Rifle Scopes  ARC M10 Scope Ring Issue

Fire4EffectCA

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I thought I would give the ARC M10 rings a shot after all the praise I have heard here. I have used Knights, Badger, Warne and Bobro mounts over the last 30 years. I am using the ARC M10 rings to mount a Nightforce 2.5-10 x 42 scope on a Daniel Defense MK 12 .

When I follow the instructions I find that the scope will not turn with light resistance with the clamshells open. It feels like the scope tube is being pinched in the rings and I have to raise the scope tube slightly to rotate the scope to orientate the reticle. Light marks are also left on the right side of the scope body, but they can be removed. If I loosen the rail clamp screws on both rings the scope will move freely. If I tighten one ring rail clamp screw the scope will move freely. If I tighten both rail clamp screws the scope seizes up.

To verify that the rail on the rifle is straight I mounted an old pair of Knights SR-25 steel rings and tightened both rail cross bolts and the scope moved freely.

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Has anyone had an issue like this? I am tempted to return the rings and go back to one of my old standbys. I don’t want to permanently mark the new scope body.
 

kthomas

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That doesn't sound right. I have multiple sets of ARC M10 rings, and the scopes all move freely in all directions with the clamshell open. There's no "pinching" or any real resistance of any kind.

Are you sure you aren't trying to put a 34mm scope in 30mm rings? Perhaps you ordered the wrong set of rings, or the wrong set of rings was shipped out by accident? I would double and triple check the packaging that the ARC M10 rings came in, perhaps take a micrometer and measure the ID of the rings.

ARC's are great rings, they are my favorite, but something isn't right here.
 

Steel head

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    As above scope should move freely
    I’d try resetting them on the base and make sure it’s all clean.
    I just put a new set o half an hour ago.
    My favorite rings
    Ring size is stamped on it and ring size+ rise on the base.
     
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    Dthomas3523

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    Try it on another rail. If the binding happens when the rings are clamped to the rail, that leads me to believe the rings aren’t aligned when secured to the rail.

    Rail might be the problem or one of the rings is out if spec.
     
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    kthomas

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    Try it on another rail. If the binding happens when the rings are clamped to the rail, that leads me to believe the rings aren’t aligned when secured to the rail.

    Rail might be the problem or one of the rings is out if spec.

    This makes sense. Missed the part about it only moving freely when the rings are tightened down to the rail.
     
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    Fire4EffectCA

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    I have a complete new LMT MWS upper I built up and just tried the ARC M10 rings on it. It did the same thing. Looks like it's the rings.
     

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    Dthomas3523

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    I was able to create the issue you are describing when the top narrow part of the ring clamp was not inside the slot properly.

    If you have double checked that it is clamping into that slot correctly, send them back for a replacement.

    When it didn’t engage correctly, I dropped my optic in and could feel it snug into rings and wouldn’t turn. Something is causing a mis alignment.
     

    Fire4EffectCA

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    This makes sense. Missed the part about it only moving freely when the rings are tightened down to the rail.

    Actually the scope only moves freely when the rail clamp screws are loose. The scope is pinched when both are tightened.
     

    Fire4EffectCA

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    I was able to create the issue you are describing when the top narrow part of the ring clamp was not inside the slot properly.

    If you have double checked that it is clamping into that slot correctly, send them back for a replacement.

    When it didn’t engage correctly, I dropped my optic in and could feel it snug into rings and wouldn’t turn. Something is causing a mis alignment.


    I can't image anyone actually doing that.
     

    Fire4EffectCA

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    Looks like I need to return these rings. I think I will stick with a one piece mount like Bobro.
     

    Jerry V

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    I just installed my first set of ARC M10 rings this weekend. 35MM. Could not have been more impressed with fit and finish. Scope moved freely with clams open and still rotated smoothly with clams closed and bolt threads just engaging. Mounted a Leupold MK5 in them . torqued down with no movement or rotation. I'm a fan!!
     
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    Fire4EffectCA

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    I just installed my first set of ARC M10 rings this weekend. 35MM. Could not have been more impressed with fit and finish. Scope moved freely with clams open and still rotated smoothly with clams closed and bolt threads just engaging. Mounted a Leupold MK5 in them . torqued down with no movement or rotation. I'm a fan!!


    That's what I wanted to hear that the scope tube should move freely with the clamshells open. I measured the tube diameter on the Nightforce scope I was trying to mount and it was dead on at 30mm. I guess I could try one more rail on a third rifle, but it is unlikely I have two high end rifles with bad rails.
     

    Jerry V

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    One additional thing. I did not torque any of the screws both rail and tube until I had everything set up. All progressed from threaded, to hand tight, to torqued to 52in lbs as I made final adjustments. Are you setting to 50+ in lbs on rail before putting the tube in the open clams? Sounds like that could lead to slight movement that could cause binding.
     

