Decided to turn my spare lower into an SPR setup. I’m currently thinking my optic of choice will be PA Glx 3-18 griffin mil. My rationale is that this is primarily going to be a range toy and weight isn’t an issue (wish I had somewhere to go trek around the wilderness with my SPR ??). If my crypto “investments” exceed my expectations then I might go with the ATACR 4-16. With that in mind is there any downside to using a scope mount with 20 MOA cant? Would one ever need that for 5.56? I figure if I really get into the long range stuff I can move that scope to a different caliber and get a proper 2.5-10 SPR style scope for this rig.

I provide all that unnecessary info so you can feel free to criticize my rationale for going with the higher magnification if you want but mainly I’m curious if I should get the canted mount or not. Thanks!

It’s largely going to depend on the gun and ammo but for the most part, no, you aren’t going to need it with a 5.56 gun and those optics unless you’re trying to shoot stupidly long distance.  Like, well outside the effective range of the gun/cartridge.

It kinda depends on how far you want to shoot and the magnification of the scope.  I'd say anything up to a 5-25x you won't need any cant.  But if you have something that is in the 40-50x (top end), more than likely you will need it due to limited elevation.

Being you will never make use of all the downward adjustment the scope has, there is really no downside.

WOA says their 20 moa scope mount is used from 600 to 1000 yards.

Paladin

The two most important questions that will help determine if you need the additional elevation will be:

1) What is the range of elevation adjustment for the scope that you plan on using?
2) How much elevation will you need to shoot at your intended distances?

I personally only use mounts with cant for rifles that I plan on dialing >10 MOA on a regular basis, but a 0 MOA mount would serve me equally as well.

Dialed for a center hold.

For some scopes, the best clarity is in the middle of the elevation adjustment.

Will you dial vs hold for elevation and be in the middle of the adjustment range more often than not? If so, get a 20 MOA mount. If not, don't get a canted mount. But consider this...

You will use about 2.5 MOA just to zero the scope. You will use at most a bit over 4 MOA at 300y and around 16 MOA at 600 yards with a 100 yard zero.

So a 20 MOA will be ideal for 600y and up. A 10 MOA mount will be ideal for 300y and up.

You will be getting close to 30 MOA at 800.

A long range 30mm tubed scope of 5-25×50 will probably have a bit over 30 MOA of adjustment in each direction. A 34mm tube will eliminate the NEED for a canted base because of the extra elevation travel.

You WILL NEED the canted base for shooting past 800y with a .223 rifle and 30mm tube. Though, the ability of a .223 to shoot past 800y is dubious because it will become subsonic and suffer transonic accuracy issues.

For .223 I would get 0 MOA or 10 MOA of cant.

What he said, with the additional caveat that some scopes (cough, cough some Vortexes) have extremely limited elevation adjustability, and they bottom (or top depending on how you look at it) and will require a canted mount.  Some of my friends bought the Tikka T3 TACA1/Vortex/Badger package and then were very surprised when they couldn't dial to 1,000 yards with the non-canted mount.  They ended up needing 30 MOA just to dial to 1250.  

ETA: redacted

DevL covered it much better than what I could get through my drug addled fingers.

Excellent info! Thanks everybody!