What follows is an exchange of questions and answers about extreme long-distance shooting, between myself and Carmen, a member of the Fifty Caliber Shooter's Association. I think you'll find it interesting, which is why it is being posted here. Condor
Condor: Since you're in the FCSA, what's the magnification of choice for the 1000-yard "plus" boys? Is any particular scope used more than others? Are mil-dots popular with the crowd, and why or why not?
Carmen: There was a study of equipment used by the FCSA 1000 yard benchrest shooters published in "Very High Power". The data is from match entrance form questions. From 93 guns sampled in 1997 these were the responses:
|Leupold MK4 (10 or 16x)||22|
|Leupold MK4 (20x-36x)||17 (Premier Reticle modification)|
|Leupold other than MK4||11|
|Mil-Dot||11 (may include some duplex)|
|Other||4 (NightForce scopes)|
The top (smallest aggregate) FCSA heavy gun shooter uses a MK4 Leupold modified by Premier to 24x with a dot reticle.
Why? The Leupold Mk4 is rugged, has good eye relief, has an amazing 140 moa of vertical adjustment and is readily available. The dot reticle allows quick and easy centering on a bullseye target. All of the scopes on the list work. Some of the rifles are tactical designs which are being shot in competition. Other requirements may dictate a larger field of view (lower magnification) or a rangefinding reticle (Mil-Dot or NP-1). When shooting at fixed range targets as in the FCSA matches rangefinding reticles have no added value and actually the wide range of vertical adjustment isn't needed either. It's needed if one is shooting at various ranges to 2000 yards.
Condor: For 1500 yards, would you recommend 20-power, or stay with the 16- Power. This is all in reference to my .338/378 Weatherby Magnum, which I intend to use out to 1500 yards.
Carmen: This starts to get into the area of personal preference and has a lot to do with the quality of your eyesight. Yours is also a "tactical" rifle, not primarily a competition benchrest rifle.
Some tradeoffs are:
My advice is to get the 16X with the 3/4 dot or plex reticle. The 10x has less vertical adjustment (90 MOA) but it's good too. Don't spend the money on the Mil-Dot. At over 1000 yards I don't believe the Mil-Dot will be accurate enough. Mil-Dot accuracy is a fixed percentage of distance and is rarely better than 5%. At 1000 yards that's 50 yards which isn't good enough to not degrade your rifle's performance. At 1500 yards the error would be 75 yards and the bullet is dropping at an even steeper rate.
Condor: If the Mil-Dot rangefinder isn't good for long ranges, what is?
Carmen: At least two companies are selling laser rangefinders in the U.S. which are useful to 1500 yards. They are: NAIT (916-630-8993) and Laser Technology (1-800-280-6113). They are under $2000 and $1500 respectively. They will both range over 2000 yards under optimum conditions (large reflective surfaces). For ranges to 800 yards the Mil-Dot systems works well but you'd probably be better off shooting a .308, not your .338-378. The Bushnell and Tasco rangefinders don't work very well over 500 yards. Even the Geovid is only practical to about 700 yards. None of these help at all over 1000 yards.
If the terrain has sufficient features one can read 7.5' USGS maps to an accuracy of about ten yards which may be a very practical choice. A precision Mylar overlay makes measuring from a map reasonably easy. Some $4000 Russian artillery laser units exist if you can find one that's working. They have a range of over 10 km, but they're not very portable. Even the NAIT and Laser Technology units need a tripod to achieve maximum range. They integrate many pulses over a brief time period.
There are other rangefinding techniques which may be practical for some applications, such as knowing the spacing of section line fences around fields, or knowing the length of city block in urban environments. One may be able to obtain aerial photographs and scale them. They are much better for showing terrain features than maps. There are coincidence rangefinders which used to be used by artillery units. They give decent accuracy in the 1000 to 2000 yard range. They work by measuring the angle between the light paths between what is effectively two telescopes. Surplus ones from Barr & Stroud or Zeiss can sometimes found for under $2000. They are more bulky than the laser rangefinders. There are light weight commercial units but they are useless at 1000 yards and don't outperform the Mil-Dot method at any range. There are long baseline surveying techniques using a theodolite, but while this may be less expensive and more accurate than most other methods, it is difficult to set up. "Estimating" the range simply doesn't work for precision shooting beyond 1000 yards.