The Accurate Reloading Forums THE ACCURATE RELOADING.COM FORUMS Guns, Politics, Gunsmithing & Reloading Optics Shimming a rifle scope for long-rangeGo | New | Find | Notify | Tools | Reply | |
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| One of Us |
Hi! I have a rifle scope on a Sako 85 that needs about 20 MOA shift, to properly utilize the full range of adjustment for 800-1000 yard shooting. I have already purchased and mounted scope rings (Leupold QRW and Dovetail-to-Weaver Rail adapters). What is the preferred shim method that will allow me to continue to use these rings? I was thinking of using thin strips of either 35mm negative plastic or aluminum soda can... is there something that would work better? My calculations show that I will need approx. 0.020" of upward shift on the rear scope base, and 0.001" of upward shift at the rear part of the front scope ring (which seems negligible enough that I think I'll just skip that part...) Any thoughts or comments? Thanks! | ||
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A friend of mine uses strips of metal soda cans and is quite satisfied. André DRSS --------- 3 shots do not make a group, they show a point of aim or impact. 5 shots are a group. | |||
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I have used simple strips of aluminum foil in the past. Any similar thin metal will work. | |||
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| one of us |
Pieces of aluminum soda can measure about 0.004" thick. If I recall correctly, each 0.001" shim added gives 1MOA at 100yds. So, I'm guessing you'll need 5 pieces of soda can. Only problem is that you start to bind the scope with that much shim. Best option is to move to a 20MOA picatinny rail with rings or the Burris Signature rings with inserts. | |||
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Brownell and Midway has shims...both plastic and metal that are cut to fit standard mount blocks. I've used them both plus brass or steel feeler gauge shim stock available through several industrial catalogs like J&L, MSC or KBC or 20# to 60# bond printer paper or card stock... whatever thickness I happen to need....Soda cans work as well as plain old scratch pad paper...anything that doesn't compress much and can be cut easily. A little dab of clear finger nail varnish, spar varnish, polyurethane, paper glue etc, will seal and harden the paper plus glue it to the receiver and mount block well enough to keep it stuck under recoil but allow easy removal if so desired. So will blue locktite...let your imagination run free.   Old "Rule of thumb" for calculating sight changes...0.001" equals 1" change at 100 yds. It seems to work well for me.  'Njoy | |||
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I was having the same problem with my Tikka rings. I tried to shim them on a 300wsm but I couldn't get the rings to stay in place and handle the recoil with only 2 or 3 pieces of pop can. I switched over and use the Burris signiture rings now and I use the +20 and it gave me a 15 MOA increase in range. | |||
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If shimming puts the front and rear rings out of alignment, the scope tube will be stressed, bent. Don | |||
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Don,
Yes... I was worried about this as well, which is why I did the trig calculations to see how much I needed to also shim the rear-portion of the FRONT scope ring. I came up with a figure in the neighborhood of 0.001" - which any machinist will tell you is completely NEGLIGIBLE in terms of bending a 6" long piece of tubing (or any other shape...). I think, in fact, that the scope mounts and scope itself flex more than that during "normal" installation due to imperfect alignment. Thanks! | |||
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That's why you are supposed to either lap your rings, or ream them for perfect alignment. There's no excuse for mounting a scope in rings that are not perfectly aligned. | |||
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Seems to me that the afformentioned 20 MOA rail made specifically for this purpose is the only suitable answer. Why risk damaging your scope to save a small amount of $$$? -+-+- "If someone has a gun and is trying to kill you, it would be reasonable to shoot back with your own gun." - The Dalai Lama | |||
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Amen. | |||
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| One of Us |
Hello! To the previous two posters: My choice to use the Burris "Weaver Conversion" ring base and Leupold QRW rings has NOTHING to do with saving money... in fact it is a rather expensive (over $120) way to go! The reasons I'm attempting to use that base/ring combination are: (a) I can swap different scopes easily on the rifle, (b) Maintain a reasonable zero when doing so, (c) Easily remove the scope when cleaning or otherwise working on the rifle, and (d) quickly remove a broken scope in the field if necessary. I stated in the original post that I was looking for the right way to shim this scope/ring combination - NOT looking for all sorts of "pet" scope rings that other people like for their own reasons. I was ESPECIALLY not asking for criticism of the economics of my decision - just input on the RIGHT way to go about this task given the selected components. Please... if you can't say anything other than "use brand X rings instead" or tell me how I'm trying to just "save a little money" by using one of the most expensive quick detach systems available (Huh?), please refrain from posting altogether. For those who care, I've since figured out how to properly go about solving this problem - I had my weaver base custom machined on a mill (with different height angled weaver slots between the two bases), in order to use the QRW rings as intended and not torque the scope. First ever group with the rifle was 3 shots in a 0.2" hole at 100 yards with FACTORY ammo - so I guess SAKO, Nikon, and my optical mounting aren't doing things ALL wrong!  Thanks! | |||
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Well, If your not going to be incredibly offended I'd venture to ask how accurately the scope switching system is for you? I've seen guys preparing for elk hunts and switch scopes and bore sighters expecting to make shots at 500 yards. Just curious. | |||
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Hello!
