How to Mount a Scope

rifle-scopeHow to mount a scope and sight in your rifle.

Mounting a scope and sighting in a rifle — it may sound like a simple process and it can be, if done correctly, but it can also be the prelude to an array of problems. The worst of such problems could be a missed shot at a buck of a lifetime. It seems that on nearly every trip I make to the range these days I end up helping someone having a problem with a poorly mounted scope or with sighting in a rifle.

Long ago I lost count of how many scopes I have mounted or how many rifles I have sighted in, but it is considerable. During these many sessions not all has gone smoothly by any stretch. I have encountered about every problem one could imagine from scopes that did not have sufficient internal adjustment, rings that were too low or high for the scope, rings that would not allow for sufficient eye relief, stripped screws, screws that were too short or long, and the list marches on. What I will attempt to do here is to provide a simple guide to mounting a scope and sighting in a rifle that should not only put you on target but keep you there.

Mounting a Scope

Prior to getting down to the basic procedure for mounting a scope, I believe it is important to clarify the need for top quality rings and bases. While they may cost a bit more, if they are mounted correctly, they will last a lifetime and never fail under the harshest conditions. So don’t shortchange yourself, purchase quality rings and bases.

The first step in properly mounting a scope is to acquire the correct rings for both the size of your scope and for the rifle you intend to mount it on. For example, if you were to purchase a Leupold VX-III 2.5-8×36 for a Browning A Bolt long action rifle such as a .270 Winchester, you would refer to Leopold’s base fit and ring height information guide. The guide will provide the correct height for the rings and the correct part number of the bases for that rifle, depending of course on the style and finish that you are seeking. In this case the guide tells me that I can use low rings and for a standard two-piece base in a matte finish the part number is 50030. Once you have acquired the correct rings and bases for mounting the scope, not much else is needed except a gun vise and some Loctite threadlocker 242. Now the last two products are, of course, optional but recommended with the following procedure:

  • Clean all the rings and bases of any excess storage oil or grease.
  • Place your rifle in the vise and secure.
  • Remove screws from tapped base screw holes on the rifle receiver. These are very tiny slotted screws so you will need a jeweler’s screwdriver to remove them. The use of an oversized screwdriver can easily mar the metal around the screw hole on the receiver.
  • Correctly position the rear base and after placing a small amount of Loctite 242 on both screws, tighten the rear base solidly to the receiver with the proper Allen or Torx tool provided with the rings/bases, or even better use a Torx driver.
  • Repeat this same procedure for the front base.
  • Then take the front ring and with a wooden dowel that is only slightly smaller than the ring diametre, turn the front ring into the base until it lines up correctly.
  • Next, partially remove both windage adjustment screws on the rear base. Then place the rear ring in position and slowly but equally turn in the two rear windage adjustment screws until they are partially tight.
  • Take off the top half of each ring and place the scope into position. Make sure it lies flat in the rings and that it is not off centre.
  • Now you can replace the top half of the rings and after placing a small amount of Loctite 242 on each screw, tighten them only to the point where you can still move the scope back and forth with just a slight amount of friction.

Remove the rifle and scope from the vise and mount it to your shoulder. When in place, slowly move the scope back and forth until you have attained the best sight picture possible. You may even want to try it while wearing your everyday hunting jacket as this setting can change depending on what you are wearing. At this point you also need to rotate the scope in the rings in order to level the reticle. The elevation reticle should be absolutely horizontal when the rifle is mounted to your shoulder. I always check it against a known horizontal line such as the top of a wall or a power line. When both of these adjustments appear to be correct, tighten one ring screw on both the front and back ring just sufficiently to hold the scope in place. Now mount the rifle a number of times to make sure it is still where you want it. The correct eye relief here is important, so don’t move on from this step until it is exactly right. In fact, I always put the rifle down for a bit and then come back a number of times to ensure that I’m still happy with the positioning of the scope. Once you are satisfied, securely tighten all the ring screws with small but equal increments, alternating from side to side and front to back.

The last step is to secure the windage screws in the base. There are potentially three methods of setting the windage screws and I will describe each. The first is simply that once you have made whatever windage adjustments are necessary on the range and have tightened them in place, leave the screws as they are. I, however, prefer one of the next two methods. On the range, when I’m satisfied that my sight settings require no further windage adjustment, I first remove the left windage screw and place some Loctite 242 on it, I then return it and tighten it. I then repeat the exact same process with the right screw. The final method was recommended to me by a top-notch gunsmith and employs the same process but prior to replacing the left screw apply Loctite 271, which will secure the left screw indefinably. But only apply Loctite 242 to the right screw, which will then allow you to remove the scope from its bases by removing only the right screw. The scope can then be returned to its bases with virtually no readjustment in windage being necessary once the right screw is again tightened back in place.

Loctite 242 will aid in setting screws but allows the screw to be removed and is blue in colour. Whereas 271, which is red in colour, will permanently set screws that can then only be removed with intense heat. Great care should be taken to use 271 only where a permanent solution is sought such as on a left-hand windage screw.

Sighting In

The first step in sighting in any rifle is to get range ready. I have a range box with all the necessary equipment that I will need for the range and it includes:

  • Front shooting rest support and rear bag support
  • Spotting Scope
  • Boresighter
  • Various tools and screwdrivers for adjustments to rifle, scope, rings and bases
  • Ammunition for the rifle or rifles I’m shooting that day
  • Notebook and pencil
  • Targets
  • Stapler
  • Hearing protection muffs

Once at the range and every thing is in place, I set my first target up at 25 yards and proceed to bore sight the rifle. This can be done quickly using a boresighter or you can remove the bolt from your rifle.With your rifle securely seated on the front and rear rest, look down the barrel and centre the bore on the bull of your target. Then, without moving the rifle, adjust the scope to bring the crosshair onto the centre of the bull. If you don’t have a bolt-action rifle, I would highly recommend the use of a boresighter as it can save you ammunition, time and a lot of aggravation getting your first shot on paper. Once you are satisfied that you have the rifle properly bore sighted, fire your first shot at the 25-yard target. Adjust both the windage and elevation to centre on the bull and fire another shot to confirm your settings. Then, and only then, move out to 100 yards and fire a couple of shots to confirm where your settings are at. Last, you can now make the final windage and elevation adjustments necessary to finalize where your point of impact should be. I prefer to have most of my rifles shoot dead centre for windage but about 1½ inches high, which will zero most rifles at 200 yards.

I would then fire a number of three shot groups to ensure that the rifle and scope are maintaining your settings and, if they are, you are now ready for any hunt that you may have in mind.

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