Rifle Scopes Tangent Theta 5-25 and Spuhr

[Smithcollector]

I recently bought a Tangent Theta 525P. My thoughts on the scope itself are further below. I like to use Spuhr unimounts, and planned to swap out a S&B with this new scope.

So when I dropped the TT into the old Spuhr mount and torqued to 20 in/lbs (Spuhr's suggested range is 15-25), the parallax knob was binding - it would freeze up about half-way through its normal range.

At the suggestion of the vendor I reduced the torque value; at 18 in/lbs there was a noticeable drag at the same point in the range, and at 15 in/lbs there was a very slight, maybe noticeable only to me, catch.

The S&B that was in this mount had no issue with 20 in/lbs.

The vendor (who has been fantastic through this entire process) thinks I'll be OK to use 15, since that's within Spuhr's 15-25 spec. I'm a little nervous, the rifle is a AXMC 338, and I don't want any slipping. Am I wrong to think this is a little finicky at this price level?

So any experience with TT and Spuhr? Any thoughts on just using the minimum torque value?

Thanks


BRIEF SCOPE REVIEW:

The glass is fantastic, although to my eyes at 1200 yards it wasn't a significant improvement over the S&B 5-25. The turrets are also fantastic, clean and crisp and much easier to see than either S&B or NF. The parallax adjustment range is much shorter than S&B which I liked. I also liked the locking focus ring, as my S&B always seems to get moved around. The real kicker to this scope is the zeroing feature - rather than fooling around with tiny screws and an Allen wrench you just twist an emedded dial and change the zero. Really slick and well-done, and makes the scope worth the premium on this alone if you switch rifles or barrels

 

[Covertnoob5]

I had my TT at 20in/lbs in a spuhr and era-tac. I did experience slipping with the era-tac even up to 30in/lbs. so I switched to a spuhr no issues. I would definitely talk to TT about it. They have great customer service and pretty quick turn around. I’ve sent 2 back to them.

 

[MACHTECH]

I just mounted a TT 5-25P on my Desert Tech in an ERA-TAC adjustable moa unimount. I torqued the screws to 25 in/lb. like I did on all my others and had the same thing happen. The parallax adjustment locked up solid. I backed it off to 20 and it freed up some, but was still catchy in a couple spots. I then backed them down to 15 in/lb and it freed up totally with no binding at all. Not comfortable with 15 in/lb, I tore it all down and mounted the scope in a tried and true ARC unimount and torqued it to 55 in/lb and tried the dial again. It was still completely free with no sticky spots! I guess it will live it's life in the ARC mount from now on.

 

[bjay]

Hmmm so TT tube is flexing at 30" torque?

 

[koshkin]

Interesting. I had the TT tightened more than that in an Aadmount with no issues.

ILya

 

[Apollo1218]

TT manual says 15 in/lb in bold letters.

 

[Jeffd]

I have 8 TT scopes and have never had this issue?

 

[Renomd]

I got two TTs 5-25 both in spuhr mounts torqued to 20 in lb and have no issues with binding or slipping

 

[FourT6and2]

TT literature says 15 in-lbs. max. If you over-torque the rings, you risk damaging the scope. Have had both of my 525Ps in Seekins rings for a few years with zero issues. 15 in-lbs holds just fine, but I shoot 6.5 Creedmoor, not 338.

 

[patriot07]

I have 8 TT scopes

Are you open to adoption? I'm 33 years old and a little heavy, but not too heavy to bring you a beer whenever you're running low.

 

[Jeffd]

Are you open to adoption? I'm 33 years old and a little heavy, but not too heavy to bring you a beer whenever you're running low.

LMFAO!

 

[Jeffd]

Forget to mention, all in SPUHR mounts

 

[powerspc]

Received my TT525P yesterday and hope to get it mounted today. As stated above the TT User Manual says in bold;

5) Ring cap screws should not be tightened beyond 15 inch-pounds torque.

I'm going to using a Cadex Unitized Scope Ring which recommends 20-25 in-lbs. So is the general consensus that you follow the recommendation of the scope manufacturer versus the mount manufacturer? Any help appreciated!

Scope is going on a Cadex Defence Kraken .338LM

 

[MACHTECH]

I put my S&B 5-25 in the ERA-TAC mount that the TT came out of and torqued it to 25 in/lb and it's fine. Tangent must use a thinner wall tube than Schmidt is the only explanation I can think of.

