Rifle Scopes If matches are mostly shot using 15x or so why have a 27x scope?

[LAW-DOG]

Magnification is different for everyone, people with worse vision might prefer more than people with 20/20 vision. The differences between powers aren’t big as it sounds. Take the target distance divided by the magnification will give you its value. 15x @ 1000 yards= 66 yards, 20x = 50yards, 25x = 40 yards, 35x = 28.5 yards, 50x = 20yards. 50x is when you start to see a big difference in magnification as it is twice as powerful as a 25x scope

 

[pewpewfever]

As others have stated, most scopes lose clarity as you approach maximum magnification, so you want some headroom unless you’ve invested in a really pricey scope. Another factor, I’m told, is that the higher magnification is useful for reticle ranging, and then you back off to a more useful magnification after determining range. Not usually a factor at matches though.

 

[LAW-DOG]

As others have stated, most scopes lose clarity as you approach maximum magnification, so you want some headroom unless you’ve invested in a really pricey scope. Another factor, I’m told, is that the higher magnification is useful for reticle ranging, and then you back off to a more useful magnification after determining range. Not usually a factor at matches though.

Mirage & fov is anther big factor, at high mag it’s hard to spot misses. My uncle uses high mag scopes for 22-250 to help see close to mid range paper target shooting

 

[Greg Langelius *]

One other critical factor to consider is the elevation/windage adjustment range.

When one adjustment is brought to near its limit, there will be a corresponding limitation on the other adjustment. It feels like the other one is binding.

If that other adjustment is already near its limit, you may actually have more adjustment range left on the one you're adjusting, but it just may not be available since the other one is already creating a binding effect.

For example, when the elevation is near its top limit, windage adjustment may become severely limited; precisely were, out there, it's most needed. There is no substitute for adjustment range when you need it.

The solution does not involve fiddling with the knobs. It requires modification to the mounting base, done well before the scope is committed to competition.

Start by zeroing at the near distance (I use 100yd), then adjusting the scope by the calculated amount of MOA/Mil needed to be on target at the median range where the targets will be situated. Ideally, this will be located at the median range of adjustment available.

If it is, you're set. If not, mods need to be made so the binding limitations never get reached. Depending on the scope's range of elevation adjustment, the necessity of these mods will range from small to great.

Bases come flat, 20MOA, and other values. Compute how many MOA you need in order to augment the amount available so that the median shooting distance falls at about the median adjustment range.

That necessary augmentation value may not be one of the ones that are readily available.

Fret not, there is another way. An available base with a lesser MOA value can be shimmed to adjust the MOA value, then bedded to allow it to be custom fitted to the receiver. Shim the rear end of the base, then sight the scope so that at the 100yd(?) zero, there is still at least 5MOA of down adjustment remaining. At the near distance, some windage adjustment limitation can be acceptable, since less is usually required up close.

I use strips from aluminum beverage cans for the temporary shims. How much shim value is needed depends on the distance between the scope rings and the length of the base, but very few shims are needed.

I do this by setting the elevation at 5-10MOA from the bottom, then adjusting the shims until that crosshair position (without touching the elevation knob) delivers very close to the proper height on the 100yd target.

This is a tedious process that often requires multiple passes at disassembly and reassembly of the mounts and rings. This is why we do it well in advance, at a moment when time is more available. But the value is that when you get it right, the median elevation adjustment range (at your likeliest working distance) will allow the greatest amount of windage adjustment. That's something that needs to have little of no limitation.

If the needed windage correction falls outside the scope adjustment range at this point, the screw holes in the receiver are likely out of alignment with the bore axis. This is a serious problem that is outside the box where this process is concerned. It needs to be corrected by a competent gunsmith.

Once the shim value is determined, degrease everything, prep the receiver with release agent, Petroleum Jelly to the mounting screws, and apply bedding resin to the bottom of the base. Tighten the base onto the shims and receiver, and snug the screws down gently. Quickly wipe away any excess. Once cured, pop it loose, clean away the release agent, excess resin, and Petroleum Jelly; and reassemble the mount.

You could forego this step, and still get away with things. But doing it right has value, and having a custom tuned mount can provide the most versatility when one must obtain a sighting solution.

My LR precision rifle's base is custom tuned to about 33MOA, and zeros at 100yd at about 5MOA from the lowest elevation adjustment. At my current altitude, the rifle has a supersonic arrival range of around 1400-1500yd. The mount accommodates this easily.

Greg