Just asking......

Brutus

Brutus

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So guys, if one had to use a .308 match target rifle, for poking holes into targets at really long range......
is 20 MOA bases enough up MOA for targets up to a mile away?
The scope used will be an NXS 12-42 Nightforce. (30mm)
The barrel is a Krieger, 30 inch pipe, with a 1 in 13 twist.
Ammunition will be 155 Scenars @2850 fps.
(I wonder when my bullets will become subsonic?)

Perhaps this is not viable?

cheers..................:)
 
Your gonna need a base with 20 moa and an adjustable rings (moa adjustable) and probably will end up using some mill dots for more MOA. Some people will say it wont go a mile but it will with the proper set up. That nightforce scope doesnt have allot of moa built in like the 22 power version.

On the extreme side here is what some are using for super long range stuff. You can dial from zero to over 2 miles.
Bruce Artus used this scope set up to shoot a 308 with 240 grainers 3000 yards. He was hitting a 20 inch steel plate.

riflecompletelarge.jpg

scopelarge.jpg


check out this link for some sick shooting.

http://www.northfloridashooting.com/Misc/2MilePrarieDogs/2MilePrarieDogShooters.htm
 
If you use too much slope in your mount, you might overpower your scope's "down" adjustment range, and not be able to zero in at 100....

The thing to do is to find out how much adjustment range your scope has (some scopes have surprisingly little, e.g. the Nightforce BR scope). Then get a base with no more than half that amount of down-slope.

Another option is to use a two-piece base, or a one-piece base with no slope, but to use Burris rings with changeable plastic inserts - you choose insert sizes to give you however much down-slope you need.

Will you be shooting factory ammo or handloads? 2850fps is very easily achievable with a 30" barrel. 2900-2950 is typically what most full-power ammo will give, and some shooters go to 3000-3050fps. And I think factory Lapua ammo will also easily get 2850fps; so 2850fps is a pretty conservative figure to use.

Run the numbers through JBM Ballisitics and do a little playing around. Choose the "(Litz)" data for your bullet if it is available - in the case of the 155 Scenar, it is (the Litz data uses actual measurements, fitted to the G7 drag curve - it is quite an improvement over using the G1 curve for long range calcs. The simple version though is "use Litz if available" ;-)

A Lapua 155 @ 2850fps, using the Litz data, at "sea level standard" atmospheric conditions, will go subsonic at 1070 yards. At that range, the bullet will have dropped 38.6MOA from a 100 yard zero.

So if you have a scope with at least 80 MOA of elevation adjustment (and some of the 30mm target scope do have this much or more), you don't need a sloped base to shoot out to this distance.

If you have my B&L 6-24X scope with 29MOA of elevation adjustment (beautiful optics, shame about such a limited adjustment range), using an ordinary base you'd have less than 15 MOA of "up" adjustment - you'd be able to get on paper at 600 yards, but not at 700 yards. If this was mounted on a 15 MOA sloped base, you could probably get on paper at 900 yards (27.6 MOA up from 100 yards required), but not at 1000 yards.

My Leupold 6.5-20X (40mm objective) has 44 MOA of elevation adjustment. It could definitely be zeroed at 100 yards with a 150 MOA base, and probably could be zeroed with a 20 MOA base (though if the tolerances stack up against you, possibly not). With a 15 MOA base, there would be about 15 + 22 = 37 MOA of "up" adjustment available from 100 yards. This would be enough to get you to 1000 yards, but would likely run out just before 1070 yards.
 
Yes, your bullets will be subsonic, but that does not mean they will be unstable. Yes, at that range you will likely need an additional 20 MOA of adjustment. As Daniel has mentioned, you will have issues at short range with many scopes however.

Why are your bullets so slow? You should be good for 3000 fps with that set-up.
 
With that scope, you will not get to a mile.

When I took my 223 to a mile with an Elite 4200 tactical scope with approx 45mins of up, I had to set my 100yd zero 46" high. (you can read the article on my website in the rifle tech section) My 80gr Amax landed about 1400yds with that zero. I dialed up and used my reticle for the rest of the trip.

If you want to be able to dial from 100 to 1 mile, you are going to need a scope with massive amounts of up.

the best new product to offer enough elevation is the Sightron SIII LR fixed mag scopes for 2010. rated at 150min of up with a picket fence mildot reticle, these will make the trip. You will likely need 100mins to go 100 to 1 mile.

http://www.sightron.com/index.php?action=view_document&did=1201816362&cat_id=6&id=153

This will be what I am going to mount on my 223 for very LR shooting.

There is a very good change that the Lapua will stay stable after going subsonic but there is only one way to find out. If that fails, the 155gr Amax will make the trip.

Enjoy...

Jerry

PS there are also articles on how to tune you handloads so shooting that far is feasible. If using factory ammo, you need to have no more then 1/2 min of vertical dispersion at 300m. 1/4 min is better. No vertical is better still.
 
Most bullets aren't hurt (accuracy wise) by going subsonic.

FWIW, the Lapua 155 is used by some Match Rifle shooters in Bisley, which is fired at 1000, 1100 and 1200 yards. It will be subsonic before it gets to 1200 yards, but it is a competitive bullet.

jimmym40a2, that scope mount was clearly made by a machinist with way too much time on his hands... ;-)
 
Brutus, download ballistic program from Lapua site. It's the best in the world other than PRODAS and perhaps a couple of other $10,000 + programs, as it uses Dopplar Radar data. Far superior to those using 1890 B.C. science or derivations.

PS, your brother hasn't picked up .22 XMas present.

Regards,

Peter
 
Wow, thanks for the wealth of information fellas!
To add, I certainly can handload my ammunition to a higher velocity.
I am using Lapua brass, and Federal 210M primers.

From what I have garnered here, I think I'll keep my distant shooting a tad shorter, for now. I am a green novice at this, that's a sure thing!

PS: And thanks Peter, plus I'll call my brother and see what is up....

Cheers!
 
I would not go with a 12-42 NightForce. I wanted the same scope for the same reason but settled for the 8-32 instead. Its on my Rem 700P with a 20MOA base. Bulletflight says I need 45.9 MOA to get to 1000yards.
With a lower power scope you will get more adjustment out of it. The 8-32 has 65MOA for elevation and 45 for wind compared to 45MOA for elevation and 35MOA for wind. So with the 8-32 you gain 20MOA. If I had to buy a scope again I will go for the 5.5-22 but I am very happy with my scope.
 
NightforceSpecs.jpg


You can see that the NXS has 45 mins of elevation which means that if your closest zero is 100m and you are bottomed out on your elevation you will have 45 minutes of elevation to play with. This is rarely the case with a standard no taper base, so whatever elevation you take out of the scope to zero at 100 leaves you with whatever is left to get you out to your max distance.

ie. If it takes 10 Minutes of Elev. (from the bottom) to get you to your zero, this leaves 30 minutes of elevation in the turret.

My 6BR takes about 29 minutes IIRC to get from my 300m zero out to 900m so you can bet that the .308 would be more.

I am one of the lucky few that can still get down to 100m with my NF 12-42 BR Scope and Farrel 20MOA bases, I know a few others that cannot and one that cannot zero even at 300yds from his 300m zero. Not that I have a need to shoot at 100m but it's nice to know I can if I want. :D
 
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