 

[hk dave]

Odd, I recall reading somewhere that they thickened the tube walls after the Premier fiasco.

I’ve never had a problem with spuhr and the tt combo. I too run 15 in/lbs.

 

[Smithcollector]

I didn't know Premier had a similar issue, but I also didn't realize the TT used any specs from Premier except reticle design.

I'm not an engineer, but it looks like that would be a very easy fix - just make the tube a little thicker.

Maybe I shouldn't be worried about using only 15 in/lbs of torque; I see some here have done so with no problem. It's worrisome to me that this only seems to be a problem with the TT.

 

[MACHTECH]

I think 15 in/lb is fine for most short action calibers. I shoot a lot of 300 Norma mag in my desert tech though and am not comfortable with 15 in/lb holding my scope. I've put around 100 rounds thru the Norma in the last couple days and the ARC mount is holding it firm. The ARC mount at 55 in/lb must put force on the tube in a different way than the ERA-TAC mount.

 

[Rhed]

Have my tt315p on a Spuhr cantilever mount. Locked down to 25 in/lbs. No problems..

 

[kortik]

Received my TT525P yesterday and hope to get it mounted today. As stated above the TT User Manual says in bold;

5) Ring cap screws should not be tightened beyond 15 inch-pounds torque.

I'm going to using a Cadex Unitized Scope Ring which recommends 20-25 in-lbs. So is the general consensus that you follow the recommendation of the scope manufacturer versus the mount manufacturer? Any help appreciated!

Scope is going on a Cadex Defence Kraken .338LM

I was thinking about it as well, which torque spec is most likely makes more sense, the one from the scope maker or the one from the mount/rings maker. Because application of torque "transfers" into creating of two forces, one to actually clamp the scope using a certain surface of contact with rings, and the other to slightly deflect the scope rings, so that scope rings would provide sufficient contact surface with the scope tube (taking most of the clearances out), it looks like using torque spec from mount/rings manufacturer makes more sense.

On the other hand, torque spec from the scope manufacturer may serve as a sort of indication how well the scope tube will take potential deflection from the clamping forces.

For this reason, I do not like to use "beefy" scope rings, as it is difficult to predict how much force (created by torque application) would be required to "wrap" the rings around the scope tube, and how much force would be actually left to clamp the scope. There are, of course, other factors involved, like friction here and there, etc.

In general, my personal approach is to simply select scope/rings combo, which come with either the same or very close torque specs, not to be different from each other by more than just a few inch-lbs.

 

[powerspc]

I’m going to try mine at 15 in-lbs and see how it goes, if .338LM doesn’t rattle it then I figure I’ll be good.

 

[Smithcollector]

I’m going to try mine at 15 in-lbs and see how it goes, if .338LM doesn’t rattle it then I figure I’ll be good.

Please update for your results, my whole thing started by wanting to use the TT on a 338 AXMC

 

[powerspc]

I was thinking about it as well, which torque spec is most likely makes more sense, the one from the scope maker or the one from the mount/rings maker. Because application of torque "transfers" into creating of two forces, one to actually clamp the scope and the other to slightly deflect the scope rings, so that scope rings would provide sufficient contact surface with the scope tube (taking most of the clearances out), it looks like using torque spec from mount/rings manufacturer makes more sense.

On the other hand, torque spec from the scope manufacturer may serve as a sort of indication how well the scope tube will take potential deflection from the clamping forces.

For this reason, I do not like to use "beefy" scope rings, as it is difficult to predict how much force (or torque application) would be required to "wrap" the rings around the scope tube, and how much force would be actually left to clamp the scope. There are, of course, a bunch of other factors involved, like friction here and there, etc.

In general, my personal approach is to simply select scope/rings combo, which come with either the same or very close torque specs, not to be different from each other by more than just a few inch-lbs.

I like your thinking; following that logic and in this case with the TT525P (max 15 in-lbs) what would you use for a mount? Originally I was going Spuhr but thought I would give the Cadex mount (20-25 in-lbs) a whirl; using your method Spuhr wouldn’t have fit the mold either

Please update for your results, my whole thing started by wanting to use the TT on a 338 AXMC

Please update for your results, my whole thing started by wanting to use the TT on a 338 AXMC

Will do; if it ever stops raining. Most likely won’t get back out until next week; I will update though!