    Dthomas3523

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    One additional thing. I did not torque any of the screws both rail and tube until I had everything set up. All progressed from threaded, to hand tight, to torqued to 52in lbs as I made final adjustments. Are you setting to 50+ in lbs on rail before putting the tube in the open clams? Sounds like that could lead to slight movement that could cause binding.

    You should be clamping the rings down to the rail first. This is the only way to ensure the lugs are properly engaged. It also ensures the best return to zero when taking off and replacing.

    There should be no reason putting them on the rail first causes the binding.

    This is either:

    User error
    Mismatched rings (got one slightly taller or shorter)
    Something out of spec
     

    karagias

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    Threads like this are annoying but they do offer an opportunity to set the record straight.

    First and most importantly, know the follow:

    Attaching a scope to a rifle in a way that can resist the forces of recoil without slippage will deform your scope.

    I make that assertion assuming the scope is constructed from aluminum and that it has a smooth, hollow, and cylindrical interface around which we will install a clamp for the purpose of securing the scope to a rifle.

    It is not uncommon for a rifle to accelerate at 100, 200, or even 300 g’s during recoil. If your scope weighs about two pounds and the rifle accelerates at 200 g’s, then the rings must clamp tightly enough to impart a friction force of 400 pounds during recoil to prevent slippage. Assuming a coefficient of friction of 0.3 for anodized aluminum against anodized aluminum, we must apply a force to the scope tube of at least 1333 pounds, or 667 pounds per ring. That is a lot force and it will deform the shit out of your scope tube, regardless of how much money you spent on it. Furthermore, it will result in a slight misalignment of the ocular and objective lenses because we can not squeeze the scope in a way that is perfectly axisymmetric.

    In short, scope rings, ours and everyone else’s included, seemingly do terrible things to your scope. But, none of that really matters. Years ago, I discussed this matter with an extremely well qualified engineer from Hensoldt and he concluded what reality had already demonstrated a million or more times over. It does not matter. And apart from designing scopes with a dedicated mounting interfaces (which has been done) there is nothing that can be done about this because the solid materials our universe makes available to us for making scopes, rings, and nearly everything else are all elastic.

    So, regarding the practicalities of mountings scopes to rifles, do the following.
    • Place rings on rail, gently biased forward in the recoil slots and snug the rail clamp screws, just a little bit.
    • Place scope in rings and snug the scope clamp screws, just a little bit.
    • Rotate scope to align reticle.
    • Tighten scope clamp screws.
    • Tighten rail clamp screws.
    • Go shoot and be happy.
    Any wish for perfect alignment during installation is meaningless because once you tighten the screws, your perfect pre-tightened alignment goes right out the window. That’s reality no matter what you read on the internet or what your gunsmith is selling to you or what Tinkerbelle may be whispering in your ear.

    All that said, it is worth telling you a little bit about how we make our rings and the material from which they and your rifle’s upper are made. The rail interface and the scope bore for the rings are machined in the same setup, so we are working within the limits of tool deflection and machine repeatability. The scope bore is cut using a polycrystalline diamond edge that essentially never wears out. Pretty amazing but diamond is hard, and aluminum is soft. The rail clamp portion of each ring is certainly flexible and when you tighten the rail clamp screw, you are effectively driving a wedge (the Pic rail of your rifle) into the rail clamp. It is practically impossible to tighten the rail clamp screws so that both rings will deflect in exactly the same way. Moreover, the desire to do such a thing knowing what you now know about the elastic nature of solid materials in this universe is indicative of mental illness. (I’m assuming you’ve read everything that came before that last sentence and I'm trying to keep it lighthearted.) That said, steel rings will undergo less rail clamp deflection than aluminum rings because steel is three times stiffer than aluminum. I don’t mind the flexibility in the aluminum rail clamp because flexible bolted connections are pretty good at staying tight which is a desirable characteristic in a scope ring.

    Also, apart from designing the scope clamp portion or our ring in a way that nearly eliminates annoying scope rotation when tightening the scope clamp screw, we make no effort to enhance the customer’s scope mounting experience. It does not get any easier than what we currently offer.

    Regarding the straightness of your rifles rail, again, it does not really matter. We and all other ring and one-piece mount manufacturer’s are going to bend your scope after the screws have been tightened, whether you like it or not. But your rifle’s upper is likely made from 7075 aluminum. Good stuff, to be sure, and among its many available tempers are T735XX and T65XX, the latter undergoing a stress relieving operation by stretching. This can be important for some structural parts such as AR uppers because after machining has been completed, we want our parts to be shaped as we designed them. We never really get that, but we get close enough. So your rail isn’t perfectly straight, none of them are, but it is extremely likely that it is more than straight enough.

    Opting for an attempt at kindness that conveys truth instead of politeness, on behalf of American Rifle Company and presumptuously all other manufactures in our industry, stop fussing over shit that does not matter. We are all working on producing stuff that we hope will make you happy and offering it to you for a fair price. Just shoot and be happy.

