore,
I believe the higher the rings are, the more wedge effect is incorporated into the system on any rifle,
a 20 moa picatinny rail is wedge shaped,
a 3-9x40mm in low rings will not have the same ballistics chart trajectory as a 5-25x56mm in super high rings,

I will use the long existing and worldwide used 30-06 shooting a mid weight 165 grain bullet with the popular sized 3-9x40mm scope in medium rings for my questions,

What real affect would putting a 20 moa rail do to the trajectory using a 200yd zero?
Would a 20 moa rail increase maximum point blank range at all?

Thank you
 
wilehunting said:
Work is slow, hunting season is over, some fun out of curiosity,

I've only ever used the standard two piece scope base and ring arrangements, preferably Leupold dual dovetail mounts, on my rifles and a couple of Rugers with their integrated scope rings.

I understand that a 20 moa rail effectively would raise poi roughly 20 inches at 100 yds giving more range via the scope adjustment without holdover at longer ranges. BUT, OVERTHINKING begins…

Since hunters safety education when I was 15, I learned that the trajectory of a bullet crosses the line of sight twice. Once at about 25yds and poi at 100yds. Since the bullet starts to fall immediately after leaving the muzzle there has to be a built in wedge into the rifle for the bullet to "rise" and then "fall" through the line of sight.

So,

a 0 moa picatinny rail is not really parallel to the bore,
I believe the higher the rings are, the more wedge effect is incorporated into the system on any rifle,
a 20 moa picatinny rail is wedge shaped,
a 3-9x40mm in low rings will not have the same ballistics chart trajectory as a 5-25x56mm in super high rings,

I will use the long existing and worldwide used 30-06 shooting a mid weight 165 grain bullet with the popular sized 3-9x40mm scope in medium rings for my questions,

What real affect would putting a 20 moa rail do to the trajectory using a 200yd zero?
Would a 20 moa rail increase maximum point blank range at all?

Thank you
Click to expand...
Most of my rifles has at least 20 MOA regardless if they have enough internal adjustments. All of my rifles are zeroed at 200Y (my preference).
 
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.
 
wilehunting said:
Work is slow, hunting season is over, some fun out of curiosity,

I've only ever used the standard two piece scope base and ring arrangements, preferably Leupold dual dovetail mounts, on my rifles and a couple of Rugers with their integrated scope rings.

I understand that a 20 moa rail effectively would raise poi roughly 20 inches at 100 yds giving more range via the scope adjustment without holdover at longer ranges. BUT, OVERTHINKING begins…

Since hunters safety education when I was 15, I learned that the trajectory of a bullet crosses the line of sight twice. Once at about 25yds and poi at 100yds. Since the bullet starts to fall immediately after leaving the muzzle there has to be a built in wedge into the rifle for the bullet to "rise" and then "fall" through the line of sight.

So,

a 0 moa picatinny rail is not really parallel to the bore,
I believe the higher the rings are, the more wedge effect is incorporated into the system on any rifle,
a 20 moa picatinny rail is wedge shaped,
a 3-9x40mm in low rings will not have the same ballistics chart trajectory as a 5-25x56mm in super high rings,

I will use the long existing and worldwide used 30-06 shooting a mid weight 165 grain bullet with the popular sized 3-9x40mm scope in medium rings for my questions,

What real affect would putting a 20 moa rail do to the trajectory using a 200yd zero?
Would a 20 moa rail increase maximum point blank range at all?

Thank you
Click to expand...
0moa rails are parallel to the bore, it's your sight in process that makes the scope hit where you want it to.

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 rail.

Interesting thought experiment in terms of geometry though you can do the math with triangles to confirm or deny my statement
 
wilehunting said:
What real affect would putting a 20 moa rail do to the trajectory using a 200yd zero?
Would a 20 moa rail increase maximum point blank range at all?
Click to expand...
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.
 
The angle of the scope's body, which is what you change with a canted mount, is completely irrelevant to anything related to the bullet's flight path relative to the line of sight. All it does is move the point in your scope's elevation travel where the scope is zeroed to allow you to use more of the scope's elevation to dial long shots. It has no impact on the angle of the flight oath relative to your LOS, MPBR, elevation adjustments, or anything else. It just lets you use more of the scope's travel.
 
ShtrRdy said:
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.
Click to expand...
Speaking of 'incorrect assumptions'. Where do you guys come up with this 'touches line of sight once' crap? In your 'scenario' the bullet rises thru the line of sight somewhere around 25 yards and drops thru again at 100. Prove me wrong......
 
huntsman22 said:
Where do you guys come up with this 'touches line of sight once' crap? Prove me wrong......
Click to expand...
We come up with it from physics and understanding of a concept called gravity.
IMG_3761.jpeg

www.everydaymarksman.co

Make faster Hits and Improve Marksmanship with Your Point Blank Zero

The point blank zero, also called maximum point blank range, or battlesight zero, is a tool for achieving faster hits on target. But it takes some math...
www.everydaymarksman.co www.everydaymarksman.co
 
huntsman22 said:
Thanks for proving my point.......
Click to expand...
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
 
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 at 200 yard "zero" where it will cross the LOS before that point the first time then gravity drops the bullet over the line of sight, to your 200 yard zero the second time..
 
Last edited:

Similar threads

T
20 moa rail
Replies
5
Views
2K
Broz
B
S
20 MOA rail needed?
Replies
5
Views
1K
ScopeRKT
S
J
Changing from 20 MOA rail to zero MOA mounts?
Replies
0
Views
2K
joseph
J
W
20 MOA RAIL & JBM Question
Replies
10
Views
2K
therichardpowell
T
USAFRet
20 or 0 MOA - Which do you think?
2 3
Replies
30
Views
2K
tim_w
T

Recent Posts

Top