20MOA bases too much?


Well-Known Member
Jun 25, 2003
Aussie in Italy
I have just put in an order for bases, rings and scope for my new rifle, .308win HS Precision HTR.

A friend just warned me that 20MOA bases are used for 100yd shooting and may not let me shoot down to and under 100m.

Is this true?

I am waiting on a quote for the shipping so I could still change the order if need be.
20 moa bases are typically used for shooting 1000yds while keeping the reticle optically centered (or there abouts) in the scope tube.
If you do not intend on shooting very long distances with the .308 than I do not see any advantage to these bases. Most of the tapered bases are fairly tall so they may raise your scope height more than you expect. However, lower rings may work with the taller bases and still give acceptable height.

I have 20 moa bases on rifles that have been shot at 100yds but this is certainly not ideal and may not work with scopes that have minimal verticle adjustment. Not sure on this though.

If you plan on shooting to 1000yds you will need the 20MOA bases. My Rem. PSS 308 has a Badger 20 MOA Rail and I have no problem shooting at 100yds. The Tasco SS 16X has 100 min. of adjustment and I'm 41min. up from the bottom at 100yds. If you only plan to shoot to 600yds I don't think it would be needed but you never know, you might get the itch to shoot farther and then you won't have the adjustment you need.
Most of the shooting I will be doing will be at 300meters at my local range and around 500m at home where I have more space to stretch out.

That said, it It will be some shooting at 100m and when I'm hunting you often get shots a lot different to what you hoped for.

Exactly what inconveniences will 20MOA bases give me if I didn't need them? Will the aiming point be somewhere in the other half of the scope for shooting at 100m? 300m?

The scope is a Nightforce NF 8 - 32 x 56 which has 50MOA of internal adjustment availiable.
The rings and bases are going to be Baer 30mm steel rings and a Baer base.

Otherwise, can someone give me an idea of what sort of base to go with? Considering that for now, most of the shooting will be in the 500m range with shooting at 1000m is something I want to do, I never have done anything at that range yet.

I was hoping to put up a big metal gong and just see if I can hit it...

I have an 8x32 nxs also and it has 65moa adjustment(62moa acutall). If you only have 50 i would tend to think that something is wrong with the scope. I would double check and if you only have 50moa i would call nightforce and talk to them about it.
Ok, sorry if I seem to be a bit slow to understand this...

I just spoke to the helpful woman at Brunoshooters supply about getting me a 1 piece base instead of a 2Pc since that is all they advertise on their site.

She will probably contact Nightforce and get one of their 1Pc bases which are still 20MOA.

To be more direct:

Zeroed at 100m, will the reticle appear to be out of center?

What about a 300m zero and a 500m zero?

Matt: 50MOA of adjustment is what they say the scope should have on the Nightforce site, for an NF series scope, not the NXS.
The reticle will not "appear" out of center, regardless of the base you use. It will always appear to be centered to your eye, even at the end of the adjustments. The problem arises when you either cannot zero because you don't have enough internal adjustment, or you can zero at 100m with your elevation knob, but you cannot zero the windage because the extreme elevation adjustment has used all of your windage adjustment. Imagine a tube inside a tube; this is how the scope erector system works.
The 20 minute rails are used particularily at 1000 yds target shooting so as to raise the cross hairs in elevation AND leave travel in windage for wind comp. The adjustments on most scope are not rectangular. SO at extreme ends of adjustment
up/down, left/right the cross direction is restricted. Therefore it depends on which scope your using. Some Leupolds have +/- 50
minutes travel (takes 308WIN/175 SMK ~34 minutes elv. for 1000yds) A Tasco scope may only have +/- 12&1/2 minutes. so you see the equpiment dependancy. rjb
Not mentioned in above post is that one can use scope rings to compensate or adjust scope
from out side, This saves interal adjustments for wind etc. I believe Harrel
1 piece rails can be had in 15 or 20 minute
angle. The rings mentioned are the Burris
Signature rings with plactic inserts. While
scope tilt can be done with these rings they
also offer an alternative. That is perhaps
if tapped holes in action or barrel intallation adds up off center bullet impact.
The Burris rings can be used to center scope tube in both elevation and windage from outside. May sound like a lot of fussing. Butt consider what we pay for good scope is should be mounted so it can do it's thing.
Note to "see" how close the crosshair image
is off center do this. Take small cardboard box and cut two Vs in oposed sides to support
your scope. Set up a white plane surface lighted in from of scope and then look throught as you slowly rotate the scope. If you desire a true starting point adjust the knobs until the crosshairs do not appear to
wobble as tube is spun. THIS is the scopes
natural Zero. Keep the same knob settings (or on some scope you can readjust the knobs with allen wrench to TRUE zero). To continue the experiment reinstall scope on rifle and
fire a group at large paper at 100 yds. What
all this will show is how much drift is in mounting. Most people pop a scope on a rifle and "go zero it in" that's fine for the deer woods where the caps on the adjustments may never come off again. But for outwest or actual long range hunting they may find the mounts can help with elevation or if scpoe in cockeyed on action most of windage etc. in one direction was used up on "zeroing in". The wind has been known to blow both ways (sometimes at same time at long range) So knowing the exact amount of scope adjustment and how to use chart info might
make your day rjb
Express. I hope this helps.

Your nightforce scope should have about 100 MOA of TOTAL adjustment of elevation so lets use that for this example.

Lets say that you mount your scope with standard rings and bases. Next lets say that you are lucky enough to shoot a group that is right on the bullseye at 100 yards with your elevation knob opticaly centered. That means you can dial your knob down 50 MOA (inches) or up 50 MOA (inches) at 100 yards.

Now you re mount your scope with 20 MOA bases OR rings. Next you adjust your elevation knob to shoot the bullseye at 100 yards again.

You will have 70 MOA of upward adjustment and 30 MOA down adjustment and you can still Zero at 100 yards.

Now lets say you re mount your scope with the night force 40 MOA base and re adjust for 0 at 100 yards.

You will have 90 MOA up and 10 MOA down and still be zeroed at 100 yards.

Also, as mentioned earlier, your sight picture will always look the same.

I was able to shoot to about 850 yards with regular rings and bases out of my .308 and leopold scope adjusted all the way up. Then I had gunsmith darryl holland make a one piece base/ring type of mount with what he thought was the appropriate taper.

I believe it is around 20MOA but I don't know for sure. I do know that with my elevation turned all the way up I can shoot the crosshairs at 1100 yards and still can adjust back to have a 100 yard zero (or less if I want).
4Ken Horn, thanks for your reply.

It doesn't look like I will have any great problems at this point; I don't care for using clicks to make adjustments, rather prefer to use the reticle for reference in holdover and establish where my impact points are along the NP-R2 reticle. At the moment I use a scope with the NP- 1RR and find it to be very good.

The only drawback is that it will only work on pre established settings (from memory at 22x for this particular model)

rjb tells us that he needs apporxamantly 34MOA of adjustment for a 1K zero so it looks like I should have enough room to do so should I desire.
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