I've had, let's just say, a project in mind for a year. I needed to know how much canted base was going to be needed to reach my goal, based on what the scope has available.

The scope has a reported 35.0 Mil of travel. And I could potentially need +/- 30.0 Mil to get where I want to be. Picatinny rails are in graduations of MOA, but I use Mil. So here's how it works. You'be got to convert the extra MOA the base is giving you to how many Mils it is going to give you.

MOA divided by 3.43 = Mil

On a 0 MOA base, in theory, I will have half the travel available, so 17.5 Mil. And down travel is absolutely useless.

20 MOA = 5.8 Mil
30 MOA = 8.7 Mil
40 MOA = 11.6 Mil
50 MOA = 14.5 Mil
60 MOA = 17.5 Mil

^^Those Mil values are what is added to the halfway point of the scope travel. Remember on a 0 MOA base the scope should have 17.5 Mil up travel available. So I can add those values to the midpoint of 17.5

20 MOA base gives a total of 23.3 Mil
30 MOA base gives a total of 26.3 Mil
40 MOA base gives a total of 29.1 Mil
50 MOA base gives a total of 32.0 Mil
60 MOA base gives a total of 35.0 Mil

The danger zone of using a very canted base is you could have the elevation turret bottomed out, and you're impacting high at 100 yards, but there is nothing you can do about it. You have to decide, for the project if that is acceptable or not. Or is running out of up travel more acceptable.

I thought this information might help guys understand the reason for canted bases. And by the way, that means they raise the rear of the scope, which tilts down the front of the scope.

(Don't ask what the project is, because I won't tell)

Additionally, while you may top your scope out, you still have the reticle to use for the remaining hold values.

Also to add on to this, I don't recommend going less than 10 moa (or 3 mils) on the bottom end of scope travel. You can calculate the math figures exactly, but the mating up to the base of the action, canted base, rings, and scope often have some manufacturing error factor in one or more of the items. The 10 moa/3 mil cushion is the minimum, or closest I would go to give you some breathing room. I've seen on several high end scopes where shooters purchase a 20 moa base, but the amount of internal travel in the scope won't allow a 100 yard zero because the scope didn't enough internal adjustment, plus the error factor of the base of the action, canted base, and rings.

Yes, yes.

I'd rather not have to add a hold here, but that is an option. I've had to do it before.

What Skylar us saying is when your reticle matches your turret. Say you need 20.0 Mils of elevation, and you try to dial your turret to 20.0 elevation correction. As you dial, the turret stops at 16.0 Mils. To keep from damaging the scope dial it back some. In my opinion I'd back out 1.0 Mil to keep round numbers. So now we've dialed up to 15.0 but need 20.0, we ran out of travel. OK hold 5.0 in the reticle. Because 15.0 dialed, plus 5.0 held equals 20.0 total. Same, same.

Right, Chad.

That's why I mentioned to keep in mind this could happen, and which "potential" problem is more acceptable to the individual.

Very helpful for a project I'm building as well. Thank you for the cliff notes.

Yessir. Glad it helped someone.

I bet that project is a big one. Something like a Norma.

Zero at 200-400

If you aregoing for long distance why zero at 100?

I bet JG is trying to take a 22lr out to 800 yds.

Don't put it past me.

Wish I would have thought of that.



Same reason I always do, perfect zero, with no wind error. Might not be possible with this rig, though.

Just ran into this with a 260 stalking project built off a savage. Tried running the scope on the 20moa and scope doesn't work with that base for its intended purpose. Very helpful post FJG

So if I'm trying to push a 20" .308 with 155 AMAX to 1000 yds, do I need a canted base? I have a 0 and a 20 and can use either one. Scope is a Bushy 6245FJ

Specifications for Bushnell Elite Tactical 6-24x50mm Fully Multi-Coated Rifle Scope:
Finish: Matte Black
Magnification: 6x to 24x
Objective Lens Diameter: 50mm
Tube Diameter: 30mm
Field of View (at 100 yards): 6x - 17.5'; 24x - 4.5'
Weight: 27 oz
Length: 13.5"
Eye Relief: 4"
Exit Pupil: 6x- 7.5mm; 24x - 2.1mm
Adjustment Click Rate: 0.1 mil
Total Adjustment Range: 24 mils
Mounting Length: 5.9"
Lens Coatings: RainGuard HD, fully multi-coated

Looks like 12 Mils max, so figure 9-10 to leave a cushion? I guess it may depend on what it uses to sight it in at 100. Bulletdrop says for 2" sight height, 155gr at .435 BC and 2750fps, 10.2 mils to reach 1000 yds. I don't know that we'll see 2750 or not. I'll chrono it when I'm done.

I'd mount it on a 20 MOA.

You've got (in theory) 12 Mils up travel available on a 0 MOA base. Mounting on a 20 MOA base gives you another 5.8 Mils of travel, 17.8 total. Again, these are about what should happen. I'd rather have a little extra on the top end.

You're pushing a decent, not great BC, and out of I dare say, only 20" barrel. You might get into the 11-12 Mil correction area, depending on your load MV, and the environmental conditions when you're shooting.

There are hundreds of scopes specifically designed to zero out, at 100 yards, mounted on a 20 MOA base.

12' hold over @ 300 yards .22lr 40gr, @1000fps

this is easy, why do ya'll make me want to take a Tylenol with all your fig's???

We had a CZ 22LR suppressed bolt gun out to 400 the other day. The scope had everything dialed and we were holding with the reticle to get to 400. Anything past that I'm impressed!

I think the objective bell of the scope would be pointing down at the muzzle to get enough come ups...

That's why they make tall, and extra tall rings. And adjustable cheek stocks, and stock packs.