Light Gunsmithing

Some time ago, this column looked at the screws used to attach scope rings to scope tubes and scope bases to rifle receivers. It was slanted toward sporting rifles since they are the type of most interest to those who do their own gun work. Little was said about fasteners that join scope rings to their bases because all are at least adequate for the job. Once tightened, they stay in place for years with no tendency to break or work loose, as do the smaller screws.

While optical sighting devices and the means used to attach them to rifles were changing when that earlier column was written, both have changed drastically since then. No longer are fixed power scopes with 1-inch diameter tubes mounted as low as possible to allow quick-sighting in the field. Instead, large to downright huge scopes have objective lenses the size of astronomical telescopes and are covered with turrets, dials and adjustable rings. Such scopes have to be mounted so high that a conventional stock comb is useless. A plastic stock with an adjustable/removable plastic comb is often required. Conventional bases and rings can no longer be used to attach such scopes. As a result, many rifles look like they should be displayed on a pegboard at the local farm and garden store rather than at a gun shop.

Then there is the application of today’s optical sights. Red dot sights in their several variations are replacing conventional open iron sights. None attach using standard scope rings and bases, but instead clamp to a section of Picatinny rail screwed to the receiver/barrel. The rail may be as long as the receiver, extend out on the barrel a few inches or even stretch to the muzzle!

With their unlimited eye relief, red dot sights can be attached anywhere on the rail. So can various crude open sights. Of course, standard scopes with proper rings also fit Picatinny rails, as do long eye relief pistol scopes and scout scopes. All this stuff is quickly removable, replaceable and switchable on one rifle or among several. No longer is the optic-to-base attaching screw tightened once and ignored for years. Sights can be changed a couple of times a year or a couple of times a day, depending upon use or hunting conditions. Optic-to-­base attaching screws received considerable wear and abuse from overtightening.

The Picatinny rail is essentially just an elongated Weaver Detachable Top Mount base, but with equally spaced transverse slots instead of just one or two. Since Weaver bases have been available for at least 70 years, there are a lot of Weaver scope rings in circulation. Much switching (accompanied by overtightening) leads to wear or bending of the attaching screw, nut or clamping plate they pass through or thread into. This is totally unnecessary.

If the optic frame or rings connecting it to the Picatinny base are first pushed forward so the attaching screw contacts the transverse base slot, then even if only moderately tightened (20/25 inch-pounds) it is pulled down against the angled surface of the rail. There can be no looseness in the system. It’s impossible. The only fault can be shearing of the 6x48 tpi screws holding the rail to the rifle’s receiver.

Unfortunately, the usual process consists of slapping the optic onto the rail, moving it until the attaching screw falls into a slot, then bearing down on the attaching screw with one of those annoying magnetic tip screwdrivers holding whatever tip was last used. Since these screws have larger diameter heads and wider slots than other gun screws, the result is damaged slots and overtightening. This can be prevented.

The funny looking green things shown in the photos are often called butterfly wrenches for obvious reasons. They aren’t really wrenches, but screwdrivers designed for use where torque is to be limited. Since they are short, slipping out of the screw slot is also prevented. The blued one was once handed out by Weaver. They are quickly made with a hacksaw and file from scrap sheet steel.

Sheet steel is produced in specific thicknesses or gauges. Thickness of 13 gauge is .0897 inch and is perfect for many of the screw slots on all types of optics. Thickness of 12 gauge is .1046 inch, which works for the rest, or a couple of file strokes thins the business end enough to fit.

The wide-nosed butterfly fits old Weaver rings and many other makes. The wrench with the narrower nose fits newer Weaver rings and old side mounts used on countless .22 rimfires. Screw slot damage and overtightening are now prevented because it’s impossible to apply enough force with just the fingers for most folks to damage anything. Make several and scatter them around so one is always handy!

Another photo shows a short, round-bodied screwdriver. The T-handle is made from a 2-inch long, .25-inch diameter roll pin. Its only use is Redfield all-steel scope mounts, once very popular for hard-kicking rifles. The screwdriver end is easily filed on a piece of half-inch round stock. It makes much more torque possible than the butterflies, but it’s necessary for the Redfield attaching screws. Plus, the short length prevents it from slipping out of the slot, which is so common when using a long screwdriver.

Getting back to modern Picatinny rails, it is logical that as rifles look more and more like garden tools, the slotted head screws would give way to hex heads. The one shown in the riser block on an AR receiver is a half-inch (or maybe 13 milli-things, which is the same). First impulse here is to grab a ratchet wrench, but that will twist off the head or damage the locking plate before much resistance is felt. The proper tool is a nut driver. This is a screwdriver shank and handle with a hex socket forged on the end. It can’t slip off the screw head and is vastly superior to a slot head and screwdriver. Nut drivers are used in electrical work and are available wherever tools are sold.

Also seen are attaching screws with Allen heads and Torx heads. The only way to deal with these is by using the proper tool. Now we need not only the three screwdrivers we made earlier, but both normal and metric Allen wrench sets, normal and metric nut drivers and a few Torx drivers. Good heavens! Can this be made more complicated?

Lastly, a situation should be mentioned that doesn’t directly involve the optic/Picatinny attaching screw. This is damage (impact, dents, deep scratches) to long rails in areas the currently mounted optic base doesn’t cover. When that optic is switched to one that fastens to another part of the rail and covers the raised metal around the dent, proper attachment is impossible.

Worst case is the optic base is loose on the rail. The best case is point of impact moves if the optic was previously used on that rifle. More torque on the attaching screw will do nothing but break it, and the dent still has to be found and removed. Often it is not very noticeable. Some people will cry, “But it is supposed to be hard aluminum!” True, and oak is hard wood, but it is still wood! Such is the price we pay for progress.