# 20 MOA Scope Base?



## Wolf6151 (Jun 13, 2005)

At what point in shooting long distances does it become necessary to use a 20 moa scope base?


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## Ernest (May 21, 2004)

At the point that you run out of clicks up on your scope. 

So, what scope, what caliber, and what load? Low BC and/or slow bullets require a base at a shorter distance relative to high BC and/or fast bullets.


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## fishfeeder (Jan 29, 2009)

I am encountering the same issue. .308 with a Nightforce NXS 8-32X56. Gonna try the 168 SMK. I just read on a forum(?reliable) that the .308 has 26" of drop at 1000yd. I believe the NXS has +/_ 56" of MOA adjustment. I am feeling I might need to stick with a flat base. Help is appreciated...


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## THE JAMMER (Aug 1, 2005)

fishfeeder said:


> I am encountering the same issue. .308 with a Nightforce NXS 8-32X56. Gonna try the 168 SMK. I just read on a forum(?reliable) that the .308 has 26" of drop at 1000yd. I believe the NXS has +/_ 56" of MOA adjustment. I am feeling I might need to stick with a flat base. Help is appreciated...


Lots of factors will affect what you're talking about. If you're shooting a 168 smk 308 (bc .447) at 2625 fps, and your gun is sighted in dead on at 100 yds, and your scope is 1.75" above your bore, 500' altitude, 60 degrees temp, believe it or not, that bullet will drop about 436" at 1000 yards requiring over 40 moa up correction to make the shot. So if your scope has 56, you should be good to go.

At that range it will have 474 ft pounds of energy- about the same as the muzzle energy of a 357 magnum shooting a 140 gr bullet at 1250 fps muzzle. So will a 308 kill at 1000 yards? Would you want to have a 357 magnum shot into your chest at 1 yard???

Check out this great web site www.biggameinfo.com It has a great ballistics calculator on it.

THE JAMMER


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## RJustice (May 28, 2008)

I am in the market for a base myself. I ran out of clicks just over 300 with my scope. 

Jammer

I think your math is flawed.

If you need 40 moa adjustment for 1000 and your scope only has 56, then it all depends on where the scope is at 100. The 56 moa adjustment for the scope is from top to bottom or right to left. The scope might be somewhere close to the middle of the range of adjustment for your 100 yard zero. This would give you less than 56 moa of adjustment.


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## Ernest (May 21, 2004)

Many of the nighforce models have 110 MOA of total adjustment. Hence the reference to +/- 56 MOA. Thats 56 up and 56 down. Round numbers. 

If you run out of clicks at 300 with a decent weapon and scope, something is very wrong. 

Thats less than 3 MOA of verticle on Jammer's hypothetical SMK 168's from a 200 yard zero and a 1.5 scope height. (2.84 under local conditions for me).


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## fishfeeder (Jan 29, 2009)

Ernest said:


> Many of the nighforce models have 110 MOA of total adjustment. Hence the reference to +/- 56 MOA. Thats 56 up and 56 down. Round numbers.
> 
> If you run out of clicks at 300 with a decent weapon and scope, something is very wrong.
> 
> Thats less than 3 MOA of verticle on Jammer's hypothetical SMK 168's from a 200 yard zero and a 1.5 scope height. (2.84 under local conditions for me).


Hence my question on the bases. I realize that it has some contingency on bullet size, velocity. etc., etc.. But starting off i don't know where I will end up with this gun so with your experience, would you set it up with a flat or canted base? Seems to me that with that much adjustment available on the NXS, a canted base PROBABLY wouldn't be necessary. Is my thinking twisted?


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## fishfeeder (Jan 29, 2009)

THE JAMMER said:


> Lots of factors will affect what you're talking about. If you're shooting a 168 smk 308 (bc .447) at 2625 fps, and your gun is sighted in dead on at 100 yds, and your scope is 1.75" above your bore, 500' altitude, 60 degrees temp, believe it or not, that bullet will drop about 436" at 1000 yards requiring over 40 moa up correction to make the shot. So if your scope has 56, you should be good to go.
> 
> At that range it will have 474 ft pounds of energy- about the same as the muzzle energy of a 357 magnum shooting a 140 gr bullet at 1250 fps muzzle. So will a 308 kill at 1000 yards? Would you want to have a 357 magnum shot into your chest at 1 yard???
> 
> ...


I wasn't questioning if it would kill at 1K yds., Jammer. I'm sure it would. At least hoping so..... Heck the only reason I bought it was because a "buddy" of mine put a bug in my head reminding me that the 22-250 I just bought didn't have the umph to kill anything at longer distances...that is, IF I decide to kill something besides paper:biggrin:

I am just easing into the longer range shooting and your figure of 436" drop reminds me that I will be spending ALOT of time on the shorter ranges "tuning" it...


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## Ernest (May 21, 2004)

If you have 110 total adjustment, I would think you are unlikely to need the bases.

But, you have a killer scope. A Luppy 6.5x20x40 has only something like 90. A luppy 4.5x14x40 has only 70 or so. Luppy 10x has something like 75.

600 yards with Jammer's example and a 100 yard zero is only 16 MOA (give or take).

Now, Jammer's example involved a high BC bullet (relatively speaking, everything else being equal) shot at a medium velocity. Change the BC down, and the drop increases. BC is an investment all the way to the target. It never stops helping you. Velocity bleeds down quick.

So, take away message, if you did not have such a rockin scope OR you wanted to shoot low BC rounds, you may need the 20 MOA bases in .308. For 99.9% of shooters, they don't need the bases. If the scope can't click up 16 MOA, its a POS for shooting 600 yards.


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## JuanGrande (May 29, 2010)

Go with the canted base for your .308. You can't go wrong. A flat base MAY limit your long range potential, a canted base WILL NOT. I'd suggest you set your rifle up for a 600 yard zero if you really are getting serious about long range shooting. While a 100 or 200 yard zero is fine for hunting, it's a lot of clicks to move to 1000. 

I shoot .308 with a 20 MOA canted Badger Ordnance base and rings. Current set up is with a Leupold Mk IV M3. This scope has 1 MOA adjustments for elevation and is super slick. This means I have 4x less "clicks" than you do and makes corrections for distance that much quicker. 

Be sure to mount your scope as close to bore line as possible, at long ranges it makes a difference.

Just my $.02


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## THE JAMMER (Aug 1, 2005)

RJustice said:


> I am in the market for a base myself. I ran out of clicks just over 300 with my scope.
> 
> Jammer
> 
> ...


R,
I'm sure you've read Ernest's two responses to this.

Also for all I was just throwing in the kill info. Two weeks ago I had heard that statement made by an army sniper on a tv show, so while I was in the program, I just plugged in the numbers to see if he was correct, and he was.

THE JAMMER


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## RJustice (May 28, 2008)

Did not know it was 56 up and 56 down. Total 112. A lot of useful information.


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## THE JAMMER (Aug 1, 2005)

Rjustice,

That's great. I'm just really starting to do some of this long long distance shooting, and may find myself in the market for a base as well.


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