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Posted: 5/31/2008 2:46:51 PM EDT
| Is there any trick to installing a rifle scope? Ive heard you are supposed to shim it into calibration before using the actual turrets? Is this true? How's that done? |
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Man, I'm drawing a blank on some websites for you to read about mounting. The first one that comes to mind is Ken Marsh's site. He has pictures, and he's a very good writer. There's a number of others that are also good. Mounting is tricky because nothing is perfect, not the mounting base, not the rings, not the erector tube location in the scope and not the tapped holes in the receiver. The need for shimming is to compensate for the fact that the base is warping for some reason. Then lapping the rings is to make sure that both rings will have the exact same center. That makes sure that the tube won't be bent. Bending the tube forces you to use more internal adjustment, plus if it's bent good enough (like about .04 inch or more) the erector tube will probably be hitting the inside of the main tube every recoil event. That causes an early service life. Do some googling to find the sites and read about the process. There are tools to help, both Brownells and Midway USA sell them, and if you're interested in mounting your own scope, I would recommend getting some of the tools to do the job properly. 55% to 60% of the returns I have seen have bent tubes. It's the number one reason for early service life for all scope makers. |
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I wouldn't think it would be any different except that the rings are integrated to the base, and bad alignment is less of a concern (unless the base gets warped for some reason.) I went to the LaRue site earlier to see if they had on-line instructions. They don't, but you could leave a message for them in the Industry Forum. One important thing you want to do is to make sure that the scope you're mounting is at its mechanical center. This means that the adjusting screws are each set at the half way point of their travel. It's accomplished by first noting how much MOA is there per click of the screw, and then (this is my preferred method) turning the screw counter-clockwise until you get to the end of its travel (don't force it.) Next turn the screw clockwise counting both revolutions and then individual clicks as you near the end of the screw's travel. Divide this result by two and then turn counter-clockwise again until you get to the above result. Then repeat for the other adjusting screw. Don't worry if the number of clicks between the two adjusting screws are equal. They rarely are. However, if they are off by a significant amount, I would either contact the company you bought it from or simply return it for a replacement. The reason for this is because no scope is assembled perfectly. They are assembled to a tolerance for specific reasons. Locating the erector tube is quite difficult and every .001 inch off roughly equates to an MOA at 100 yards. So finding the center of a specific scope helps you out by putting the erector in the center of the main tube as well as it can be placed. I would also keep in mind that if it takes like 10 MOA per screw to bore sight it with a collimator, you might want to recheck everything by starting over. The reason is because that's going to be a big chunk of the internal adjustment used that is controlled by the spring. For example, a typical mid range priced quality general purpose hunting scope will have about 20 MOA from center for Windage controlled, and 25 MOA Up and 20 MOA down (Elevation) controlled by the spring. Sure there are more going to be plenty more clicks, and some individual scopes may be able to accurately control them, but the scope wasn't designed for that. So, you're pretty limited to what is controllable to get the best performance out of the scope. Now for a Night Force, I don't know what their specs are, but when you buy a Night Force, you're paying extra for the mechanical abilities of the scope and not necessarily for an "outstanding" optical system. (They only multi-coat their lenses instead of FMCing them.) But still, as good as the mechanical abilities of a Night Force scope are, you still want to keep the erector tube in the center of the main tube as much as possible. This will give the scope the best chance for a long service life. |
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Shimming is more of an issue on traditional rifles that don't always have a built-in optics mount platform, and there can be tolerance differences between the receiver and mounts/rings. For quality AR gear, the receiver's Picatinny rail and mount should hold tolerances close enough that you can zero with the turrets, no problem. If you have to shim with an AR, it indicates either the upper or the mount are out of spec (not a common problem on LaRue mounts). Just mount it up, put the mount on the upper, boresight, and tweak it in with ammo. |
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