Scope rail- how much MOA can I get and still have a 100 yd zero?

[ManOfAction]

The NF NX8 4-32 has 90 MOA of elevation. Divide by two is 45 MOA. So, am I correct in thinking that a 40 MOA rail will theoretically keep my 100 yard zero near the very bottom of the scope's available adjustment? I've heard occasional reports that NF has a small bit more adjustment than advertised, and also that going from a zero MOA rail to a 40 MOA rail does not actually add 40 MOA to your adjustment. If both of those happen to be true, would a 50, or even a 60 MOA rail be better? I want to squeeze every bit of adjustment I can for my 338 Lapua. I'm new to the Hide, so please let me know if this post is in the wrong place.

 

[jasent]

Id go 40. If not enough shim and bed. Has worked well for me

 

[Bandit320]

Do you have the scope? Just dial stop to stop for the exact number.

 

[Bandit320]

You could use the Burris XTR Signature rings with the 40 MOA base time get any elevation you want. They have adjustable inserts for up to an additional 50 MOA.

XTR Signature Rings™ | Burris Optics

www.burrisoptics.com

 

[TripleBull]

I tilt big and hold under if I want to check 100 yard zero.

You might want to pick up the latest G&A Precision Rifle Shooter at your local WalMart and read the interview with Robert Brantley.

I have 20 MOA rail and a 6mil Spuhr mount...

Mixing conventions to make me do math, dammit!

 

[b2lee]

Where are you needing all of this elevation at?....and can I come and shoot there as well?

I have 20 MOA rail and a 6mil Spuhr mount....I wish I would have got the 9mil Spuhr mount...because I still could go up to another 5 mils of elevation to top out the ZCO.

 

[gnochi]

Nightforce is Nightforce, but the best formula I’ve heard that ensures the tolerance stack works with good quality components is:

(Scope elevation - 15moa)/2 = Max advised rail+mount elevation

Using the XTR signature rings you can take it to the limit. THAT SAID, spherical and chromatic aberration tends to be best towards the center of the scope travel and get visibly worse towards the edges, even with alpha glass. If you realistically won’t shoot at distances that you need to zero/100 at the top top of elevation for, don’t do it.

 

[ManOfAction]

I've been using an SWFA 10x with 140 minutes of adjustment to shoot ELR. I'm able to shoot 2,000 yd targets without doing a holdover, but have to hold over for anything past. That is using a 20 MOA base. The 10x is doable for the 3'x3' match targets, but leaves a lot to be desired so I'm considering the NX8. With only 90 MOA of adjustment I'm going to need to compensate somehow. That's a lot of points off my score if I don't have elevation for ~2300 yds.

 

[ManOfAction]

Nightforce is Nightforce, but the best formula I’ve heard that ensures the tolerance stack works with good quality components is:

(Scope elevation - 15moa)/2 = Max advised rail+mount elevation

Using the XTR signature rings you can take it to the limit. THAT SAID, spherical and chromatic aberration tends to be best towards the center of the scope travel and get visibly worse towards the edges, even with alpha glass. If you realistically won’t shoot at distances that you need to zero/100 at the top top of elevation for, don’t do it.

(90-15)/2 = 37.5
So what exactly does this number tell me? Sorry, I don't quite understand the formula.

 

[ManOfAction]

I was told to check out MirageULR. It seems they can make a rail with basically any amount of elevation built in. Or would it be better to go with the Burris rings? Do they hold up well to magnum cartridges? http://www.mirageulr.com/scoperails.html

 

[gnochi]

(90-15)/2 = 37.5
So what exactly does this number tell me? Sorry, I don't quite understand the formula.

It means you’re definitely fine up to 37.5moa rail+mount cant.

You’re most likely good at 40moa too, especially because nightforce tends to give you a bit of extra travel, but if your parts are at tolerance extremes you might have to use a shim.

 

[gnochi]

I was told to check out MirageULR. It seems they can make a rail with basically any amount of elevation built in. Or would it be better to go with the Burris rings? Do they hold up well to magnum cartridges? http://www.mirageulr.com/scoperails.html

If you’re trying to get every last bit of elevation dialing, it’s pointless to order a rail with a specific cant until you know exactly how everything on your rifle aligns.

I probably wouldn’t use the Burris Signature Rings on a 416 Barrett, but that’s less about slippage and more because the scopes that you can fit in rings run out of elevation well before the bullet hits subsonic transition, so a Charlie Tarac or dial-a-slope mount is a more useful solution.

As long as you degrease the scope tube and ring inserts, and use the right torque values, you’ll be fine. If you’re concerned use a bit of hairspray or automotive trim adhesive or rosin, or lightly scuff the insides of the ring inserts with some sandpaper.

