AR15.Com Archives
 Proper scope mounting
dallas77  [Member]
12/30/2008 5:13:55 AM EST
I looked in this forum didn't find much.I would like to know the right steps to properly mount a scope.I would like to know about aligning scope with the boreThanks for any input

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skipsan  [Member]
12/30/2008 5:51:46 AM EST
I assume you're talking about intial bore sighting of a scope, without actually firing the weapon. I also assume you're talking about an AR-type rifle/carbine.

My method isn't very sophisticated but it's worked so far on several rifles.

Either remove the "upper" or if that's not feasible, open the rifle and firmly cradle the open rifle so that the barrel is pointing safely downrange toward a "target" or some distinctive object about 25m distant. There's nothing floppier and harder to handle than an open AR so make sure that everythng is secure and not going to fall or tip over. I use a little link between the upper and lower to firmly hold them open, but no-one seems to share my preference for this link.

Having either seperated the upper from the lower and "aimed" the upper at a target or distinctive object down range (out of sight of the neighbors), or if the upper can't be removed the open, rifle is firmly cradled in the open positin and pointed down range, remove the bolt carrier group from the upper. You can now "eyeball" down the barrel and by "shimming" the upper/rifle in its holding system you can get the barrel pointed at your "object of interest" down range. I hang a paper target on the block fence, but any distinct object will suffice.

Assuming you have installed the scope on the rifle, and that the eye relief is acceptable, sight through the scope. It probably isn't pointing exactly at the same point that you've eyeball-sighted the barrel at. As carefull as possible (so you wont jiggle the rifle) adjust the elevation and windage of the scope so that the scope is pointed exactly at the same thing. Recheck the boresight down the barrel to make sure it hasn't shifted––adjust as necessary. Recheck the line-of-sight of the scope to verify it still points at the point of interest down range––the same as the boresight.

Assuming that the scope, and barrel eyeball boresight now point at the same object down range, the rifle is now boresighted at that range, and you can go the range and start shooting at that approximate distance (the one you boresighted to) with confidence that you will at least "hit the paper" and proceed with normally sighting in from there at whatever range you choose.

As far as actually afixing the scope to the rifle, with the scope mounted loosely in the mounts, get the eye relief distance established to your preference. That is, move the scope back and forth until the sight picture is complete with your headbone in the correct shooting position.

With that done, tighten the ring screws sequentially, like you would tighten lug bolts on a car tire. Make sure that the gaps where the rings come together are approximately equal in size. Most folks use blue loctite at this point, but you may want to forego that until you've been through the boresighting process once successfully and feel confident you're where you want to be. THEN, go back and retighten eveything down with the Loctite.
FreeFloater  [Member]
12/30/2008 6:16:12 AM EST
I am contemplating buying a boresight laser. The method described above will work out OK...but can be sped up considerably with the use of a $40 laser that is designed to go in your bore.

My other use for the guide is when sighting in a laser. I think I want the laser to run parallel to the barrel at all times rather than adjusting for height or wind to make it impact at the bullet site. To make this really accurate, a boresight laser would be very helpful.

In fact, all sighting can be made easier with the laser...but as mentioned, you can skip that if you want to...and do it a different way. Keep in mind that the boresight is only the first step. Tweaking will need to be done afterwards to get the bullet trajectory worked out, but windage should be more or less dealt with using the boresight.
Fbuckshot  [Member]
12/30/2008 6:45:24 AM EST
Simple really. Buy the proper base and rings for your gun and scope. Degrease the mounting screws and holes on the receiver. Put a little tiny bit of blue lock-tite on the screws and equally torque them down. You can go by feel or buy something like a F.A.T. wrench if you want. Attach the rings to the base. Methods vary depending on which ring/base set up you buy. Just follow the instructions that come with the base and rings and use common sense. Put the scope loosely in the rings and start checking eye relief. Don't use lock-tite on the ring screws. With the scope on it's lowest setting, close your eyes and mount the gun. When you can open your eyes and see a clean, unobstructed sight picture through the scope, you have established proper eye relief. Now square the reticle to the gun. I just put my gun on a flat surface and look through the scope with out touching the gun. Of course, there's tools you can buy to help with this part of the job too. Take your time and get this right. HINT - Most folks mount their gun slightly canted. Do not square the reticle to a canted hold, you'll make yourself crazy because your windage/elevation adjustments won't work right if you do. Most quality scopes come with the reticle centered within the max windage/elevation adjustments. When in doubt, carefully turn the knobs from stop to stop (don't force anything here), and count the total number of clicks or rotations, divide in half, and turn in that adjustment. You're ready to sight in. Take the ammo you're going to use, a solid rest, and a friend to the range. Put up a good target (I like Redfield Precision Sight-In Targets) at 25 or 50 yards. Shoot for the center of the target. Reestablish the aim point on target center again and hold the gun absolutely still, it must not move at all. Have your friend dial in windage and elevation adjustments until the reticle moves to and covers the bullet impact hole. You now sighted in at about "minute of pie plate." You can adjust for your preferred distance now.

There's some fine tools available for precision scope mounting. Very cool and I wouldn't mind owning them. You can get stuff to lap you rings, etc. That's scope mounting at the nth degree and cost a little more than most folks want to spend for mounting one or two scopes. What I described above has worked for me, my family, and my friends for years with lots of guns.