 

[kortik]

I like your thinking; following that logic and in this case with the TT525P (max 15 in-lbs) what would you use for a mount? Originally I was going Spuhr but thought I would give the Cadex mount (20-25 in-lbs) a whirl; using your method Spuhr wouldn’t have fit the mold either

Spuhr, w/o doubt, is a high quality scope mount. However, and for my personal taste, it has pretty "beefy" rings, which may have an occasional issue, depending upon combination of tolerances, with easily "wrapping" around the scope tube and closing most of the clearances in the dimensional chain. As a solution, Spuhr sometimes talks about using rosin, and also appears to raise torque specs for rings from original 20 inch-lbs. to 25 inch-lbs. May be I'm reading too much into it, I'm not sure, Spuhr knows better, I guess... For this reason only, I would choose just about any quality rings, which are either relatively flexible (have relief cuts or thin wall for the top rings), or have something like ARC rings construction (hinged rings). However, mount itself should be sufficiently stiff, it will never hurt. These are the general guidelines, which I use, and unfortunately, I will not provide specific recommendations - I've build my own rings and mounts, and for this reason, did not have a chance to evaluate and test any of the available quality rings/mount combos.

 

[powerspc]

Spuhr is, w/o doubt, is a high quality scope mount. However, and for my personal taste, it has pretty "beefy" rings, which may have an occasional issue, depending upon combination of tolerances, with easily "wrapping" around the scope tube and closing most of the clearances in the dimensional chain. As a solution, Spuhr sometimes talks about using rosin, and also appears to raise torque specs for rings from original 20 inch-lbs. to 25 inch-lbs. May be I'm reading too much into it, I'm not sure, Spuhr knows better, I guess... For this reason only, I would choose just about any quality rings, which are either relatively flexible (have relief cuts or thin wall for the top rings), or have something like ARC rings construction (hinged rings). However, mount itself should be sufficiently stiff, it will never hurt. These are the general guidelines, which I use, and unfortunately, I will not provide specific recommendations - I've build my own rings and mounts, and for this reason, did not have a chance to evaluate and test any of the available quality rings/mount combos.

Thanks again, all good stuff. I will try the Cadex mount at 15 in-lbs and report back. Your observations are interesting to me as I had many days when I was pulling this whole kit together where I was kicking myself for not going with Spuhr. Hopefully I’m not reading too much into your post but it seems quite possible I may end up being happy I stayed with the Cadex mount. We shall see....

 

[kortik]

There is one other thing to consider - scope weight. It appears that scope manufacturers give people a "blanket" torque spec value for all of their scopes, regardless of the weight. Say, NightForce says 25 inch-lbs., Vortex says 18 inch-lbs., etc. However, by laws of physics, the lighter the scope, the less clamping force may be required to resist the certain amount of recoil. NF makes both relatively heavy and relatively light weight scopes, but suggests 25 inch-lbs. for all of them. Which makes it easy for them not to confuse people what applies to what, and it makes certain sense. Also tells me that NF scope tubes are pretty strong. In fact, for a relatively light NF scope, say, around 1 lbs. in weight, 25 inch-lbs. may not practically needed, if scope rings, by design, have ability to easily adjust to the actual scope tube size. So, it's all a bit of the black magic here, but it seems to work just fine, at least for me...

Boris
Borka Tools

 

[koshkin]

I am not sure I am on board with your flexible ring theory, but this is not really my field. I have all sorts of problems with rings that flex, no rpoblems whatsoever with the Aadmount that is designed to be very stiff.

ILya

 

[powerspc]

There is one other thing to consider - scope weight. It appears that scope manufacturers give people a "blanket" torque spec value for all of their scopes, regardless of the weight. Say, NightForce says 25 inch-lbs., Vortex says 18 inch-lbs., etc. However, by laws of physics, the lighter the scope, the less clamping force may be required to resist the certain amount of recoil. NF makes both relatively heavy and relatively light weight scopes, but suggests 25 inch-lbs. for all of them. Which makes it easy for them not to confuse people what applies to what, and it makes certain sense. Also tells me that NF scope tubes are pretty strong. In fact, for a relatively light NF scope, say, around 1 lbs. in weight, 25 inch-lbs. may not practically needed, if scope rings, by design, have ability to easily adjust to the actual scope tube size. So, it's all a bit of the black magic here, but it seems to work just fine, at least for me...

