Can you convert "45lb lbs" to ugga-duggas? That's the only torque spec that I understand.
Doing my own engineering over here, I would like to note that the 45 in-lb spec (which converts over to 5 N-m) is about 30% lower than the spec for a M5 bolt of Grade 8.8 and a full 50% lower than that of a Grade 10.9. This sort of under-specifying of fastener torque possibly indicates that the mechanical design of the mount is already inadequate to handle the potential clamp load of the fastener, or at the very least suggests that broad margin has been provided to minimized the likelihood of broken fasteners during installation at the expense of performance. Either way, the shit shouldn't be breaking even with a torque wrench of poor quality, and if it's user error from incorrect units as you suggest then we should be seeing the fastener yield which does not appear to be the case.
I've got one Spuhr because it was the only option that provided the desired angle to optimize scope travel on that particular rifle. It's worked fine and I'll continue to use it, but future purchases will Badger or Nightforce Unimounts because they have no apparent issues accepting reasonable torque values for the provided fasteners.
When someone was saying the 45 in-lb spec is too much I was going to suggest to look up the recommended torque specs for unplated, plated, and black oxide grade 10.9 low head M5 socket head cap screws and note that Spuhr's specified 45 in-lb is actually on the conservative side per the various hardware manufacturers torque guidelines, but I see you've already beaten me to it. Don't forget though Spuhr uses low head fasteners on the clamp bar which have a much lower specified torque than regular height head socket head bolts (which I think you referenced)-- but 45 in-lb is still on the conservative side for a low head 10.9 M5 unless you slather it in grease or anti seize and significantly change the k factor from the manufacturers testing charts.
You want enough elastic deformation in the fastener when tightened to "spring load" the joint, and higher strength/grade screws will require a higher torque and create a higher clamp load to achieve that. If spuhr wants to reduce the clamp load and stress on the clamp bar but still have adequate elastic deformation of the fastener they could switch to grade 5.8, 8.8, or 9.8 or even drop the fasteners a size down to M4 and reduce the torque spec accordingly. You'll then have adequate stretch on the bolt to tension the joint to absorb shocks and resist loosening but with a reduced overall clamp load on the clamp bar. Unfortunately the lower grade fasteners have a lower yield strength so now there's a greater chance of them stretching or breaking if you were to say bang the scope and mount on a barricade or something.
At this point IMO Spuhr might want to consider keeping the grade 10.9 or 12.9 M5 screws and going to a stronger clamp bar material or design (or both)... that would be my suggestion. This problem has persisted for over a decade now through at least 2 and possibly 3 revisions of clamp bar design. It's still not solved, which is why I sold off all my Spuhrs even though I really liked their 45 degree ring split for the great visibility of the turrets (ignoring the other design issue of using flat head screws for the ring caps...)
There would probably be a good market opportunity for third party steel clamp bars, and I'm surprised nobody has made them yet...
This was not always the case, it happened much later, and you can see the side plate changes over time
Adding screws, new side plate designs, the Spuhrs are good, just something changed with them
Been happening for at least a decade, or even longer. My first clamp bar cracked about 8 or 9 years ago, mount was probably a year old at the time. Plenty of posts going back to 2011ish showing cracked clamp bars and even cracked rings. The failures have always been there, it's just as more people started using spuhr you saw an increase in posts about the failures even if the overall failure rate stayed about the same.
The Gen 1 thin clamp bars on the 1.18 high mounts with minimal edge margin to the bolt holes were the worst for cracking in my experience, followed by the thin and tall clamp bars on the Gen 1 cantilever mounts that flexed a ridiculous amount when tightening.
Also, the head OD of the ring screws was reduced and the screw spacing slightly altered for the gen 2 ring caps to leave more material and edge margin around the screw heads as on the Gen 1 the countersinks for the 4x outboard ring screws left only a knife edge of material remaining that acted like a crack propagation point. I haven't seen nearly as many pictures of cracked gen 2 ring caps compared to cracked gen 1 ring caps, but it still happens, although based on pictures the rings fail at a much lower rate than clamp bar failures.
Hmm. I notice you didn’t list NF , ZCO , Geisselle , Badger
If this was still 2001 and we were all still using badger steel rings we'd probably never have threads about ring and mount failures... I'm pretty sure those things are invincible. We'd have lots more threads about lapping and ring marks though, lol
