How to tell you have a 20 MOA base?

[Texas10]

Just got done reading a loooooong thread on zeroing a Vortex here on the optics board, and am now so confused that I'm afraid I may have brained my damage.

So maybe a quick question or two for you "sharp" shooters (see what I did there…?) will help me get the concept of MOA bases.

When I purchased my model 12 BVSS in 223 new, the shop owner installed a set of leupold bases and the scope I'd purchased separately.

Every scope (6 now) I've put in those rings and bases has been very near bottomed out on the elevation turret when zero'd at 100 yds.

Not so with my new 12FV. I installed new rings and bases for that rifle and it's near middle of the MOA capacity at 100 yd zero. Same with my shooting buddy who purchased the same Vortex Viper HS 6-24x50. Went to the 1000 yd range this week and he didn't have enough MOA to hit 500 yds where as I was only in the middle of my turrets capacity at 750. (He's shooting a 308)


As I'm typing this, it seems pretty clear that I do have a 20 moa base. If so, how would I tell?

[short round]

They are thicker on back of receiver, than the front. Really not needed till 600 yds. Your buddies may be on backwards if shooting low, should be able to hit at 500 yds. with standard base.

[Texas10]

Buddy's is an AR10 with mount machined into upper. Needed 27 moa UP to zero at 100. Tried switching rings around. No difference.

[rovert]

On a round receiver it should be pretty obvious it is pitched (as opposed to 0 MOA) just by looking at it. On (rear) flat receiver it is a little harder to see. To confirm that it is actually 20 MOA, your going to want some calipers and a calculator. I did a little quick math and it looks like 20 MOA would be .0349" rise over a 6" run. That was very quickly done though so run the numbers yourself.

[rovert]

Buddy's is an AR10 with mount machined into upper. Needed 27 moa UP to zero at 100. Tried switching rings around. No difference.

There are offset AR mounts with 20 minutes correction built it. If he is using reg rings on the picatinny rather than an offset, Burris Signature rings should do what he needs to do. They make a tactical style Signature as well as the Zee rings.

[Russmerle]

If there is difference in height with the rear of base vs front, it is probably 20MOA. Mine is noticeably different. There are also 30MOA bases too but you could just measure from the seem where base meets action to the picatiny wings. Probably the easiest way to tell without removing base...

[m12lrs]

Just got done reading a loooooong thread on zeroing a Vortex here on the optics board, and am now so confused that I'm afraid I may have brained my damage.

So maybe a quick question or two for you "sharp" shooters (see what I did there…?) will help me get the concept of MOA bases.

When I purchased my model 12 BVSS in 223 new, the shop owner installed a set of leupold bases and the scope I'd purchased separately.

Every scope (6 now) I've put in those rings and bases has been very near bottomed out on the elevation turret when zero'd at 100 yds.

Not so with my new 12FV. I installed new rings and bases for that rifle and it's near middle of the MOA capacity at 100 yd zero. Same with my shooting buddy who purchased the same Vortex Viper HS 6-24x50. Went to the 1000 yd range this week and he didn't have enough MOA to hit 500 yds where as I was only in the middle of my turrets capacity at 750. (He's shooting a 308)


As I'm typing this, it seems pretty clear that I do have a 20 moa base. If so, how would I tell?


simplest way is to dial your scope to its limits both up and down and compare it to your 100 yrd zero. now don't lose your 100 yrd zero doing this exercise.

Example: your scope literature says your scope has 60 moa of elevation adjustment. That should be about 30 up and 30 down with a 0 moa base. With a 20 moa base you would only have about 10 down and 50 up. Now these numbers are not cast in stone. Don't be surprised if your 60 moa scope only has 55 moa of elevation or something else. If you have a zero stop set for your 100 yard zero just check how much elevation you have up and compare that to your scopes total elevation adjustment.

easiest way for me to tell. Only takes a minute.

