So... Help me out with some calculations

[quadmx301]

So I recently bought a Redfield Battlezone 6-18x44mm riflescope for my Remington 700 .308 Project. It's going to be a temporary place holder so I can build it, and eventually replace it with a higher quality optic. I have been doing some research into ballistic calculations and trig functions; it's fascinating. My goal would be to ultimately achieve first shot hits at most ranges up to 700 yards.

That said, my optic only has 36 MOA of adjustments, both vertical and horizontal. I've purchased a Weaver 20 MOA rail for my receiver. This is where my question comes in.

With an average ballistics chart taken into consideration for a 168 grn .308 projectile, Will I have trouble with a 100 or even 200 yard zero with this 20 MOA rail, since I only have 18 MOA adjustability up or down? I don't necessarily want to have my zero on the razor's edge of my scope capabilities. What do you guys forsee being my difficulties in the zeroing process?

Thanks!!

[Merc1138]

I don't see why you'd have any difficulty getting a zero at 100 yards, and the 20 moa base should help to 700. But the biggest problem I see is that scope comes with BDC turrets instead of turrets that actually allow you to dial in the drop. You could count clicks I guess, but that seems like it would get really frustrating really fast.

[quadmx301]

Even with only 18 MOA of movement from center to offset the 20 MOA base? How do you figure? Could someone explain this to me mathematically?

You make a good point about the turrets. I expected to live with it for now, I don't mind counting clicks too much. I may see if someone would be able to repaint them.

[LynnJr]

If your scope when installed in the rings is optically centered and you add a 20 MOA base you WON'T be able to zero at 100 yards.

Your current scope has 18 MOA up and 18 MOA down totaling 36 MOA of travel.

You should be 2 MOA short of your goal but rarely is a scope optically centered so there is a chance it might work.

That said scope tubes are round so if your all the way down on your elevation turret you won't be able to go to the left or right.Picture a golf ball sitting in a bowl with a perfectly round bottom.The golf ball will always seek out the lowest point in the bowl and once there it will need some height to move horizontally.

I would go with Burris rings with the offset bushings or a 15 MOA base.

[quadmx301]

Perfect, that's EXACTLY what I was looking to hear. Thanks!!!

[Merc1138]

Lynn would be correct, I misread that as having 36 moa of travel in either direction.

Personally I'd return that scope and get something else for the turrets as I mentioned earlier, and due to the silly low amount of travel.

[JMP]

As Jr said. However, you may wish to count the clicks as well and see put it on a target and see how much elevation travel you get top to bottom. Sometimes scope makers publish the total elevation travel conservatively and you wind up with more. That, plus where it is centered, might work.

I use a 1/3 cant as a rule of thumb as you generally get about half up/half down with some difference due to the scope's center and the fact that your scope sits above the rifle. This gives you some slack at the extrema for horizontal adjustment.

That said, I'd get a 0 MOA base with offset inserts or a shim in your rings to give you a little boost. If you have a 24"+ barrel, you don't need a whole lot of elevation for 700 yards in .308 Win. It's after that distance that it starts falling off a cliff. You should be able to make 600 yards with no cant.

The reason I'd go with the 0 MOA base is that you can later get a cant built into a mount of your choosing. I much prefer mounts to rings, but that is just me. That way you have the right cant for your scope, and it's easy to move from one rail to another without much fuss.

[ar15barrels]

So I recently bought a Redfield Battlezone 6-18x44mm riflescope for my Remington 700 .308 Project. It's going to be a temporary place holder so I can build it, and eventually replace it with a higher quality optic. I have been doing some research into ballistic calculations and trig functions; it's fascinating. My goal would be to ultimately achieve first shot hits at most ranges up to 700 yards.

That said, my optic only has 36 MOA of adjustments, both vertical and horizontal. I've purchased a Weaver 20 MOA rail for my receiver. This is where my question comes in.

