Rifle Scopes SCOPE TUBE MATERIAL

[SAKOstalker]

I notice most scopes use 6061-T6 while some promote 7075 T-6...

Leupold used this 6061_T6

I heard Schmidt & bender uses 7075 T-6

i got this from another forum :<span style="font-style: italic"><span style="font-weight: bold">"The strength is double! 40-45K on the 6061 T6 vs. 80-85K for 7075 T6. Most every property of 7075 T6 is favorable by a large margin over 6061.

7075 matches many properties of stainless steel/CM etc..."</span></span> also : <span style="font-style: italic">you could makes the wall thickness's thinner etc... to decrease weight but the biggest thing to me is the portion of the tube that the rings go on. 7075 T6 has a memory that's out of this world and very hard to dent, bend etc... Your almost getting the properties of TI at the price of Aluminum.</span>


anyone have an opinion on whether this matters?

 

[PCR]

Re: SCOPE TUBE MATERIAL

I've wondered the same thing

 

[SAKOstalker]

Re: SCOPE TUBE MATERIAL

I have confirmed S&B uses 7075, which is a stronger alloy. Wonder what other makers use.....

 

[Rob01]

Re: SCOPE TUBE MATERIAL

According to their site Nightforce uses 6061 T6 also so not sure how much the material has to do with the scope toughness but all things being equal I would rather have a stronger material.

That said, if it gets to the point the scope fails due to the material it is made from I think you have bigger problems on your hands

 

[M40_A1]

Re: SCOPE TUBE MATERIAL

Take a magnet and place it on the side of your scope tube. If it falls off the scope is defective and should be replaced.

 

[Supersubes]

Re: SCOPE TUBE MATERIAL

what?

 

[Supersubes]

Re: SCOPE TUBE MATERIAL

I think there was a time when uso was using a little of both but it was causing variations in the way the anodizing came out. I guess they don't act the same at all(6061 vs. 7075).

 

[USMCj]

Re: SCOPE TUBE MATERIAL

Is USO using 7075 now?

 

[JBW3]

Re: SCOPE TUBE MATERIAL

6061-T6 on the USO scopes, 7075-T6 is a little brittle.
John III

 

[High Binder]

Re: SCOPE TUBE MATERIAL

Guys, harder isn't always better (haha) anyway the harder the material the more subject it is to cracking as it's more brittle. So just because a scope body is made out of one material or another doesn't means one is better than the other. For any fellow Mech-engineer out there can show you on a stress diagram that the 6061 is only marginally (subjective term) more flexible than 7075 and as such I don't think it makes much difference what material the body is made of...

 

[AUJohn]

Re: SCOPE TUBE MATERIAL

Does not matter. By the time you have an issue things like lense about mounts are already gone.

 

[salmonaxe]

Re: SCOPE TUBE MATERIAL

Whatever anodizing that USO uses, completely owns NF. I had the knurling on a scope turret cover on a USO scratch the hell out of a NF turret.

I'd say that one would want flexibility in a scope body material so it doesn't crack over time due to vibration and stress risers. It's the surface treatment that will keep scratches and abrasions down.

I really wish NF would change their surface treatment. It's not very tough.

 

[Dangeruss970]

I don't know. I'm fairly convinced that the non-use of 7075 t6 aluminum in scope bodies is almost purely a cost-saving measure. It's way more expensive than 6061-t6. Everyone knows this. The surprising part to me is that I continue to see high end scope makers continue to use the lesser grade. When you pay $2000-$3000+ for a scope, you should rightly assume that it's made with nothing but the best. 7075 is too brittle? I don't really buy that. If that was the case, wouldn't there be a bunch of cracked mil-spec receivers out there? Also, 7075 is way more corrosion-resistant than 6061. If 7075 is too brittle, why are plenty of scope mounts made of them?

 

[TorF]

Take a magnet and place it on the side of your scope tube. If it falls off the scope is defective and should be replaced.

+1

 

[The_FNG]

A lot of epic bumping going on lately..

 

[918v]

What about Zriss?

7075?

 

[scatsob]

I know this is a really old thread, but on a rifle scope it doesn't matter which alloy is used. There is no load applied to a scope that will make one material a better choice over another. Machining maybe but aluminum is soft. Scopes made of one are not "better" than ones made with the other.

 

[918v]

What about if the scope is banged against something hard? Would not the additional toughness of 7075 be better in retaining the original dimensions? 6061 would dent and screw up the alignment of the lenses, etc.

