so a few months ago I decided, after having my carbine all squared away, that i should totally try out variable scopes and swap out the aimpoint, and picked up one of the new SWFA 1-4s that came out around black friday.
i mounted it and took it to the range and made sure i was around 2 inches low at 25 yards at my indoor, but havent had a chance to properly zero it at range. still, i’m digging it. An unexpected plus, since i focus the diopter to my right eye, its helped tons with my natural cross dominance, and i’ve startled my dog dozens of times running around the house dry firing with it.
i’ve noticed a couple things though. First, and it’s probably my error in mounting the scope, but when i zoom up to 4x, i have to place my face closer to the eyepeice. i figure it’s not a big deal as if i’m at 4x i’m probably proned out anyway and my face will naturally be a little closer anyway. last night, while dry firing in the house (that poor thermostat and fridge magnet have so many imaginary rounds through them…) i noticed that when i zoomed in to 4x, the crosshairs would get blurry on what i thought was the correct diopter focus. After playing around with it a good bit i may have found a better spot, but it feels a little strange on 1x now. More fiddling, target blurry at 4x but all good at 1x.
Now, the target was just a magnet on my fridge, no more than 15 yards away…is this to be expected? Will it be all clear at 100 yards?
It makes me question if i mounted it/focused it right from the beginning. Do you let your eyes focus on the crosshairs, or hard focus on the target like a red dot? The instructions i was given for setting the diopter was to look at a while wall, bring up the rifle, and adjust until the crosshairs appear crisp naturally, which is what i did the first time.
Any pointers/thoughts/concerns/you dude you’re totally stupid you’re supposed to do it this way comments?
Another tip is to look away from the task. Go look at a book. Go look at a bird out the window. Whatever. Just get that scope out of your face. Then whip the thing up. Instantly, or nearly, the reticle and target should both be crisp. IF not, you have adjustment to do.
Why?
Because the eye (assuming you are under 45-50 in most people) will “accommodate” it will flex the lens to focus, effectively “correcting” diopter. Of course this is not optimal. You want to get the diopter adj. out of your gear…not your eye. So don’t sit there dicking with diopter on the optic for very long at a time at all ( a few seconds ), or your eye will start “turning the diopter” itself, and you will be “chasing a moving zero”.
The higher the magnification the less forgiving your eye relief is and the harder it is to focus on a target that is significantly closer than the optic’s collimation distance.
Some scopes don’t change eye relief much due to magnification but many do. Get in the habit of setting your eye relief at high magnification. Then when you turn the magnification down you won’t notice a problem. What was said earlier about the diopter being for focusing the reticle is absolutely right. Point the scope at a white background that’s so close you can’t focus on it. Set your diopter like this and your image can’t mess you up. Your scope is probably collimated for 100 yards so check it at that distance and see if the problem still exists. I would not expect you to be able to get a target in focus at 4x at distances inside your house. That’s what 1x is for. Anything closer than 30 yards is going to form an image so far from your reticle that you won’t get it and the reticle in focus at the same time.
I will add that every variable scope has some diopter shift from low to high but it’s not usually enough to cause the problem you’re seeing unless you’re 50+ years old and your eye can no longer accommodate for much diopter shift. Hope that helps.
With some scopes, the eye-relief will change depending on the magnification—typically getting shorter at higher magnifications. So that’s normal for your SWFA. You’d want to mount the scope for the eye-relief and magnification you will be shooting at the majority of the time. In my case, I shoot at 6x 99.99% of the time. So I mounted the scope for that magnification and eye relief.
As for diopter settings, you adjust it properly by aiming scope/rifle up to the sky where you can see some clouds (or at least something in the far far distance at infinity). Lower the rifle and look at the sky. Raise the rifle and look through the scope quickly. Adjust diopter so clouds are in focus. Repeat a few times until your crosshair and clouds are both in focus @ infinity. You do this because your scope has a preset, non-adjustable parallax setting. Which is calibrated so that reticle and target focus are both sharp and parallax-free at a certain distance (typically 100 yards). So if you set the diopter to be in focus at X distance, but then you look at something closer—like something 15 feet away on your fridge—it will be out of focus. When you hit the range and shoot at a longer distance, it shouldn’t be an issue.
I personally like to adjust variable power optics, at highest power, because that’s when the eye box most unforgiving, and you’re more likely to see vignetting. Try to center yourself on that vignetting, as if you’re attempting to co-witness it, to do so you’ll have to see if you need to adjust your length of pull, rail position of the optic, and comb height all awhile trying to maintain a proper check weld where you’re not muscling anything in place. I close my eyes, act as if I’m about to fall asleep, then open my eyes, and check if I’m centered and try to reduce the vignetting as much as possible. I adjust and repeat this process as necessary, before I even touch my ocular focus. You may also need to check this in various positions, not just in prone. I reiterate through the process through a kneeling, and standing position, as well as off a Manfrotto tripod. I find for my ergonomics, if I’m shooting on a barricade or tripod, I have to collapse the stock slightly to maintain the ideal eye relief.
Once I’m ready, I adjust my ocular focus on a bright wall, before heading out to BZO. I look out of the scope and back in and evaluate if the reticle immediately appears or not. I go counter or clock-wise on the adjustment till it’s crystal clear. Then I touch the parallax adjustment.
Don’t trust the parallax adjustment that if it’s marked on the knob. If I have time before sending rounds down range, I try to calibrate my parallax knob, scoping targets at known distances at 100 yds increments, or if I don’t have immediate access to a KD range, use my LRF and do the same anywhere outdoors. Simply adjust counter or clockwise on the knob till the target is clear at that particular known distance, and mark via sharpie that distance on your knob. This way, in competition or otherwise, I’m not fiddling around and can go straight to the proper adjustment.