Boris
Borka Tools

Or perhaps the other way round as well; the manufacturer of the mount (in this case Cadex) does not know the manufacturer of the scope and certainly not it’s weight. So it may be recommending a torque value at the high end to cover all (most) of the variables across all of the different possible makes and models. If that’s the case then it may be correct to follow the scope makers recommendations for torque values and not the maker of the mount.

 

[kortik]

I am not sure I am on board with your flexible ring theory, but this is not really my field. I have all sorts of problems with rings that flex, no rpoblems whatsoever with the Aadmount that is designed to be very stiff.

ILya

Ilya, good to hear from you.

I will never argue with you, I like and respect you very much. I wish we could meet again and have a couple (or more) shots to celebrate the world of rifle scopes...

When I say "flexible ring", I mean, of course, the metal ring which can deflect enough to closely match the actual scope tube O.D., and not a scope ring that behaves like it's made out of rubber...

 

[kortik]

Or perhaps the other way round as well; the manufacturer of the mount (in this case Cadex) does not know the manufacturer of the scope and certainly not it’s weight. So it may be recommending a torque value at the high end to cover all (most) of the variables across all of the different possible makes and models. If that’s the case then it may be correct to follow the scope makers recommendations for torque values and not the maker of the mount.

As I've mentioned, it is a sort of black magic... Use your own logical thinking to arrive to the right conclusion.

 

[hk dave]

It’s about surface area. A well designed ring design will have maximum surface area touching the scope tube. With more surface area in touch, the less overall in/lb required as tension.

As far as I understand it, there is a second factor. Depending the the size of the bolt and threads, it could potentially require a different in/lb at the bolts. Meaning that 55in/lb could mean the same pressure on the tube as 30in/lb depending on bolt size and thread pitch.

I’m sure an engineer will come around and confirm or correct me.

 

[patriot07]

It’s about surface area. A well designed ring design will have maximum surface area touching the scope tube. With more surface area in touch, the less overall in/lb required as tension.

As far as I understand it, there is a second factor. Depending the the size of the bolt and threads, it could potentially require a different in/lb at the bolts. Meaning that 55in/lb could mean the same pressure on the tube as 30in/lb depending on bolt size and thread pitch.

I’m sure an engineer will come around and confirm or correct me.

Generally speaking, you have to have more torque to produce the same clamp force on a larger diameter fastener. That's why I don't understand scope manufacturers providing a max torque - in theory, they don't have any idea what diameter the screws on the scope mount are.

It's the equivalent of a tire manufacturer specifying how many lug nuts must be used on the wheel that the tire is mounted on. The tire has a max speed rating and max load rating, but shouldn't care how many lug nuts are used - just like a scope should have a max clamp force rating, but shouldn't really care how much torque is used. I assume it's really a guestimate based on the most common screw diameter, and of course the reason they do it is because nobody is going to trust shooters to calculate clamp force, but none of those facts make the torque value requirement more valid unfortunately.

 

[SharpsNitro]

I went through this with Ted at ARC with one of his unimounts and my Premier on a DTA. The scope would slip under recoil, especially with the 338 barrel. His solution was to have the turret sphere (that’s what I call it anyway) butt up against the forward ring (becoming a recoil stop). It worked fine.

I’ve carried this through to my TT525 in a DTA mount. It’s a very logical way to mount a scope. Why rely on ring friction, and possibly affect/damage the scope, by trying to keep it from slipping via ring friction?

 

[patriot07]

I went through this with Ted at ARC with one of his unimounts and my Premier on a DTA. The scope would slip under recoil, especially with the 338 barrel. His solution was to have the turret sphere (that’s what I call it anyway) butt up against the forward ring (becoming a recoil stop). It worked fine.

I’ve carried this through to my TT525 in a DTA mount. It’s a very logical way to mount a scope. Why rely on ring friction, and possibly affect/damage the scope, by trying to keep it from slipping via ring friction?

2 reasons I assume (although I am no expert):

1 - the scope wasn't designed to take recoil loads in that manner
2 - by definition, you're not clamping down on the scope enough to hold it in place via ring force, so it would seem very possible to have a wandering zero

 

[SharpsNitro]

I went through this with Ted at ARC with one of his unimounts and my Premier on a DTA. The scope would slip under recoil, especially with the 338 barrel. His solution was to have the turret sphere (that’s what I call it anyway) butt up against the forward ring (becoming a recoil stop). It worked fine.

I’ve carried this through to my TT525 in a DTA mount. It’s a very logical way to mount a scope. Why rely on ring friction, and possibly affect/damage the scope, by trying to keep it from slipping via ring friction?