 

[slm9s]

Yes XTRs hold up well.

 

[Yerman]

Consider one of these....

ERATAC Adjustable Inclination Mounts

ERATAC - Adjustable Inclination Mounts are in stock, best price, no tax, free shipping - Call (570) 368-3920

www.eurooptic.com

 

[Steel head]

Depends on the scope and and how things line up.
My Cronus zero’d at 100 with a 45moa rail.

 

[gnochi]

Depends on the scope and and how things line up.
My Cronus zero’d at 100 with a 45moa rail.

Yep, (32mrad-15moa)/2 = 47.5moa so that’s expected. I had about that between a 20moa rail and the XTR rings on my Cronus with zero problems.

 

[ManOfAction]

Thanks for all the input. I think Ill take Bandit320s advice and just order the scope, zero it, then count exactly how much I need and then order the rail. Seems like there are a lot of variables and I really need to squeeze every mil I can out of it

 

[Bandit320]

I recently upgraded my scope because the scope I was using had enough elevation for a mile but not much more. I’m not familiar with the scope your looking at. I ended up getting a Vortex Strike Eagle 5-25x56 that has 110 MIA of elevation adjustment and I use it with a 40 MOA rail. It gives me approx. 90 MOA plus the I think 34 more on the reticle. Maybe that would work for you.

Strike Eagle 5-25x56 FFP

Please Select Reticle | 34mm Tube

vortexoptics.com

 

[Fig]

I thought it wasn’t advisable to have your zero at the extreme travel of your erector? @koshkin

 

[koshkin]

I thought it wasn’t advisable to have your zero at the extreme travel of your erector? @koshkin

It is not advisable with most scopes.

ILya

 

[Ledzep]

It's a compromise. Optical quality is not the best at 100yd, but by the time you dial 15 mils (ELR ranges) you're in the center of the erector, and you maintain the ability to adjust the erector to the top of the tube to get as far as possible without a prism or adjustable base.

FWIW I have 40 MOA worth of base/mount in my .300 PRC with a Vortex AMG and think I have like 2-4 mils to spare. FoV/scope shadow looks a little funky until I get past about 500yd, but it's a 37" .300 PRC that I rarely shoot inside of 800yd-- just nice to be able to verify stuff at 100-200yd.

 

[b2lee]

I had max dialed on my Zero Compromise 5-27 MPCT3 this weekend at 2444 yards at TVP. The optical clarity at the top of the range was stunning. 36"x36" target looked much bigger than I would have thought. Did I hit it?....nope!!

 

[Steel head]

My Cronus isn’t all that bad at max elevation.
my old HS-t was noticeably worse.

 

[jasent]

I always zero at the bottom of my elevation. Never had any troubles

 

[ATC4USMC]

Man, glad I ran across this post; got the same scope coming to me soon and had the same question. I found a similar equation that hints at this being acceptable in the scope:
Formula To Calculate Ideal Amount Of Taper/Cant For Your Scope
TEAR = Total Elevation Adjustment Range (Ex. 37.6 mils = 126.9 MOA)

Because the absolute center of a particular scope or where your particular rifle will zero can vary slightly, I’d recommend hedging a bit by doing this calculation based on 95% of your TEAR. (Ex. 126.9 x 0.95 = 120.6 MOA)

ITC = Ideal Total Cant. This is the total amount of cant that would put you very close to the “bottom” of your scope’s elevation adjustment range.

ITC = (TEAR x 0.95) ÷ 2

With this, ITC would be 42.5 MOA. Which is 2.5 under 1/2 of the advertised MOA in this scope. I think this is right....
Im going with a 20 MOA rail and a 20 MOA mount or the Burris sig rings. Interested in what you end up going with and how it works out!!

 

[b2lee]

I always zero at the bottom of my elevation. Never had any troubles

Yep....me too...probably helps that I usually shoot...up 5.5 mils to 15.5mils....so I'm pretty centered...heh

 

[jasent]

Yep....me too...probably helps that I usually shoot...up 5.5 mils to 15.5mils....so I'm pretty centered...heh

One of my rifles is 25” high at 100
Helps that’s exactly the hold under I have in the reticle.

 

[Daherc]

My 338 Edge has a 40 MOA rail and 20 MOA APA BA Mount. My Cronus is sighted at 630 yards and can come down another 3.? mils. The closest I can dial is 275 yards. I have enough dial to get out to about 2400 yards or so before I need to use the reticle.

There is some slight visual distortion at the ends of the turrets as well as the bottom of the lense (bottom of the Christmas tree reticle).

There is not much more out there without going to an adjustable base or a Charlie Tarac. I do not have a need to shoot any closer than 630 yards since my local rifle club has targets out to 1,030 yards, and I can shoot at that line about any day of the week.