Mounting a scope can be tricky, if not treacherous

COMMON SCOPE MOUNTS, from top down, are Weaver Style, Leupold Dual Dovetail, Leupold/Redfield/Burris windage adjustable and Tactical/Weaver/Picatinny.

 Mounting a scope on a firearm can be one of the easiest or most difficult tasks that I take on.

If all of the manufacturers involved get everything right, the holes will be top dead center on the firearm, the mount bases will have their holes right where they are supposed to be and the screws will be just the right lengths, the rings will have the two halves of each ring totally concentric and the scope will not have any issues, with plenty of adjustability to zero the rifle.

Surprisingly, this is usually the case.

When things go wrong there are a few remedies that experience has taught me but other times you need a lot of tools, equipment and time. It’s amazing that the manufacturers of firearms cannot get their mount holes in the same place every time. I am sure they use a jig to drill and tap these mount holes so I don’t see how it gets screwed up (pun intended).

Whatever the cause, they do get drilled off-center and something has to be done about it. The easiest fix is to use a mount such as the popular windage-adjustable Leupold/Redfield/Burris system, in which the front ring goes into a dovetail at the front of the base and then turns 90 degrees to lock into place. The rear ring is held flat on the base but has two opposing large-headed screws that allow the whole assembled scope and rings to move laterally across the top of the rifle.

This can make up for quite a bit of mount misalignment but is not the strongest setup out there. It is plenty strong, however, and has been used for decades. I even had this system on my 458 Win. Mag. for a couple of years with no ill result. This system is also available for many different firearms, but not all of them.

The Weaver system is by far the most universal and used for attaching all kinds of things to firearms, not just optics. Everyone who uses firearms has encountered the Weaver system on a rifle to mount a scope, a handgun accessory rail to mount a light or laser under the barrel, or in the military’s version called a Picatinny rail at the forend of an M-16/M-4 or AR-15.

These bases are made for almost every sporting rifle ever made and many military rifles as well. In fact, if you want to spend the time trying different bases you can probably mount a Weaver base on virtually every long gun that ever existed.

The bases themselves are cheap, light, strong and simple. It’s a 7/8-inch dovetail with a cross slot. The ring has a corresponding cross bolt that acts as a recoil lug and locks into the base slot to keep the scope from walking off of the front of the bases. There is a big claw on both sides and a large nut to lock it all together.

It has been derided as weak because of the aluminum parts involved but in 30-plus years I’ve never experienced a problem with them.

The standard Weaver rings are kind of homely but they are strong, because of the way they hook on one side and strap over the top of the scope, then are secured with two screws on the same side.

It is possible to dent the scope’s tube if the rings are tightened aggressively. This is easy to do as well, because as you tighten one screw and then the other it’s easy to get carried away.

However, because of the universal nature of this system there are about a billion different manufacturers of rings to choose from. One of the most useful ones is the Millett windage adjustable rings.

Both of these rings are adjustable, so quite a bit of misalignment can be compensated for with them. I keep them around all of the time to correct problems caused by home “gunsmiths” who have drilled and tapped their own rifles for mounts. Sometimes the only cure is a welder, grinder, file and re-drilling to fix these abominations.

One was so bad that I actually had to weld the base to the rifle to save it; the top looked like Swiss cheese.

Many times rifles need elevation correction; this is much easier. Several manufacturers make shims of varying thicknesses just for the purpose of adjusting the elevation of the scope base(s).

For some reason Weatherby Mark V rifles tend to need more adjustment for windage and elevation, especially the older Japanese manufactured ones. They are not all this way but much more commonly than other rifles.

Just two days ago, however, I had to re-drill a current Winchester Model 70. These tend to be some of the truest, best-made rifles available but this one definitely wasn’t correct. I had to oversize the holes from 6-48 to 8-40 and offset the rear to the left and the front to the right, then it was dead on.

I’ve also seen quite a few bases come with screws that were either too long or too short. A few years ago Leupold was sending out their Ruger 10/22 bases with Torx screws that were just long enough to get a bite in to these rifle’s aluminum receivers, then the installer would give them a good turn to seat them in and rip the threads right out of the top of the rifle. They also were sending screws for the Winchester Model 70 that were too short; however, since the receiver was steel, it ripped the threads off of the screw, which is a lot easier to make right.

Long screws end up not letting the base get secured down to the top of the firearm. Obviously, this creates a wobble but part of the problem is also that the friction between the base and firearm is also part of the equation that hold everything together.