[Russmerle]

Ok so I lied... It's probably not noticeable to the eye. My math goes like this 1 MOA at 100 yards is 1.04"... So 1.04/3600 (3600"=100yds) is .00029"/1" elivation or .00174"/6". I don't think I can see that with my naky eye... Is my math wrong?

[rovert]

Ok so I lied... It's probably not noticeable to the eye. My math goes like this 1 MOA at 100 yards is 1.04"... So 1.04/3600 (3600"=100yds) is .00029"/1" elivation or .00174"/6". I don't think I can see that with my naky eye... Is my math wrong?

Only in that you forgot to take your number (1 MOA) and multiply it by 20 to get .0349 for 20 MOA. Your eye can see that. 1 MOA would be tough.

[Russmerle]

Only in that you forgot to take your number (1 MOA) and multiply it by 20 to get .0349 for 20 MOA. Your eye can see that. 1 MOA would be tough.

Thanks you're right... So it's not in my head that I can see a difference lol

[pitsnipe]

Just got done reading a loooooong thread on zeroing a Vortex here on the optics board, and am now so confused that I'm afraid I may have brained my damage.

So maybe a quick question or two for you "sharp" shooters (see what I did there…?) will help me get the concept of MOA bases.

When I purchased my model 12 BVSS in 223 new, the shop owner installed a set of leupold bases and the scope I'd purchased separately.

Every scope (6 now) I've put in those rings and bases has been very near bottomed out on the elevation turret when zero'd at 100 yds.

Not so with my new 12FV. I installed new rings and bases for that rifle and it's near middle of the MOA capacity at 100 yd zero. Same with my shooting buddy who purchased the same Vortex Viper HS 6-24x50. Went to the 1000 yd range this week and he didn't have enough MOA to hit 500 yds where as I was only in the middle of my turrets capacity at 750. (He's shooting a 308)


As I'm typing this, it seems pretty clear that I do have a 20 moa base. If so, how would I tell?


Texas10


Do I understand that your base is in two pieces? Each attached to the receiver with two screws in front of and behind the feed/ejection port? I've not heard of two piece bases other than 0 moa= flat. You might have flat bases? And those would likely need to be shimmed or bedded to align with each other (as could account for the needed scope adjustment) as Savage receivers are known to need this. My Mdl 10 receiver is .007" higher in the front. So I had to shim the back of the 20 moa base mounted on it. BTW, you can see the 20 minutes of cant in a one piece base.


Snipe

[Texas10]

Yes, I have Leupold 2 piece bases. Looks like this http://www.opticsplanet.com/leupold-standard-2pc-2-piece-base.html

But, I can't find any reference to a 20 moa base in this style from Leupold either. Which leaves me confused.

[m12lrs]

Yes, I have Leupold 2 piece bases. Looks like this http://www.opticsplanet.com/leupold-standard-2pc-2-piece-base.html

But, I can't find any reference to a 20 moa base in this style from Leupold either. Which leaves me confused.

simple way to tell. try this!

simplest way is to dial your scope to its limits both up and down and compare it to your 100 yrd zero. now don't lose your 100 yrd zero doing this exercise.

Example: your scope literature says your scope has 60 moa of elevation adjustment. That should be about 30 up and 30 down with a 0 moa base. With a 20 moa base you would only have about 10 down and 50 up. Now these numbers are not cast in stone. Don't be surprised if your 60 moa scope only has 55 moa of elevation or something else. If you have a zero stop set for your 100 yard zero just check how much elevation you have up and compare that to your scopes total elevation adjustment.

easiest way for me to tell. Only takes a minute.

[Texas10]

Sorry, I guess I left that little detail out. The turret on this scope is 12 moa per rotation, and I am one rotation from bottom at 100 yd zero leaving me about 35 moa available up adjustment, which strikes me as an interesting number since that would work out to be something like a 11 or 12 moa base. Not exactly common.