Not offended at all! I've used the Leupold QRW rings on another rifle (.243 Win.) and have found that removing/replacing a scope or switching scopes, I experience about 0.5 - 0.75 MOA of shift in zero... but if I take special care to try and get the "tighness" of the locking levers consistent, I can do even better than that. They really are great rings - sturdy and repeatable. Thanks for asking! | |||
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I have to admit to being a bit miffed that you are so sensitive and my answer got you so riled. My post was simple AND provides the answer you're looking for. The 20 MOA base will give you the extra elevation you need and with good quick-detach rings like the Leupold QWR you will get acceptable repeatability. All this without monkeying around with something that wasn't specifically designed for your purpose AND economical. I now realize you don't care about economy but it's just an unfortunate (for you only) side effect! If you're only looking for people to answer if they like your idea then say so and the rest of us will refrain. Oh, and don't be so pissy. -+-+- "If someone has a gun and is trying to kill you, it would be reasonable to shoot back with your own gun." - The Dalai Lama | |||
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Mr. Slug, Perhaps I was overly sensitive, but it was YOU who (falsely) claimed that I was going to "damage a scope just to save a little $$$" or something to that effect. I felt that you were taking my original post in a way that it was never meant to be taken, and when Mr. DMB posted "Amen" to your post, I felt things were getting out of hand. Never ONCE did I claim to be trying to "save a little money", only claiming to want to approach the problem the right way and find a workable solution given the components I'd carefully selected for my intended use. It is I, not yourself, who has a right to be "miffed" about this whole thing - you didn't even bother to ascertain my intentions and understand what I was trying to accomplish before throwing in a snide comment about how 20MOA rings were the only suitable answer, and make a thinly veiled comment about my penny pinching. BTW, who in their right mind would buy a $1,500 rifle, top it with a $450 scope, then try to "save a little money" on scope rings? The whole idea flies in the face of common sense! Thanks for your feedback, I'm hoping this won't degenerate further - this post is an attempt to try and give you my side of things and explain why I replied in a "pissy" manner. | |||
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"BTW, who in their right mind would buy a $1,500 rifle, top it with a $450 scope, then try to "save a little money" on scope rings? The whole idea flies in the face of common sense!" That was exactly my point. Please take this as a genuine piece of constructive, sincere, advice: Don't take anything said here too seriously! My first post here wasn't meant to be inflammatory and I think you took it too seriously. I was simply stating MY OPINION that the specific bases made for this purpose are the only way to go. You asked for opinions and that's what you got. I've got no beef with you. -+-+- "If someone has a gun and is trying to kill you, it would be reasonable to shoot back with your own gun." - The Dalai Lama | |||
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Hello again, Mr. Slug - No worries, let's move on to more productive discussions. I don't have any beef with you either... Thanks again for the replies! | |||
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A set of Burris Signature rings with the maximum + inserts in the rear and - in the front can buy you almost 20 MOA. cheap, strong simple | |||
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The Accurate Reloading Forums THE ACCURATE RELOADING.COM FORUMS Guns, Politics, Gunsmithing & Reloading Optics Shimming a rifle scope for long-range
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