This article gathers together observations from three trips to the unknown-distance (UKD) range at AIMA in South Georgia. The range is constructed on mown, coarse grass and features large 20”x40” steel silhouettes out past 1,700 yards to which we added small 12”x24” ones. I shot with an AI AW in .308 topped with an SWFA 5–20x50 scope mounted on an 18 MOA rail all three times. My SAS Ti Arbiter suppressor came along on the third trip.
Hitting at 600+ yards depends almost entirely on atmospheric conditions, particularly wind and mirage, assuming that you have your fundamentals squared away and are shooting a decent system. Wind blows the bullet off course while mirage limits visibility. Visibility is critical not only for lining up on the target but also for observing the bullet trace and impact. Heavy mirage causes the target to shimmer and hides the trace and impact. Steady winds aren’t that tricky, but rapidly changing ones, particularly if the area lacks reliable wind cues, can prove quite vexing. Wind and mirage tend to be strongest in the middle of the day and weakest around dawn and dusk. In ideal conditions, hitting the small steel targets at 1,000 yards isn’t particularly difficult, but in tricky conditions, even 600 yards proves challenging. It’s easiest to make long shots around dawn and dusk. During the day, the sun heats the ground to cause mirage and the wind picks up. And when the sun is out, a hat doesn’t work particularly well for keeping glare out of your eyes. The problem is that the scope bumps the brim of the hat during recoil, shoving your head of the way and making it difficult to observe the bullet’s impact. A sniper veil works much better.
One trip featured challenging winds where the windage hold for the 600-yard target would rapidly vary ~2 mils, twice the width of the target. The only wind cues were the treetops and mirage, which was generally running horizontally. I had serious trouble connecting at 600 yards under these conditions and was shooting with two other guys: one who also had a .308 and another who had a .260. The other 308 shooter had the same trouble as me, while the .260 shooter had little trouble hitting that target. He had assembled some very precise ammunition, but some of the credit goes to the more efficient 6.5 mm bullet—his wind holds were just over half mine. So a wind change that would throw my bullet off target might only push his to edge of the steel. I suspect that a good shooter with a .260 could beat a great shooter with a .308 in long-range practical shooting. I was admittedly at a disadvantage shooting 175 SMKs from a 20” barrel. The added muzzle velocity from a 26” barrel and Lapua 155 Scenar bullets would give the .308 a fighting chance.
In retrospect, my big mistake was chasing the wind instead of waiting for it to return to a known state. I’d observe my miss, adjust my hold, and fire a follow-up shot. But the wind would already have changed and my follow-up shot would miss as well. The right thing to do in those circumstances would be to adjust my hold but wait until the mirage looked the same before sending the follow-up shot. Wind doesn’t blow at a constant speed, but it does tend to have a regular speed interrupted by gusts and lulls with these states repeating in an observable pattern. Waiting for the wind and not rushing the shot is one of the hardest parts of long range shooting to learn. If you try to force your shots you will miss.
This is where having a good spotter comes in. The military learned long ago that the shooter, affectionately known as the trigger monkey, has enough to do just keeping the crosshairs lined up and staying ready to send the shot at a moment’s notice. This is why sniper teams consist of both a spotter and a trigger monkey. The spotter’s job is to get the team in the area of operation (AO), read the winds and ranges, and assist the trigger monkey. The trigger monkey's job is to follow the spotter to the AO then pick the shooting position, direct setting up of a hide, and run the weapon. Once in position, the spotter will call out the elevation and windage adjustments while the shooter simply follows directions.
Direction from the good spotter will sound like:
"Hold left 1.5 mils."
"Okay, send it."
And if you didn't break the shot quickly:
Because he saw that the wind had changed.
It’s hard to both call wind and fire the shot. Just running the weapon and waiting to hear “send it” takes a lot out of you. The spotter will also use a scope that offers a wider field of view than a riflescope, which eases observing the wind. It’s possible to keep both eyes open and use a spotting scope at the shooting position, but this gets quite fatiguing and makes it difficult to keep the rifle ready to fire.