The rings are Leupold also, 30mm. I bought these recently, and am pretty sure they're STD rings.

Interestingly, the manual included with the scope includes no technicial data whatsoever, but I seem to remember reading somewhere that the scope has 50 moa total. Here's a link. http://www.opticsplanet.com/vortex-viper-hs-6-24x50-riflescope.html?_iv_code=VX-RS-VIPERHSR-VHS-4319A

Assuming the base is a STD base, does it sound to you like the scope might be FUBARd?

[Russmerle]

Sorry, I guess I left that little detail out. The turret on this scope is 12 moa per rotation, and I am one rotation from bottom at 100 yd zero leaving me about 35 moa available up adjustment, which strikes me as an interesting number since that would work out to be something like a 11 or 12 moa base. Not exactly common.

The rings are Leupold also, 30mm. I bought these recently, and am pretty sure they're STD rings.

Interestingly, the manual included with the scope includes no technicial data whatsoever, but I seem to remember reading somewhere that the scope has 50 moa total. Here's a link. http://www.opticsplanet.com/vortex-viper-hs-6-24x50-riflescope.html?_iv_code=VX-RS-VIPERHSR-VHS-4319A

Assuming the base is a STD base, does it sound to you like the scope might be FUBARd?

If she is FUBAR'd I'd say she's FUBAR'd in the right direction ;)

[m12lrs]

Sorry, I guess I left that little detail out. The turret on this scope is 12 moa per rotation, and I am one rotation from bottom at 100 yd zero leaving me about 35 moa available up adjustment, which strikes me as an interesting number since that would work out to be something like a 11 or 12 moa base. Not exactly common.

The rings are Leupold also, 30mm. I bought these recently, and am pretty sure they're STD rings.

Interestingly, the manual included with the scope includes no technicial data whatsoever, but I seem to remember reading somewhere that the scope has 50 moa total. Here's a link. http://www.opticsplanet.com/vortex-viper-hs-6-24x50-riflescope.html?_iv_code=VX-RS-VIPERHSR-VHS-4319A

Assuming the base is a STD base, does it sound to you like the scope might be FUBARd?

I think if you do a little search you will find that most of the so called 20 MOA bases are not really 20 moa. 10 to 15 is most common.

[doctnj]

Sounds like you got confused after reading my thread and I dont blame you. From the outside looking in its pretty clear but once you step off in it it gets cloudy as hell. The canted base is there to shift your cross hairs down in adjustment so you have more up available. If it were exact, it would take 20 from the down and put it into the up available.

When I look at my scope on my remington action (short rail), I can see the cant. When I look at the supposedly 20 moa rail on 110ba rail (long rail), it becomes nearly impossible to see because I loose the reference to the barrel under the continued rail. Since it sounds like you are just using either a two piece or, just 20 moa rings, you should be able to see a cant between the bottom of the scope and the top of the barrel. You could also just slap on a level to the barrel. Get the barrel level then check the level of the scope and it should be going down hill pretty well.

By the way, if you could have read that thread and not walked away with brain damage, it was too late for you anyway. lol

[yobuck]

Wait a minit, wait a minit, your all wrong every one of you. Youve gotta first find which direction is north, meaning (true) north and start from there. lol

[doctnj]

Wow. I never thought about that. Not to mention angle of the sun and it's reflective properties. You know that black is the presence of all colors lol.

[Texas10]

I think you hit it Doc. With the loooooong sun shade on the scope, I can't see any difference in spacing between the barrel and scope, but then the barrel is tapered in exactly the direction that would make it look parallel to the scope IF the scope were canted down slightly.

And as I was setting the scope back in the rings yesterday before going to the range, I noticed that with the top halves of the rings off, when I press on the scope body over the rear ring, the front of the scope rises off the front ring slightly. So the rings are not exactly in line, another sign that I need to get a one piece rail with a 20 moa lift if I'm going to pursue ringing steel at long distances.

Quite a learning process!