With an average ballistics chart taken into consideration for a 168 grn .308 projectile, Will I have trouble with a 100 or even 200 yard zero with this 20 MOA rail, since I only have 18 MOA adjustability up or down? I don't necessarily want to have my zero on the razor's edge of my scope capabilities. What do you guys forsee being my difficulties in the zeroing process?

Thanks!!

Figure on it taking 5 moa just to get zeroed at 100yds.
Starting with 18moa up and 18moa down, switch that to 13moa up and 23moa down.
Now put on a 20moa base and you have 33moa up and 3 moa down.
That is MIGHTY close to not working for a 100yd zero.
Some scopes will have more or less travel than advertised so you would need to spin your scope in to mechanical zero and then check it's travel.
You would be MUCH safer with a 10moa or 15moa rail.

[JMP]

Figure on it taking 5 moa just to get zeroed at 100yds.
Starting with 18moa up and 18moa down, switch that to 13moa up and 23moa down.
Now put on a 20moa base and you have 33moa up and 3 moa down.
That is MIGHTY close to not working for a 100yd zero.
Some scopes will have more or less travel than advertised so you would need to spin your scope in to mechanical zero and then check it's travel.
You would be MUCH safer with a 10moa or 15moa rail.

That's a conservative estimate for figuring total elevation up. But, now it's the opposite situation where we he wants maximum elevation DOWN to fit a 20 MOA base. So, I'd ignore it to be safe, but you may be on to something.

Perhaps with 10" high rings, it could work since you'll need to dial down about an extra MOA per inch your scope sits above the barrel.

Mount some tall rings on top of 3 sets of these mounted on top of eachother:


I would never do this, but in the spirit of considering all possibilities, I present this ridiculous solution.

[ar15barrels]

That's a conservative estimate for figuring total elevation up.

It takes about 5moa of angular correction to account for the difference between bore axis and the scope axis as well as to get the bullet above the line of sight so that it passes back through the line of sight at 100yds.

It's slightly different based on scope height, but what matters much more is the velocity/bc of the bullet.

[JMP]

It takes about 5moa of angular correction to account for the difference between bore axis and the scope axis as well as to get the bullet above the line of sight so that it passes back through the line of sight at 100yds.

It's slightly different based on scope height, but what matters much more is the velocity/bc of the bullet.

No argument from me on this fact; however, I'd ignore this to be conservative as I have found that the center of scopes tend to err on the low side since folks generally want adjustment up. In this case we want more adjustment down to accommodate a 20 MOA base. I'd wager that it does not zero at 100 with a 20 MOA base, could go either way.

[ar15barrels]

No argument from me on this fact; however, I'd ignore this to be conservative as I have found that the center of scopes tend to err on the low side since folks generally want adjustment up. In this case we want more adjustment down to accommodate a 20 MOA base. I'd wager that it does not zero at 100 with a 20 MOA base, could go either way.

So we are using the same terms... UP elevation (to you) means scope elevator travel DOWN and resulting bullet travel UP right?

That being the case, a 20moa canted mount eats up elevation DOWN travel.
But, the 36moa scope case is interesting BECAUSE of the 5 moa UP elevation lost to the zeroing, also puts the gun about able to absorb 20moa of rail cant.

[russ69]

Try the 20MOA base and see if it works. If it does, you'll have a good amount of elevation to get you way out there. Otherwise do as AR15barrels says and get a 15MOA base.

[CRTguns]

the better route would have been burris signature rings with posi-line inserts. you can adjust the to get any odd amount of incline you want. Id use them all the time in my shop. run the scope down to its "bottom", turne it up about 10 clicks, then set it on the rings while viewing a columnator boresight. swap posilign inserts till the x hair is centered on the columnator. done.

20 moa was an arbitrary figure chosen beacuse it can be represented by a .025" rise over a 5" run. easy to program. it's a third of a degree.

Farrel does make bases in 5, 10, 20 and 30 moa iirc.

[ar15barrels]

20 moa was an arbitrary figure chosen beacuse it can be represented by a .50" rise over a 5" run. easy to program. it's a third of a degree.

Methinks there are some zeros missing here.