Rifle Scopes ARC Rings & Kahles
- Thread starter Winny94
- Start date
Short answer:
You’ll be fine. Basically, the torque values that everyone harps about for not damaging scopes? It’s completely irrelevant for these rings. Follow the ARC recommendation, and don’t listen to any advice on mechanics from people who don’t understand that torque and screw size are related.
Longer answer:
Torque equals nut factor (friction coefficient in the threads) times bolt diameter times preload, so preload (boiling down to clamp force on the scope) equals torque divided by nut factor divided by bolt diameter. (Plus some fudge factors for various other things. It’s messy.)
You care about preload and ring clamp area for telling whether you will damage a scope. You really care about preload and interface friction to determine whether your scope will slide. If the ring area is comparable, and the preload is comparable, the scope will be fine.
The ARC rings have a substantially larger screw than anyone else on the market, so need substantially higher torque than anything on the market to hold the scope just as well. However, larger fasteners and higher torques are also more consistent, so the preload spread might be +/- 23% instead of +/- 50%. (Yes, those are actual values I’ve measured in my professional life.)
This means that you can apply still more torque, bringing up the minimum clamping preload (how well the scope is held), without exceeding a maximum clamping preload (how much the scope is crushed).
You’ll be fine. Basically, the torque values that everyone harps about for not damaging scopes? It’s completely irrelevant for these rings. Follow the ARC recommendation, and don’t listen to any advice on mechanics from people who don’t understand that torque and screw size are related.
Longer answer:
Torque equals nut factor (friction coefficient in the threads) times bolt diameter times preload, so preload (boiling down to clamp force on the scope) equals torque divided by nut factor divided by bolt diameter. (Plus some fudge factors for various other things. It’s messy.)
You care about preload and ring clamp area for telling whether you will damage a scope. You really care about preload and interface friction to determine whether your scope will slide. If the ring area is comparable, and the preload is comparable, the scope will be fine.
The ARC rings have a substantially larger screw than anyone else on the market, so need substantially higher torque than anything on the market to hold the scope just as well. However, larger fasteners and higher torques are also more consistent, so the preload spread might be +/- 23% instead of +/- 50%. (Yes, those are actual values I’ve measured in my professional life.)
This means that you can apply still more torque, bringing up the minimum clamping preload (how well the scope is held), without exceeding a maximum clamping preload (how much the scope is crushed).
