Friday, February 04, 2005

I was recently was asked about mounting telescopic sights, aka scopes or scope sights. I read a lot of different articles, some more than once, and some maybe 2 or 3 years after first reading them. See a lot of posts on the internet.

I have always been a cheap so-and-so and would not even buy a scope for many years. Didn't like them, didn't need them, and didn't want to spend the money. Then my attitude began to undergo a change as I got older (who's sight doesn't get worse as they get older?) and when I began to feel a need for more precision. I had a couple of .22 rifles on which I mounted a scope sight for the purpose of squirrel hunting and made some really good shots. Then I go into Contenders and they are a natural for mounting scopes easily and maintaining their easy-to-carry characteristics. While I would never want to mount a scope sight on a levergun, most of my contender barrels have one.

Because I'm a cheap so-and-so, it seemed natural that I would mount the scopes myself. Of course, I'm too cheap to get a bore collimator or bore sighter (such as this Leupold Boresighter or this Simmons Boresighter. So, I've had to use a multitude of field expedients.

It is necessary and sometimes difficult is to ensure that the reticule is not canted in relation to the gun bore. I've used levels, plumb lines, the Reticule Leveler and all sorts of other devices and field expedients to correct problems. Sometimes you have to get really creative. However, you must start with the mount which must be of the correct relationship to the bore. Sometimes even the factory will get the D&T wrong (but not that often in my experience). When that happens, some people will quickly resort to shims.

I never use shims if I can help it. Mechanically, they are another very weak link in the physical chain connecting the scope to the mount and mount to rifle. IOW, the shim can actually render the scope to rifle relationship more tenuous than is necessary. MOST (not always) of the time shims are not needed to zero the firearm. MOST scopes have the range of adjustment needed, much more than needed IN MOST CASES. There are cases where the BASE or MOUNT must be shimmed to ensure it is square to the rifle but because of the way bases attach, there isn't nearly the chance for slipping that shimming in the rings might present. If gross off-sets are needed there are rings made with inserts such as the Burris Posi-lin that obviate even a perceived need to shim and also those that provide lateral (windage) adjustment such as the Millet Angle-Locs.

For shim material I particularly don't like the use of cartridge brass because it is tapered. You can't ensure that it isn't tapered because from the head of the case to the case mouth the brass will taper in thickness. Tapered shim material does 2 bad things. One, it makes it extremely difficult to judge the degree of change you'll get when you tighten the work down onto the shim. Two, not all of the shim material will be in contact with both work surfaces which reduces the friction which holds everything in place against recoil.One shim material that is usually consistent in thickness across the shim AND cheap is the side of a soda or beer can (I'm afraid to admit how many BEER can shims I've made! ).

For my scoped guns (which are now all Contenders) I use Weaver mounts and low Weaver rings. I square the reticule using the Reticule Leveler. Weaver rings can easily torque a scope out of square and so I tighten every other ring screw ¼ turn at a time until they are all fully tightened. I might bore sight but often find it a waste of time. I go to the range. I fire one shot on the target. I secure the gun with the crosshair directly on the one bullet hole. I then adjust the sights so that the crosshair is directly over the desired POI. I then fire a single confirmation shot. I've already tested the ammo used and have the supposed ballistic performance to hand. I then shoot to confirm at 25, 50, 100 and 150 yards. I then zero for maximum point blank range. I'm not one to be changing sights of any kind and for the light loads I make up for some rifles, I adjust the load to shoot to the sights albeit at shorter ranges, say 25 yards. This system works for me. If I pay attention to detail, the "chore" goes off without a hitch.

This is not to say that other methods don't result in zeroed guns but this seems so much easier to me. I know because I've tried the method of locking the gun into a vise making sure all is square and level and then using a plumb line on which one lines up the vertical crosshair of the reticule. Too, many steps many interconnecting parts. At each connection a bit more slop or error creeps in. It can be enough to drive anyone crazy.

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