steel vs aluminum rings

Merllin said:
I just like steel rings because of the weight... I dunno, Id rather have a heavier gun then a lighter one... Backwards thinking I know, but I hold the rifle more steady with the extra weight.. (Rings are only a part of that obviously)...
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Yes once you add in the human factor you may as well just go home. :runaway:
 
cosmic said:
HP - I would think modulus of elasticity (E) is a more important property, rather than yield strength. If memory serves, aluminum is about half that of steel. If so, it would deflect twice as much as steel under the same (scope-induced) shaking forces...
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Cosmic, you're right about the modulus of elasticity being much lower for 7075 than the higher grades of tool&die steel (4050 & the like). However, low modulus of elasticity = deflection ONLY for constant static forces (i.e. when there are high clamping force), which isn't valid for the ring & rail bodies since the contact areas are maximized by design. In face, a low modulus of elasticity allows the aluminum rings to better absorb impact without permenant deformation (or yield, as the experts call it). So a reasonably high, yet lower MoE is better for the ring bodies.

Grizzlypeg said:
Also wondering why, if aluminum beats steel in all those aspect, don't they make the fasteners for the rings and bases from aluminum too?
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The answer above sums it up. The fasteners are under huge tensile and shear stresses, and the low MoE of 7075 is not good under clamping forces. i.e. the threads wouldn't last as long as those of steel torqued.

Grizzlypeg said:
How come they don't save up a pile of weight and make the bolts and receivers from aluminum as well?
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Again, you're not looking at the whole picture. Thermal properties are very important for receivers and actions, and although the high thermal conductivity of aluminum would benefit heat dissipation, conversely it would also cause the receiver to deform more easily when overheated. Simply firing 10 magnum rounds in short intervals would be enough to permenantly deform the aluminum around the chamber. Such a limitations doesn't exist for rings & bases. And BTW, if you read my excerpt above, the M16's receiver has aluminum parts, and I would assume if it's good enough for the U.S. Army's main battle rifle, it should be good enough for other extreme uses as well. :kickInTheNuts:

Grizzlypeg said:
Even where money is no consideration, such as auto racing, they use steel studs and axles, steel head bolts, crankshafts, and never use aluminum connecting rods except for drag racing motors that are only expected to hold together for a short time period.
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I agree with you, steel just "sounds" more robust than aluminum, but then again you have to look at facts: a lot of industrial applications have switched from steel to aluminum: doors & windows, car bodies, etc. Alaso, you're neglecting the thermal factor. Aluminum brake discs don't work very well :cool: But almost all F1 engines have aluminum blocs and cylinders nowadays, so even that's not necessarily a limitations whent he right aluminum alloy is used!!!
 
HyeProfile...

How do rings/bases made from solid 400 series stainless steel that is hardened and stress relieved before it is machined and finished in a nitrided matte black oxide finish, compare to rings/bases made from solid billet 7075-T651 Aluminum that are type III hard anodized? :runaway:
 
Cosmic, you're right about the modulus of elasticity being much lower for 7075 than the higher grades of tool&die steel (4050 & the like). However, low modulus of elasticity = deflection ONLY for constant static forces (i.e. when there are high clamping force), which isn't valid for the ring & rail bodies since the contact areas are maximized by design. In face, a low modulus of elasticity allows the aluminum rings to better absorb impact without permenant deformation (or yield, as the experts call it). So a reasonably high, yet lower MoE is better for the ring bodies.


Hmmm - Debatable... Under the impulse of firing, a bending moment is created by the scope inertia. The rigidity of the rings and bases determines the amount of beam bending imposed back upon the scope. I would think that a high modulus of elasticity would be a good thing...
There was a post on here not too long ago showing a failed aluminum one piece base on the 300 Win Mag. The base had let go at the rear screws and twisted upward like a pretzel. I dont think one has to do a detailed FMEA to establish that steel would have been a better choice.
 
cosmic said:
Hmmm - Debatable... Under the impulse of firing, a bending moment is created by the scope inertia. The rigidity of the rings and bases determines the amount of beam bending imposed back upon the scope. I would think that a high modulus of elasticity would be a good thing...
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I agree that the lower MoE of Al implies that slightly more bending moment is transfered to the scope, but that is partially offset by the fact that the amplitude of the forces/moments/vibrations transmitted to the scope is lower in Al than in rigid steels. Basically, the more rigid the material, the higher the "shock value"...

cosmic said:
There was a post on here not too long ago showing a failed aluminum one piece base on the 300 Win Mag. The base had let go at the rear screws and twisted upward like a pretzel. I dont think one has to do a detailed FMEA to establish that steel would have been a better choice.
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I gather from your description it sheared around the rear screw, or did the threads let go? I also doubt it was made out of 7075. More probably it was cheaper 6061.

I personally use TPS TSR W Series tactical scope rings that are manufactured from a solid billet of 7075-T651 aluminum. They are also available in 1215 alloy steel or 416 Stainless Steel, but note that the 7075-T651 version has the same or higher tensile/yield/shear strengths than the 1215 alloy. The cross-bolt and tightening nut are from alloy steel for the aluminum and steel rings, finished with black oxide to Mil-C-13924 standards, wheras they're in 304 stainless for the stainless models. The ring body and capare finished in a matte black hard anodize to Type III per Mil-A-8625 standards in the aluminum rings. In the steel rings, they are finished with black oxide to Mil-C-13924 standards. The stainless steel rings are bead blasted to a matte finish. The ring caps are securely fastened to the ring base with (4) four Torx®screws. HRT and W rings utilize a smaller cross-bolt to fit all brands of bases.

Cosmic, seems you're a knowledgable person in material properties and material selection/applications, but I have high confidence that the 7075s I have on won't fail due to the tested yield/shear numbers which are as good as steel, so despite the fact that there is healthy debate about which one is better, I stand by my original statement that the 7075 versions are just as good as steel, if not better...

However, here's a twist. Some people believe that a combination of both materials might be better for mounting scope: A fellow shooter has a 1215 alloy steel base and 7075-T6 rings, and he swears by that setup. If you think about it, the steel base is very stiff and minimized the bending moment that gets transfered to the scope, and the 7075 rings are good to dampen the vibrations and won't mark the scope or induce as much force and shock onto the scope... Anyone else use that kind of setup?
 
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