2 reasons I assume (although I am no expert):

1 - the scope wasn't designed to take recoil loads in that manner
2 - by definition, you're not clamping down on the scope enough to hold it in place via ring force, so it would seem very possible to have a wandering zero

1. Very possibly.

2. No. I’ve used this configuration for four up years across multiple rifles. Why would limiting the forward movement of the scope under recoil by other than ring friction cause wandering zero? The whole point of this method is the scope is acting as a recoil shoulder against the ring. If anything it is a better mounting method. After all, this is what the rail mount euro scopes (Zeiss) do.

 

[koshkin]

Ilya, good to hear from you.

I will never argue with you, I like and respect you very much. I wish we could meet again and have a couple (or more) shots to celebrate the world of rifle scopes...

When I say "flexible ring", I mean, of course, the metal ring which can deflect enough to closely match the actual scope tube O.D., and not a scope ring that behaves like it's made out of rubber...

I travel for work a fair bit. I do not remember exactly where you are located, but perhaps if I end up in your area some time, it will be great to meet. One of the few pleasant side effects of work travel is that I can occasionally meet with people I normally only see once a year at SHOT.

I know what you mean by a metal ring that deflects and as far as arguing with me goes... why not? I do not see any problems with a polite and respectful argument, agree or disagree.

My basic concern with mounts where the ring half (or halves) is designed to flex is that the pressure applied to the scope tube is, by definition, asymmetrical. While deformation of the ring half, in principle, does not bother me in the slightest, I do not know how to determine if the ring is deforming or the scope tube is. I do not want to deform the scope tube, since there is stuff inside that I do not want disturbed. Given enough dedication and asymmetric pressure, ANY scope tube can be deformed. Different scopes would require different pressure and we really do not know which scope can tolerate what amount of pressure and in which exact spot. Given that, I do not know how we can reliably design a ring half that is supposed to flex without the risk making a round tube into an oval tube.

Now, if we have a perfectly round and stiff ring construction and the tube is not to spec, you will make what started out as an oval, into a round cross-section, which may not be good. However, I think our best chance of having a consistent mounting solution is to assume that the scope tube is round as are the rings, in which case very stiff ring halves will provide the most consistent engagement across the whole circumference of the scope tube.

Now, in all fairness, mechanical things are your field, more so than mine, so perhaps I am wildly off base.

ILya

 

[Quarter Horse]

If TT is indicating a max of 15 in.lbs. they know they have a problem. Vortex has a similar recommendation on the 6.5-20 Viper. Between myself and two other guys we have about six of them on various small caliber rifles. One scope was not dialing elevation accurately. The scope was sent in and returned by Vortex with a note that the scope was dialing properly but to limit the torque on ring caps to fifteen in.lbs. The guy with problem bought an in.lb. torque wrench and had no further problems. Vortex knew they had a problem.

A few years ago I PM'd Kortik regarding wet and dry torque. His response was that wet torque should be about seventy percent of dry torque. I have used this guideline successfully and and have the always wondered whether manufacturers of rings and or scopes are providing wet torque or dry torque?

Years ago there was no recommendation from scope or ring manufacturers that I knew of that provided torque limits. It was essential.ly firmly hand tight. Whatever the hell that meant. I was cautioned by a friend, who had been cautioned by a 'smith years ago, to tighten ring cap screws twice before the final time. The idea was that the first two times would even out any imperfections in the cap screw threads due to the repeated pressure and that they should be seated by the third time. It made sense to me so I do it.

Some things seem intuitive to me.
1. The wider the rings the more surface area should be in contact with the scope tube therefore a greater resistance to movement.
2. Lesser polish on the scope tube and the rings the greater abrasiveness and the resistance to movement.
3. If your picatinny rail is not absolutely level you will of necessity bend your scope tube when you mount it.
4. The use of rosin is standard in mounting a scope in Europe. Spuhr dictates it's use. If you have ever been in contact with the stuff you know why gymnasts, pitchers, etc. use it. It should be part of mounting any scope. Friction is the enemy of a scope moving.

If any of the above are not true in your experience, feel free to take exception. The reason I spend time here is many members know a hell of a lot more than I do.

