UM Tikka rings are not recommended for cartridges larger than 7mm PRC?

[Formidilosus]

Yeah, but mine were installed correctly from the start according to the manufacturer. Now they’re not.

Quit covering for their blunder. It’s not a good look.

Are you purposely this obtuse?

No one is covering for anyone- I HAVE ALREADY STATED MULTIPLE TIMES that they ignored the correct specs and testing given them. That has nothing to do with whether there is a real issue with the rings and 7mm mags.


If you spent as much time testing your rings as you do complaining about everything in every thread, you would know if there were an issue or not.

 

[Fowl Play]

Sure. Or maybe the people with collectively several hundred thousand rounds of experience on the rings might have a better idea if there is a real issue when mounted correctly.

Are you torquing the fasteners or doing it by feel?

65 in-lbs is allot of torque for a #8/M4 sized screw. Which is probably why UM is hesitant to spec that. It might take you 65 in-lbs, but your male and female threads might interfere a little more (more friction) and your torque wrench could be on the low end, etc.

Someone with threads that mesh nicely (less friction) and a wrench on the high end is going to strip the head off or strip aluminum threads at 65 in-lbs.

# of turns past snug *might* be more repeatable for a larger percentage of people. UM would have to test that.

For what it’s worth. I did some quick back of the napkin math using some recoil velocity’s off chuck hawks site for some of the stouter calibers. Assuming recoil occurs in 2 milliseconds (?) you can calculate an acceleration to put in a F=ma force equation using those velocities. If you assume a heavier night force optic, DAF of 2x, etc you can get some forces pushing 900lbs for that instantaneous shock load. A properly spec’d shear pin (that is seated properly) can handle that no problem. But that is a tall order for 4x number 8 fasteners to hold with friction. They can do it, but it has to be pushing close to the upper end of their allowables.

Which is why you probably had to torque the bejesus out of them.

 

[nm.otter]

The Sako/Tikka rails are stupid strong. Just to deform the edge you'll need a solid point load impact -- think hitting with ball peen hammer or falling just so on the edge of a sharp rock.

 

[Formidilosus]

Are you torquing the fasteners or doing it by feel?

With a wrench. But I have also just went tight by feel. The head strips before the bolt breaks or the mount gives out- I have done at least a dozen until the head strips. It’s above 80in-lbs that it happens.

65 in-lbs is allot of torque for a #8/M4 sized screw. Which is probably why UM is hesitant to spec that. It might take you 65 in-lbs, but your male and female threads might interfere a little more (more friction) and your torque wrench could be on the low end, etc.

There’s lots of reasons for lots of things. However, they are empirically wrong.

 

[TimberHunter]

Lot of guys saying they know a lot about joints, yet none of them make scope rings…

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[Fowl Play]

There’s lots of reasons for lots of things. However, they are empirically wrong.

I don’t doubt your empirical evidence. I might doubt your torque wrench or sample size

The calcs and assumptions you use for the equations are worst case for everything. Weakest material strengths per specification, worst case tolerances, worst case scenarios, etc. nothing should ever actually stack up this way, but it’s the only way to design something that will not fail across thousands or more units.

I won’t comment more on that as I don’t work for UM and haven’t done in depth calcs like they should. I’ll just say 65 in-lbs is a very high torque spec for that size fastener.

 

[TimberHunter]

I don’t doubt your empirical evidence. I might doubt your torque wrench or sample size

The calcs and assumptions you use for the equations are worst case for everything. Weakest material strengths per specification, worst case tolerances, worst case scenarios, etc. nothing should ever actually stack up this way, but it’s the only way to design something that will not fail across thousands or more units.

I won’t comment more on that as I don’t work for UM and haven’t done in depth calcs like they should. I’ll just say 65 in-lbs is a very high torque spec for that size fastener.

Look man, I don’t know you from Adam. But I know one fact about you, you’re an engineer. We all know you’re an engineer. Hell my work title is an engineer, so I’m not hating because I’m ignorant.

Just let it go man, you told everyone your thoughts on the topic and now you’re arguing with a dude that has put these things through the wringer.

A hard lesson I had to learn myself: What works on paper, doesn’t always work in the real world and vice versus.


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