 

[Pinecone]

7075:

It is strong, with a strength comparable to many steels, and has good fatigue strength and average machinability, but has less resistance to corrosion than many other Al alloys.

T6 temper 7075 has an ultimate tensile strength of 74,000–78,000 psi (510–572 MPa) and yield strength of at least 63,000–69,000 psi (434–503 MPa). It has a failure elongation of 5–11%.

7000 series alloys such as 7075 are often used in transport applications, including marine, automotive and aviation, due to their high strength-to-density ratio.

6061:

It has good mechanical properties and exhibits good weldability.

T6 temper 6061 has an ultimate tensile strength of at least 42,000 psi (300 MPa) and yield strength of at least 35,000 psi (241 MPa). More typical values are 45,000 psi (310 MPa) and 40,000 psi (275 MPa), respectively.

2024 alloy is somewhat stronger, but 6061 is more easily worked and remains resistant to corrosion even when the surface is abraded

All material choices are a compromise. You get some more desirable properties and some less desirable.

 

[Rob01]

if it gets to the point the scope fails due to the material it is made from I think you have bigger problems on your hands

I will stick with what I said almost 4 years ago.

 

[scatsob]

^^^Word

I will stick with what I said almost 4 years ago.

 

[918v]

It may be that either material is serviceable, but which one is better?

And now that titanium composites are readily available, would that not be better still?

I recently ordered some AR billet receivers and had to pay 50% more for 7075. Apparently they are more difficult to machine, but pretty much indestructible.

So if your rifle falls out of your truck as it's rolling down a hillside, what scope tube material do you wish they had used?

 

[scatsob]

Neither is "better" for this application and would just be guesses at best. During design the tube will be sized for whatever loads it will experience based on the material properties. So if it is designed to take a certain shock load and that translates into a tube thickness calculation than they will have different tube thicknesses but one won't be better than the other. Rolling down a hill won't bring out any differences in scope material, just ruggedness in design or lack there of.

 

[918v]

But the tube thickness is limited by the ring size and internal elevation travel. The tube thickness can only vary so much. So if the tube thickness is limited to .1" and 7075 is stronger, then it is better.

 

[scatsob]

One would have to define "stronger" in relation to the trauma you are talking about. 7075 is harder and more brittle, so in a situation where your scope might impact something hard it will transfer more energy to the internals and glass and would run a better chance of damaging them over the "softer" 6061. 7075 is "stronger" in yield and ultimate tensile strength but neither of those will come into play unless you place your scope between two boards and run it over with a large truck . Still, at the end of the day it really does not matter. I am sure you could spec a scope made out of chrome moly steel and it would be relatively indestructible but heavy as hell and not that much more indestructible compared to one made out of aluminum to justify the weight increase.

But the tube thickness is limited by the ring size and internal elevation travel. The tube thickness can only vary so much. So if the tube thickness is limited to .1" and 7075 is stronger, then it is better.

 

[Trespasser]

Both alloys with a T6 temper have close to the same elongation at break. (12% for 6061 versus 11% 7075.) This difference in brittleness is negligible when 7075 is significantly stronger, harder, and tougher. The big drawback is cost. If people associate 7075 with brittleness, this may be from experience with forged AR components.

 

[scatsob]

I guess we will all have to agree to disagree . Rob is right on, it does not matter at all what your scopes are made of when it comes to the two alloys of aluminum being discussed, you are worrying about nothing.

 

[scharfschutze762]

A lot of popular scopes are not machined but extruded or "hydroformed" tubes so the material i would think has to be fairly malleable.

 

[drum13]

What about using steel for the scope tube? Didn't the Unertl 10x have a steel tube or is that just urban myth?

Going to venture a guess that the OP was looking for the most rugged scope available which is a topic I've been thinking about as well.

 

[918v]

Machinability is an issue. You have to be able to hold aerospace tolerances on thin steel that warps if you cut on it too fast. That's why aluminum is better.

 

[M40_A1]

What about using steel for the scope tube? Didn't the Unertl 10x have a steel tube or is that just urban myth?

That's what I was refering to when I suggested the magnet test;-) Not a myth at all. Even the older Unertls, Lymans, Redfields and Weavers were steel, as well as many European tactical scopes even today. Until lightweight aluminum hunting scopes came into vogue, steel was it (except for maybe brass in the Civil War and such).

 

[TallShot]

A lot of epic bumping going on lately..

You noticed too?

Saw one the other day that was 6, yes SIX, years old.