A few years ago I boutght a TRG in .338LM. I mounted a SWFA 5-20x50 with Burris Extreme rings. The rail is a factory O moa. The scope eventually moved. I used Blue LocTite and everything has been OK since. I put up a post asking if anyone had used Burris Sigs. on a .338LM as the inserts would allow me to build in elevation. Everyone that responded said that the Sigs had done the job for them with no movement. I just bought a S&B PMII 5-25x56 during Euro-Optics sale and a set of the new Burris XTR Signature rings. I'll let everyone know how it works out.

 

[918v]

Push the scope forward in the rings until the turret housing stops against the front ring. Use minimum torque. I shoot 230’s at 2900 without a brake and am very familiar with big scopes in Spuhr mounts. That’s the best way to do it. You can use rosin but that’s messy.

 

[Burdy]

I just mounted a TT 5-25P on my Desert Tech in an ERA-TAC adjustable moa unimount. I torqued the screws to 25 in/lb. like I did on all my others and had the same thing happen. The parallax adjustment locked up solid. I backed it off to 20 and it freed up some, but was still catchy in a couple spots. I then backed them down to 15 in/lb and it freed up totally with no binding at all. Not comfortable with 15 in/lb, I tore it all down and mounted the scope in a tried and true ARC unimount and torqued it to 55 in/lb and tried the dial again. It was still completely free with no sticky spots! I guess it will live it's life in the ARC mount from now on.

Just bought my first ARC mount and I was nervous wreck going to 55 in lb on those ring caps...but it looks like everything is fine. This was on a LRHS.

 

[308pirate]

It’s about surface area. A well designed ring design will have maximum surface area touching the scope tube. With more surface area in touch, the less overall in/lb required as tension.

As far as I understand it, there is a second factor. Depending the the size of the bolt and threads, it could potentially require a different in/lb at the bolts. Meaning that 55in/lb could mean the same pressure on the tube as 30in/lb depending on bolt size and thread pitch.

I’m sure an engineer will come around and confirm or correct me.

Finally, someone who is close to understanding how torque, tension, and clamping friction are related.

This is a complex issue and most of what I read about in gun forums discussing how torque at a fastener creates clamp force has been fundamentally wrong. Reminds me of nitriding, with some many believing that it is some sort of surface coating.

It's also not black magic. There are plenty of time tested equations that predict this behavior.

I don't have the time to write a tutorial right now but I will leave some thoughts to dispel some of the erroneous information I see over and over:

1. Fastener tension is measured in units of force, not units of torque.
2. Fastener tension is not numerically equal to the force used to generate torque.
3. The same torque applied to two dissimilar fasteners will yield different fastener tension
4. The same torque applied to two identical fasteners will yield different fastener tension if the joints are not identical
5. The same torque applied to two identical fasteners, in two identical joints, will yield different fastener tension if one fastener is lubricated and the other one is not. The lubricated fastener will generate more tension in this example.

 

[powerspc]

Finally, someone who is close to understanding how torque, tension, and clamping friction are related.

This is a complex issue and most of what I read about in gun forums discussing how torque at a fastener creates clamp force has been fundamentally wrong. Reminds me of nitriding, with some many believing that it is some sort of surface coating.

It's also not black magic. There are plenty of time tested equations that predict this behavior.

I don't have the time to write a tutorial right now but I will leave some thoughts to dispel some of the erroneous information I see over and over:

1. Fastener tension is measured in units of force, not units of torque.
2. Fastener tension is not numerically equal to the force used to generate torque.
3. The same torque applied to two dissimilar fasteners will yield different fastener tension
4. The same torque applied to two identical fasteners will yield different fastener tension if the joints are not identical
5. The same torque applied to two identical fasteners, in two identical joints, will yield different fastener tension if one fastener is lubricated and the other one is not. The lubricated fastener will generate more tension in this example.

So, stipulate for a moment your bona fides in this area and it sounds as though you have some Mechanical Engineering background or at least an interest in it. Back to the question (or at least my question);

Scope maker XYZ specifies a maximum torque value of 15 in-lbs.

Scope Mount maker ABC specifies a torque range of 20-25 in-lbs.

What would you torque to?

 

[308pirate]

So, stipulate for a moment your bona fides in this area and it sounds as though you have some Mechanical Engineering background or at least an interest in it.

I don't feel the need to justify my bona fides in this area. If you think that anything I said is in error, please correct it.

Scope maker XYZ specifies a maximum torque value of 15 in-lbs.

Scope Mount maker ABC specifies a torque range of 20-25 in-lbs.

What would you torque to?

