Rifle Scopes Is a 20 MOA base really needed with a 34mm scope.

[USW.260]

24" barreled .260rem....34mm scope. Do I really need a 20moa base to get it out to distance. I mean I understand why you would want one. But on something like the Bushnell Ellite, NightForce ACATR or others is it really that big a deal. .260 rem139 senar load off of BulletFlight APP shows only 8.3mils up at my location to get to 1000.

 

[30calDeath]

Dont know if this helps at all but I had a similar question with my Mark6 3-18 34mm and a new scope mount. A guy said it was better to have it and not need it than need it and not have it. So I went with it. Hopefully I made the right decision as I have yet to fully test my new combo.

 

[Rob01]

If you ran the numbers and you don't need it then you don't need it. Simple. But remember you might lose some by having to use windage to zero and also being more centered in the tube will allow you more windage to dial at those longer ranges where it's needed if you dial wind. Using a 20 MOA might not be needed but it also won't hurt anything and they usually cost the same as a 0 MOA base. So maybe the question should be not if you need it but why wouldn't you use it?

 

[Magnumdood]

If you ran the numbers and you don't need it then you don't need it. Simple. But remember you might lose some by having to use windage to zero and also being more centered in the tube will allow you more windage to dial at those longer ranges where it's needed if you dial wind. Using a 20 MOA might not be needed but it also won't hurt anything and they usually cost the same as a 0 MOA base. So maybe the question should be not if you need it but why wouldn't you use it?

Thanks Rob. I was arguing with myself over this very issue. I have a nice (Near Mfg.) canted rail bedded to my rifle that my S&B PM II 5-25x56 is going on. I was considering doing away with the canted rail and putting a 0 cant rail on that rifle. However, your explanation makes perfect sense; I'm going to leave the canted rail on there.

Bay Window Report to follow.

 

[Danco411]

I know I did with my .308 and PST 6-24. The PST only has 65 MOA of internal travel. My dope was 34 MOA to 1000 yards and I only had 27 MOA of travel. I had to hold for the additional 7 MOA. I now have a 20 on it. My 22-250 with 80g Amax's only needed 27 MOA to reach 1K so I was fine. I would think at 8.9 mils you will be fine because most of the 34mm tubes have at least 75 MOA of travel. But like said above there is no reason not to have it.

 

[Graham]

It depends on the scope, not the tube diameter. Some scopes, like the SB 4-16 single turn, are designed to be mounted on an angled base.


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[USW.260]

Well the thought was for that tube dia. with a 0moa base on a Non-Adjustable cheek height stock. Basically trying to keep from building up the cheek weld and still get a centered eye threw scope. Stocks a Manners T5 with a Remington action in .260. So I'll try one of the cheaper 0moa bases out there see how it works. Most likely a Bushnell with Tremor2 rectical. I want to learn to hold off for most if not every shot and dial the longer ones. I also wonder if having a longer Zero say 200 would help.

 

[Rob01]

A 20 MOA base will not raise the scope any noticeable amount over a 0 MOA base. It's so slight of a cant forward. What you need to do is find a lower scope mount and not get one like a Farrell which is known to be very nigh no matter if 20 or 0 MOA.

Stick with a 100 yard zero. You won't save anything with a 200 yard zero and you will have to dial down or hold under for 100 yard shots. With a 100 yard zero everything from 10 feet to 1000+ yards is either dialing up or holding over. Easier to remember.

 

[Gunfighter14e2]

Do I really need a 20moa base to get it out to distance.

Min & max distance & usage?

 

[USW.260]

Min & max distance & usage?

Well it will be my everything rifle. I plan on hunting with it more than anything. Of course I will shoot it as far as I can but I bet it will see way more shots under 600yd than farther.

 

[909er]

I have a Vortex Razor which has a large 35mm main tube for my .308 Semi auto with 22" barrel. There is SOOO much elevation built into the internal elevator due to the maintube diameter that the 20 MOA cant was absolutely not required. The amount of internal elevation that I have available is far more than what my .308 is capable of reaching. Now if you have a .338 Lapua Magnum that you are shooting out to 1500 yards, then you will probably need the scope canted so that you don't run out of elevation adjustment. SOOOO...I say you don't need it.

 

[RonboF117]

Some points to consider when deciding if it would be better to use a canted rail or mount:

1. Does the scope manufacturer comment on it? From S&B's manual - "At the S&B factory the reticles of PM II scopes are adjusted out of center by half the amount of the full elevation range." Decide where you think most of the shots will be taken or the max range for the desired munition, and go from there. If the scope is set up from the factory to be in the range you expect most shots, no need for cant. If not, adjust accordingly.

2. How to decide if you need extra cant? As an example, 20 MOA cant gives you just under 6 mils. Will that work for or against you given the scope you use?

3. If by using cant on the rail or mount, would it keep the erector more in the center? Being a mechanical system, some believe that having the adjustments being closer to the middle of allowable range would provide more "even" tension on the erector and thereby more repeatable performance when making adjustments. The converse being, do you think that having both windage and elevation near or at the maximum of your scope would still provide the best repeatable performance when dialing in that range? Again from the S&B manual: "To get a consistent adjusting range ... the reticle on the scopes is usually set to the optical and mechanical center position."

4. For absolute max range of a weapon system using a PM II scope, I believe S&B recommends 45 MOA of cant. Depending on the ammo used, this should provide for a 100 yard zero and be able to use essentially all of the elevation the scope provides. From the S&B manual - "Mount the scope to the firearm and pre-adjust the scope to a target at 100 m distance using all adjustment facilities the mounts provide so that the least possible amount of elevation range must be used at the scope for fine adjustment."

5. Rule of thumb for deciding the maximum cant. Compute one half the total travel of the system and use that as the maximum cant. For example, the S&B PM II 5-25x has 26 mils of total travel. Therefore, 13 mils is the halfway point. If 1 mil = 3.438 MOA, then 13 mils = 44.7 MOA, and that's why S&B recommends (I believe) a 45 MOA cant.

The above are just some thoughts off the top of my head (and manual) concerning cant on a weapon system. If I am in error on anything I said, please let me know.

 

[George63]

the other consideration that has not been addressed: the quality of the image is best near the mechanical center, that 20 moa slant puts you closer to the center at distance when the best clarity is most needed

 

[RonboF117]

the other consideration that has not been addressed: the quality of the image is best near the mechanical center, that 20 moa slant puts you closer to the center at distance when the best clarity is most needed

George63, that is an excellent point. That last 20% becomes a big deal if you are using hold-overs. That bottom 20% may also be where you end up due to not being able to increase your magnification because the mil point you want would be covered. That just made your 25x a 17x and now you have to ask yourself if you can see the target adequately in order to engage it. And yes, I know people have been killing people at long ranges for many years with a 10x. I'm just expanding a little on George63's comment.