Rifle Scopes 100 MOA/29.1 Mils of elevation travel with 20.6MOA/6 Mil cant/tilt

[bluto77]

Scope has 29.1 Mils of total elevation adjustment available, then the mechanical center of the elevation range will be at 14.55 Mils. Assume when zeroing the scope at 100 yards, you're dead on at the mechanical center of the elevation range. When using a scope mount that has 0 tilt/cant built in to it, the turret will be on "0". That sounds right to me.

If the mount has 6 Mils built in tilt/cant, based on the assumption above, where does that put the turret when zeroed at 100 yards? Is it simply at -6 Mil? And you would then have 20.55 Mils of upward travel and 8.55 Mils of downward travel available?

Seems pretty straightforward, and I feel like I'm asking a stupid question. Just looking for confirmation.

 

[bluto77]

Damn...35 views and no response. I guess it was a dumber question than I thought?!?!

 

[RyeDaddy]

Your thinking is correct. With the above scenario your turret would show 6 mils "down" to hit a target at 100 yards.

You would likely zero at 100 yards, and your turrets would then show 0 at 100 yards and you would have 20.55 mils of "up" elevation available from there.

 

[BobinNC]

Scope has 29.1 Mils of total elevation adjustment available, then the mechanical center of the elevation range will be at 14.55 Mils. Assume when zeroing the scope at 100 yards, you're dead on at the mechanical center of the elevation range. When using a scope mount that has 0 tilt/cant built in to it, the turret will be on "0". That sounds right to me.

If the mount has 6 Mils built in tilt/cant, based on the assumption above, where does that put the turret when zeroed at 100 yards? Is it simply at -6 Mil? And you would then have 20.55 Mils of upward travel and 8.55 Mils of downward travel available?

Seems pretty straightforward, and I feel like I'm asking a stupid question. Just looking for confirmation.

It all may sound "right" to you, but perhaps "your" assumptions are not grounded in reality. Let's assume you first find the mechanical center of your scope, unmounted. Then you mount it on your base and in your rings. The scope is still "mechanically" centered, but it is some distance above your bore, and it may also be right or left of it, because your platform, made up of rifle, base, rings, and scope are not perfectly level and parallel with each other.

The act of zeroing your rifle @ 100 yds will ALWAYS use some amount of elevation up or down and windage right or left. Now the scope is no longer mechanically centered, but it is ZEROED for that rifle, at that range, with that load.

Same goes for a canted base. Yes, it borrows from the down elevation and adds to the up elevation, but how much it adds or subtracts depends on more factors than a simple math problem. Again nothing is really level and parallel, as manufacturing tolerances of all the elements, rifle, base and rings come into play.

So again in theory both your statements above are somewhat correct, but reality does not always cooperate as neatly.....

 

[bluto77]

It all may sound "right" to you, but perhaps "your" assumptions are not grounded in reality. Let's assume you first find the mechanical center of your scope, unmounted. Then you mount it on your base and in your rings. The scope is still "mechanically" centered, but it is some distance above your bore, and it may also be right or left of it, because your platform, made up of rifle, base, rings, and scope are not perfectly level and parallel with each other.

The act of zeroing your rifle @ 100 yds will ALWAYS use some amount of elevation up or down and windage right or left. Now the scope is no longer mechanically centered, but it is ZEROED for that rifle, at that range, with that load.

Same goes for a canted base. Yes, it borrows from the down elevation and adds to the up elevation, but how much it adds or subtracts depends on more factors than a simple math problem. Again nothing is really level and parallel, as manufacturing tolerances of all the elements, rifle, base and rings come into play.

So again in theory both your statements above are somewhat correct, but reality does not always cooperate as neatly.....

This response is more along the lines of what I was looking for. I do know that the scope will not be at it's mechanical center whenever it is mounted and zeroed at 100 yards, I was just using that assumption for simplicity to talk about the what effect the degree of tilt built into the mount would have on my elevation adjustment range. First, I wasn't sure if it was based on the simple calculation of just lowering the starting point when zeroed by 6 Mils, assuming everything is perfectly sqaure/parrallel/etc. Once I knew that, then I wanted to know what different factors could cause that that number to be different than the amount of built in cant, and how they would effect it.

The bottom line being I am trying to figure out if there is any real downside to having a canted mount when you really don't need it. In my case, I'm putting a US Optics SR-8 in a Spuhr SP-3616 mounted on a 300 BLK flat-top AR-15. As previously stated, the scope has 29.1 Mils of total elevation travel and the mount has 6 Mil cant built into it. My original thinking was there was absolutely no need for a mount with any built in cant/tilt because the 300 BLK cartridge won't be shot out past 300 yards on game, and not a whole lot further when punching paper. The only reason I'm getting the mount with built in cant was because I'm getting a great deal on a used unit. I was considering not getting it though because of the built in cant. And I wouldn't have if the scope didn't have so much elevation travel available, otherwise I could find myself at the very bottom on the elevation adjustment range for my 100 yard zero, or worse yet, not be able to get a 100 yard zero, which wouldn't make sense for a rifle that will be used to shoot stuff found primarily in the 75 to 150 yard range. However, given the wide range of elevation travel, I should have a sufficient "cushion" below my 100 yard zero point. Now it's starting to actually look like a better idea to have the 6 mils built in cant because of the 300 BLK ballistics. I'll be shooting all supersonic ammo, but it still starts dropping decently fast after 200 yards, and really fast after 300, so it will be nice to have the extra adjustment range so I can dial in (my preference) instead of holding over out to the 400'ish range.

And for what it's worth, when I zeroed this scope at 100 yards with the Badger mount it's sitting in, it was only .2 Mil higher than the mechanical zero. Never had one that close to true mechanical zero.