I would defer to the ring maker's recommendation.

While the scope makers know what level of clamping force will harm their product, they have no way of knowing what kind of ring design will be used to hold their scope. Because they don't know what ring design will be used, there is no way they can calculate what torque each individual ring screw has to be tightened to before the max clamping force is exceeded.

And while it's true that ring makers don't know what level of clamping force will harm every single scope out there, many ring makers also make scopes. So the way I figure, they have a better chance of being right.

You know what.......Against my better judgement I waded into this to try to provide some clarity and I regret doing so. You guys go back to discussing how this works using your own theories.

 

[powerspc]

For what it's worth I did reach out to TT today to see how they would respond, you can see their answer below.

Q.: Your manual recommends a torque value of the ring cap screws to a maximum 15 in-lbs. My mount manufacturer (Cadex Defence) recommends a torque value of 20-25 in-lbs. Do you have a recommendation? Scope is a TT525P, rifle is a Cadex Defence Kraken in .338LM.

A.: Thanks for the question, and our recommendation is to stick to what our manual outlines (15in-lbs). The optic could easily handle the increased torque without risk of damage, but is best to stick to the manual's recommendation.

 

[leftyk82]

Reading along......I just find that head-scratching when TT has no idea how many screws nor the size of those screws in any given set of rings or a mount. I wonder if they assuming that everyone uses Nightforce/Badger/etc rings with four screws?

 

[kortik]

For what it's worth I did reach out to TT today to see how they would respond, you can see their answer below.

Q.: Your manual recommends a torque value of the ring cap screws to a maximum 15 in-lbs. My mount manufacturer (Cadex Defence) recommends a torque value of 20-25 in-lbs. Do you have a recommendation? Scope is a TT525P, rifle is a Cadex Defence Kraken in .338LM.

A.: Thanks for the question, and our recommendation is to stick to what our manual outlines (15in-lbs). The optic could easily handle the increased torque without risk of damage, but is best to stick to the manual's recommendation.

Classic non-answer while paying some attention to the customer...

I hope somebody may be willing to create a simple calculation program to figure out relatively "accurate" torque settings. Certain factors to consider in order to arrive at value of realistic clamping force: estimated friction between scope tube and rings, estimated force to resist under recoil, which may be roughly 300+/-100 times the weight of the scope depending upon specifics of the rifle design and its caliber. May be include some other secondary factors as well. Then, knowing required clamping force, figure out the torque per screw depending upon ring design (number of screws, screw size, screw diameter and pitch, wet or dry friction in threads, etc.)

I would do it myself, just do not have time right now, business is now pretty hot and consumes a lot of my time.

 

[308pirate]

Classic non-answer while paying some attention to the customer...

I hope somebody may be willing to create a simple calculation program to figure out relatively "accurate" torque settings. Certain factors to consider in order to arrive at value of realistic clamping force: estimated friction between scope tube and rings, estimated force to resist under recoil, which may be roughly 300+/-100 times the weight of the scope depending upon specifics of the rifle design and its caliber. May be include some other secondary factors as well. Then, knowing required clamping force, figure out the torque per screw depending upon ring design (number of screws, screw size, screw diameter and pitch, wet or dry friction in threads, etc.)

I would do it myself, just do not have time right now, business is now pretty hot and consumes a lot of my time.

For that calculation to be anything more than mental masturbation one would need to model the joint behavior during the alignment phase of the rundown.

Remember than the majority of the applied torque is lost to friction between mating parts as they align and draw together, some more through underhead and thread friction, and then what little is left over goes to creating fastener tension.

ARC rings are the only ones I've seen where it would relatively easy to model. The typical set of rings, fuck that.....talk about a time dump. Like you, I know how to do it but I ain't doing it for free.

 

[308pirate]

Back to the real world

Torque the ring clamp screws to the ring maker's recommended torque.

If the scope moves, add rosin and move on.

 

[bjay]

My spuhr was torque 16-17"lb
And scope moved from 300nm recoil..tried 22" and so far so good..if your scope can only take 15"lb..that scope is rubbish

 

[308pirate]

25 lbf-in +/- 5 lbf-in and go. There are too many other more important things to worry about

 

[SLG]

This is one reason I by and large stick with NF scopes and NF rings. Easy button.

I find myself about to buy a spuhr becasue I basically have to for what I want to accomplish, but I'm dreading it.

 

[918v]

Why are you dreading it?