Long screws also end up going through the receiver and into the action, which interferes with operations. Lever, pump and bolt actions will end up with their bolts locked up hopelessly into the action. Bolt actions will end up with turn-bolts that won’t turn or ones that can’t lock up.

One of my worst nightmares is the rare occasion when a Ruger shows up with a mount alignment problem. The base is a machined part of the receiver in most cases and the rings are proprietary. There is absolutely no way to adjust for windage or elevation.

Millet makes a ring that allows for a little bit of windage adjustment but elevation is still a problem. No, you cannot shim the inside of the ring – only the base. The rings are cylindrically cut to take a 1-inch, 30mm, etc. scope tube. Any shim you put in there reduces that diameter and risks damaging the scope’s tube.

Burris had the ultimate solution for this problem with their
Posi-Lign and, later, Signature rings; but, sadly, they are no longer made for Ruger’s creations.

These rings had polymer inserts that were self-aligning and available with eccentric inserts that allowed corrections in 5, 10 and 20 thousandths of an inch. The polymer construction of the inserts also made it almost impossible to scratch your scope with the scope rings and they compressed enough to really get a hold on the scope tube.

These inserts could be used on either or both ends of the scope and could be installed at any index around the ring. Up to .040 of an inch of adjustment could be made at any angle. I mourn their extinction.

Care should also be taken to keep the ring halves oriented with each other as they were manufactured. Most steel rings, especially those on  older Rugers, are reamed just like a connecting rod in an engine and swapping the caps around is not a good idea. Making an orienting mark with a pencil is a good idea. If I know they are currently correct, I will even stamp an indexing mark into them.

Many styles of Quick Detachable mounts are available and the Weaver rings are usually very repeatable on and off of the rifle, even though they are not really intended for this use. The Leupold QD system is the cream of the crop, as far as I’m concerned. See-through mounts stink; they eliminate any possibility of a solid cheek weld on the stock and the scope usually ends up getting used as a carry handle since it’s sticking up in the air so high.

I used to frequently run across shooters who preferred the one-piece Redfield/Leupold/Burris bases over the two-piece version, as they believed they were stronger.

They would probably be right except that the one-piece bases almost always only use three screws to attach the base to the rifle; the two-piece version uses four.

Because of the screw hole misalignment I’ve already mentioned, sometimes that single rear-mount hole is not on the same plane as the front two. The installer starts all three screws and then torques them down; this puts everything in a bind and occasionally the single rear screw shears off. Now the back of the scope base is just floating in mid air, not attached to the receiver at all.

My favorite mount for sporting rifles is the Leupold Dual Dovetail and Burris Double Dovetail, two names for the same system. This system makes use of the very strong front dovetail of the previous system but also incorporates that 90-degree dovetail in the rear as well; it doesn’t get any simpler than that.

Of course, this does away with the windage adjustability and sacrifices it for strength so the mount holes on the rifle had better be right and/or the scope needs a lot of internal adjustment.

Speaking of, the early Leupold scopes had very little, which almost necessitated the use of their popular windage adjustable mount in order to get sighted in.

I would be remiss if I didn’t mention the tactical mounts so in vogue now. These systems are very strong but can also be very expensive.

My pick of these is the Farrell G-Force available with 20 MOA tilt. This tilt is there for shooting extreme ranges, where the bullet drop is so much that the internal adjustments of the scope cannot handle the amount of drop involved. You can also accomplish this with the Burris Signature rings by using the eccentric inserts in the rings to tilt the back of the scope up.

I only have one rifle with these mounts on it as they are totally unnecessary most of the time. The single-plane, rigid mounting these Tactical bases offer pretty much eliminates any need for lapping rings.

On that subject lapping rings is never a bad idea but it does dedicate that set of rings for that particualar rifle in the orientation they were lapped in. This lapping process is accomplished by using a lapping compound on a rod of the appropriate diameter to remove small amounts of material at the high spots of the rings to make eveything line up correctly so nothing is bound up when the scope is mounted.

My final point is on bore sighting.

Technically, it’s collimating. Bore sighting works wonderfully well. You remove the bolt from your rifle and actually look down the bore, perfectly straight, and visually center the aiming point into the bore. Then adjust the scope’s reticle to the same point.

Collimating is what we do in the shop with a tool. This is not nearly as fool proof and just aligns the muzzle to the scope’s reticle; the bullet might not actually go there. I’ve seen box store employees take the credit if their “bore sighting” was dead on but it’s just luck.