    Ted
     
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    Jerry V

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    Thanks Ted for a dose of reality. We all strive for perfection but " A man has to know his limitations". Super happy with your products!!
     

    karagias

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    Here is something else worth sharing. We also make titanium rings that cost about $1000 per pair and which have receiver and scope interfaces cut using a wire EDM. They are designed to directly engage the dovetail machined into our Mausingfield hunting actions. The rail is not required. The Mausingfield receiver is machined in the hardened condition so its dovetail interface is about as straight as it gets. Now one would think that with that arrangement, loosening the dovetail clamping screws on the rings would enable one to slide the scope and ring assembly off the receiver without resistance. But that is not the case. Even when tightening those rings around the scope, the resulting deformation misaligns the rail clamps enough to be easily felt when removing or reinstalling the scope from the receiver. But again, that OK.

    Ted
     

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    Jumper

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    Nice write up Ted. I'm a little wiser for having read it. Since my M10 scope rings and Archimedes action shipped yesterday I feel more than fine taking up some more of your time by asking a scope mounting question (i.e -screw all your other customers, my stuff is enroute 😁). Concerning scope tube deformation by the rings; would using a chemical bonding compound like one of LocTites's products, be advisable? It seems like it would be good insurance and compensate for any scope-ring mating imperfections? It would make unmounting messier but it wouldn't be permanent like epoxy bedding. Just curious about your opinion if you have one.
     

    karagias

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    I used to favor the use of rosin or even adhesives which can be messy thinking that less clamping force would be better so long as the scopes didn't slip in the rings. But scope mounting as we all know it has been working pretty well for a long time so unless you're shooting a light weight big bore with a heavy scope, I wouldn't fuss with it. That said, Loctite makes good stuff and if you can use it without making a mess, well then why not. It's cheap insurance.

    Ted
     
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    Halfmad

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    I think this information should get stickied somewhere. I feel like I learned something today.
     

    Gil P.

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    @Fire4EffectCA , did you ever mount the scope in the ARC rings?

    Ive never had a set of rings that didn't leave ring marks. I know it sucks but if you never take your rings off, you'll never see them.
     

    Quarter Horse

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    This post is indicative of the reason I read threads that are not necessarily of particular interest to me at any given time. You never know when you'll find a nugget in a pile of gravel. I'm not implying that other posts were gravel. It was all good info. Ted's post was interesting in that it explained technical aspects. Then he assesses the physics against real world results, implies a reason for the difference, provides a brief six point tutorial and tells us to drive on.

    My experience has been problems in the interface between scope and rifle are much more likely found in the rifle rather than rings and bases. I've had several rifles over the years where the height of the action bridges and/or the bridges were out of round. Thus the need to bed bases or rails. I haven't had it happen that I realized that the mounting holes were out of alignment but it is often reported.

    @Fire4EffectCA , did you ever mount the scope in the ARC rings?

    Ive never had a set of rings that didn't leave ring marks. I know it sucks but if you never take your rings off, you'll never see them.


    One of the benefits I've found from the use of rosin is protection of the scope tube from ring marks. I've been using rosin for about five years and have mounted and switched ten to twenty times. I ordered it on a Midway order and ended up with enough. for fifteen other guys. I put what I use in a small pill jar that resides on the bench with alcohol swabs and Qtips. Apply with Qtips and prep and cleanup with alcohol swabs. No slippage and no ring marks........Yet.
     
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    Fire4EffectCA

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    @Fire4EffectCA , did you ever mount the scope in the ARC rings?

    I was never able to mount the scope in the ARC rings. I returned the rings to the dealer. They were digging in to the scope tube like a pair of channellocks. Check out how the 30mm ARC M10 rings would not seat a 30mm lapping bar.

    xlarge.jpg
     

    Fire4EffectCA

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    Gil P.

    I have had good success with not marring scopes with rings. I just moved an old Leupold Mark 4 today from one rifle to put it on an old Colt Delta HBAR. I took off the Colt Delta HBAR buttstock and added a Magpul PRS stock so I could extend the stock and add a monopod. I had an old set of Badger low rings put away from a rifle I sold a while back and these were the perfect height for this application. I secured them to the ARMS mount on the scope carry handle. I always use a lapping bar to align scope rings before torqueing the crossbolts. This Mark 4 has been mounted on different rifles several times and there are no ring marks.

    I also want to mention that the Leupold Mark 4 floated in the badger rings like it was on oil bearings even with the top rings loosely secured.

    xlarge.jpg
     

    Gil P.

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    I was never able to mount the scope in the ARC rings. I returned the rings to the dealer. They were digging in to the scope tube like a pair of channellocks. Check out how the 30mm ARC M10 rings would not seat a 30mm lapping bar.

    xlarge.jpg
    That doesn't look good.
    I'm returning a pair of Nightforce x-treme rings that's put some small indents on my M7Xi. I've never had a problem with any other high end rings. I'm interested to see if there is anything wrong with them.