A critical skill for solo shooting is the ability to both call your shot and spot the impact. Calling the shot refers to seeing the crosshairs at the instant the shot exits the barrel. This requires not blinking and keeping the crosshairs on target when the rifle fires. A good way to tell is that if you can see the muzzle blast then you’re not blinking.
I always hold for wind instead of dialing, as I find that this keeps me more in touch with it. I tried dialing in the past, but it tends to put the wind out of my mind. It’s almost like you’ve dealt with the wind by dialing and forget about it. But the wind is constantly changing. Combining dialing and holding seems like asking for trouble.
The equally spaced steel provided a great opportunity to confirm elevation needed for each distance. After that, it’s good fun to range UKD targets with the mil reticle, dial for elevation, hold for wind, and whack them with a round. Doing this with a second-focal-plane scope must be a pain, as you'd need to do another step of calculations to adjust for the magnification setting on the scope. The Horus reticle makes a lot of sense for UKD shooting despite its busy appearance, but I’m just fine dialing elevation for range and holding for wind with my mil reticle.
I was surprised that I’ve never felt the need to go above 12–15x on my scope when shooting long range, even when tagging the 1,500-yard steel. Acquiring targets at higher magnifications becomes difficult due to the narrow field of view. But the main problem with higher magnifications comes from atmospheric effects: the scope is mostly just magnifying mirage without adding additional detail. I think that magnifications above 20x are mostly useful inside of 100 yards or in exceptionally clean air.
The AIMA UKD range has a number of berms, and it was fun to realize that bullets don't travel in straight lines. A couple times, I could only see the head of a target behind a berm. But I'd put the crosshairs in the dirt where the chest would be and lob a round over the berm to get a center hit. This same arcing trajectory also complicates identifying the corrections needed for misses. A puff of dirt kicked up behind a target could mean that the shot went high with good windage. But it could also mean that the shot was good for elevation, just missed to the side, and the wind acting on the bullet blew it more in line with the target. In these cases, it’s critical to catch a bullet trace to see what’s happening downrange. Seeing how far a bullet hooks off course before getting blown back on target can be quite an eye opener. Catching a glimpse of the trace and seeing the impact requires building a solid shooting position and coming straight back on the trigger without jerking. The details of executing that are beyond the scope of this article but presented crisply in Rifles Only: Precision Rifle Volume 1.
One of the big surprises has been the performance of cheap Prvi Partizan 147 gr. 7.62x51 ammo, which is good for ~2” groups at 100 yards. On one trip, we had the large steel targets set every 100 yards out to 1,000. In still air, that ammunition hit consistently out to 800 yards, although it required a surprising elevation increase to get from 700 to 800. Most likely, the bullets slowed to transonic speeds shortly before 800 yards, lost stability, and started to tumble, rendering them useless past 800 yards. This is a known problem for 168 SMKs as well.
Southwest Ammunition’s 175 Sierra Match King (SMK) match loads work quite a bit better, which isn’t surprising since they’ve printed sub-1.5” groups at 300 yards and the 175 SMK is known for transonic stability. In still air, they scored 7 for 10 on one of the small steel targets at 1000 yards and 2 for 5 on a large one at 1,500. The latter required 22.5 mils of elevation, which exceeded my scope’s adjustment range, so I dialed in 15 and held over another 7.5.
My Orion Apex 102mm continues to work very well as a spotting scope. I’ve had to chance to use a range of scopes including budget models by Konus, mid-range ones by Nikon and Leuopld, and high-end ones by Kowa. The Konus models don’t work so well, offering poor resolution and contrast, particularly off center. The Nikon and Leupold models give similar resolution to my Orion but slightly better contrast and a more compact package. The better contrast makes it easier makes it easier to spot bullet traces. The Kowa scopes deliver by far the best image of the scopes I’ve examined. But when I upgrade my Orion, I’ll look for a scope with a mil reticle for giving precise adjustments, even if it means sacrificing some optical performance.
Shooting next to someone with a muzzle brake isn’t much fun thanks to the added blast. You definitely want plugs and muffs in such a situation. A better scenario is shooting with a suppressor and finding that the folks on both sides of you are running cans as well.
Last edit: 12 December 2012