REALLY OVERTHINKING 0 moa / 20 moa rails

[Dirtrax]

What, pray tell, IS the advantage of 'optical centering'? And *** does 'optimal performance' mean? If your scope does not 'perform optimally' while dialling, why even bother having one? Everything below your zero is totally useless, while having more above, lets you play farther.

Others have done a good job of explaining it (thank you koda). Scopes align multiple lenses especially in the case of adjustable parallax. The better they align the better the quality of the image. It's not rocket science.
EDITED to especially.

 

[ARlife4me]

ring height can do 2 things, give clearance for the objective and best focal points. you can have 1 and not the other w/o a cheek riser. keeping as close to the barrel is best. look at your optic specs (lets say 30 moa elevation) it'll give you 300" (25') @ 1k yards. does your cartridge have enough to be within that range w/o adding 20 moa rail (500"+ 41' 9") of drop. on 1 rifle it came with a 20moa rail, then the mount was a 20 moa. 1st thought it would be 40 moa...............nope, it's 400 moa. you multiply it instead of adding. now my 400 moa combined rail/mount + the 120 moa optic has way more elevation than it'll shoot (savage 110 24" 338lm). 5,200" @ 1k is like mortaring it there

 

[wilehunting]

Wrong-O, bucko.....

0 moa rail is as parallel to the bore, as the DD or ruger rings you jabber about.

More jabbering;

While a 0 Moa rail is the same thickness front to rear it is not parallel to the bore. It is simply mechanically & physically impossible. If your scope is 1.5 inches above the bore and the base is parallel to the bore the bullet would never come into the line of sight. Gravity starts pulling the bullet down at 32 ft/sec squared the instant it leaves the barrel.

 

[marc357]

Fellas, I think he's just being deliberately obtuse now.

 

[Huntaddict]

I have rifles with both. Most modern scopes have significantly more adjustment than needed for most shooters, 25-35 mils (2000+ yards for most modern magnums) depending on the scope - plenty no matter which rail you choose. Pick one and go.

 

[wilehunting]

Fellas, I think he's just being deliberately obtuse now.

No, not really.
I was merely responding to huntsman22. He hurt my feelings with the jabbering comment and I was responding to his post. I am learning information from some of the responses.

 

[bluedog69]

At home I have a Federal Ammunition guide. It has maximum point blank range for their ammo.
A scope WILL increase your 3" high to 3" low maximum point blank range trajectory over using iron sights.
Taller rings will do the same.

Think of a quarter back. Short pass is a lazaer. Long pass needs to be angled up higher.

20 MOA rail. If your scope has 60 MOA adjustment and it is mounted parallel to the bore you have 30 MOA up and 30 MOA down. Put a 20 MOA rail on and you now have 50 up and 10 down. In a theoretically perfect world.

 

[bluedog69]

More jabbering;

While a 0 Moa rail is the same thickness front to rear it is not parallel to the bore. It is simply mechanically & physically impossible. If your scope is 1.5 inches above the bore and the base is parallel to the bore the bullet would never come into the line of sight. Gravity starts pulling the bullet down at 32 ft/sec squared the instant it leaves

So……when you dial the scope to hit higher it moves the apparent place of the reticle in space. It actually moves the crosshairs lower so that you then POINT the gun higher.
A high end gun is probably closer to parallel to the bore(perfection is un achievable). I have sighted in some super cheap guns that you could tell that the scope rail was sitting crooked as could be on the gun. Think low right in the front and left in the back. Had to move the scope a long ways but it still shot great.

 

[Hugger-4641]

Nothing for me to say that hasn't already been explained, but I'll throw in my 2c with a little different angle anyway:

With muzzle loaders and slower pistol-caliber rifle cartridges, yes, if zeroed at 100yds, the bullet usually has another zero point about 30yds from the muzzle. These are generally low BC and low velocity, usually 1700fps or less. With high velocity rds like my 300wm that's doing 3000fps, the 100yd zero is the first point that the bullet and reticle intersect (zero) and there is another point around 150yds or so that is also zeroed, depending on the cartridge. I usually zero my hunting rifles about 1" to 1-1/2" high at 100yds, so my two zero points are usually around 80yds and 200yds depending on the cartridge.

When zeroed 1" high at 100yds, my 300wm usually needs around 8 moa dialed up for 500yds and around 13moa for 600yds.
The Burris Veracity that I have on my X-bolt 300wm has 64moa of adjustment. That's 64moa of total adjustment, so if the scope was perfectly mounted and already mechanically zeroed at 100yds, I'd have 32moa of adjustment up or 32 moa of adjustment down.
Theoretically that should get me well past 600yds without needing a 20moa rail.

Rarely is a scope perfectly mounted and already mechanically zeroed at 100yds, but generally after centering turrets on this Veracity, I usually have to dial down 6 to 8moa to be zeroed at 100yds. So I'm guessing that I actually have about 40moa of up elevation available on this combo, probably due to a slight misalignment of my rings or base that happens to be in my favor. Your milage my vary, but if your scope has at least 40moa total of adjustment, your turrets are centered, and is not requiring more than a few Moa of up or down adjustment to achieve zero at 100yds, then you should have no need of a 20moa rail until you are well past 500yds with that 30-06. If you are running out of adjustment at 500yds, then instead of getting a 20moa rail, I would figure out what's not right with your base or rings

 

[Troutslayer2]

All good info...my personal thoughts and conclusions were under 500 yards no need for anything other than 0 moa rail. Over 500 it will be a benefit.

My 280 has a flat rail. I can dial way beyond 1000 yds considering how much travel my optic has, so I do not have need for it. For me it's just basic math- how far until my bullet is moving too slow to kill an animal? How many clicks to shoot that far? Does my scope have that many clicks available? The answer for me is yes so I'll take the allegedly better image one is supposed to see when looking straight through the scope rather than through a tilted scope.

 

[Turpentine21]

Just an example of the flight path of a 147 grain bullet from my 6.5-06 with 20moa rail. The scope objective is 56mm plus dust covers so I use high rings that are approximately 2.25 inches above the bore. It's sighted in 1.7 inches high at 100 yards. You can see how the bullet goes thru the LOS at around 30 yards and then drops back thru at (zero) approximately 230 yards. The 20 moa rail simply gives you added adjustment when shooting at longer distances.
In another example a friends 18" 6.5 Grendel shooting 123 eldm's with a 0moa mounting system coupled with his Meopta scope runs out of adjustment at 600 yards. That is the max distance that he can dial and shoot point of aim/point of impact using the center of the crosshair. In order to extend the POA/POI distance he needs a scope with more adjustment or the simpler option is to add a canted rail such as the 20moa rail you mention. Adding that 20moa rail would give him approximately 120 inches more vertical adjustment at 600 yards. There could be an error in all this as I'm in wind down mode now and may or may not have had a beverage or two.
Every scoped rifle I have except for the rimfires has a canted rail.

 

[sp6x6]

hugger your wrong.Look at a ballistic app It crosses first some where around 25 yrds.Many site in procedures use this as a starting point.Been that way for ever.I grew up shooting weatherbys,they shot flat but is the same for all.It doesn't cross first at 100.Look at diagrams already posted