American Rifle Co. introduction - M3 Scope Mount

[karagias]

Gentleman,

This message has been approved by Lowlight and is intended to serve as an introduction rather than an advertisement.

I would like to introduce myself, Theodore Karagias, and my company, American Rifle to the community.

American Rifle Company

I recently started manufacturing scope rings designed to comprehensively address the connection between rifle and glass. The benefits are:

1. Rings will not damage your scope. In fact, no other scope ring can provide as tight a grip without damaging the tube.

2. Crowned rail interface accommodates variations in rail profile and ensure return-to-zero performance.

3. Light weight and high strength. A 30mm diameter by 35mm high pair of rings weighs in at only 7 ounces. Ring set is constructed from 7075 T651 aluminum and 17-4 H900 stainless steel.

4. High precision. Rail and scope interfaces are machined during a single setup using a 5-axis CNC machining center.

I welcome all comments and questions, good and bad, so fire away.

And as for me, I am a mechanical engineer with 17 years of experience designing automation equipment for the aerospace industry and surgical devices for orthopedic trauma. I have been interested in firearms since I was born. Other interests include manufacturing technologies, the outdoors and a yellow lab named Oscar.

Best regards,

T

 

[Switchblade]

Re: American Rifle Co. introduction - M3 Scope Mount

Welcome! Nothing like new products to keep the field in check!

 

[jrhammons]

Re: American Rifle Co. introduction - M3 Scope Mount

T

I have a question looking at them. Since they are hinged do you have problems with the scope moving while the rings (the top ring, not base) are tightened? Tightening the one side would seem to rotate the scope as most current products I have used do and the scope would lose level and I can read that it says they won't but how is it not since you are pushing on one side of the scope as you are tightening.

Rob

Also when should we be receiving our free "sample rings" LOL welcome to the Hide and would love to see em.

 

[karagias]

Re: American Rifle Co. introduction - M3 Scope Mou

Excellent question. Short answer is no, the scope does not noticeably rotate when tightening the screws.

Long answer (optional): The lower portion of the ring is more effective than the upper portion at preventing the rotation of the scope while tightening the screws. Some relative motion must occur between the ring and the scope as the ring is stretched around the scope tube. However, since there is more friction between the ring base and the scope than there is between the ring cap of the scope, the scope does not to rotate with respect to the ring base when tightening the screws. Instead, the ring cap slides over the scope. This was predicted by the finite element analysis used to simulate the clamping action of the ring and its effect on the scope. I will try to provide an .avi showing the result of this analysis.
Rotation of the scope is a problem with other rings because as the screws are tightened, the corners of the ring cap (which is usually more flexible than the ring base) are forcefully driven into the scope, effectively gripping or pinching it. As the screws rotate the cap either clockwise or counterclockwise, the cap effectively takes the scope for the ride. The gripping corners of the cap are also responsible for marred finishes and small indentations.
My rings don’t have this problem since there is no offset between the screw axes and the scope tube, which eliminates bending moments in the ring cap. No bending moments equals no pinching of the scope tube enabling the ring cap can more easily slide of the tube during clamping.
The important thing to take away from this is that American Rifle’s ring does an excellent job of uniformly distributing the clamp loads over the tube. Small areas of intensified stress are not present. This allows one to apply more torque to the screws without the risk of damage than would otherwise be possible with any other ring. More torque yields a tighter grip. In fact, while most manufactures are strict about limiting screw torques to 15 inch-pounds, I will happily apply 30 inch-pounds to the screws of a ring clamp around my Schmidt & Bender 3-12x42.

T

 

[Switchblade]

Re: American Rifle Co. introduction - M3 Scope Mou

Those rings look pretty darn nice but I no longer have my first born to barder with(He's in Syracuse) but a Second Born Straight A is available for indentured servitude

 

[jrhammons]

Re: American Rifle Co. introduction - M3 Scope Mou

T thanks for the info. look forward to trying them out at some point. I am with Switch though. I have two boys that are great slave labor if you need them!

 

[shane45]

Re: American Rifle Co. introduction - M3 Scope Mou

Hello and welcome. Now on to being devils advocate

"In fact, no other scope ring can provide as tight a grip without damaging the tube."

I dont see how this fact could be true. Please elaborate. For the cap to be able to swing over the top of the tube, there has to be significant lead in and clearance. Enough, I would think that it would make for less of a contact patch on the tube its self compared to other manufaturers like Ops2Inc or Seekins that keep the gaps small and contact large or even no gap style like Barret and TPS. How can you get a tighter grip holding less of the tube(speculation on my part)?

 

[JB5812]

Re: American Rifle Co. introduction - M3 Scope Mou

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">without damaging the tube</div></div> Well... Technically he said No rings can get a tighter grip "without damaging the tube"... So maybe it's as tight as they can be, without causing ANY damage, marks, mars, or effect on the scope what-so-ever...

(Speculation on my part as well, assuming I am interpreting that right)

 

[karagias]

Re: American Rifle Co. introduction - M3 Scope Mou

Thank you for the question gentlemen.

In regards to the cap swinging over the tube, please take a close look at the top two diagrams of the "Eliminate Damaged Scopes" page of my web site. Click on each to enlarge. As the cap wraps around the tube, the potion of the cap extending beyond the 180 degree contact portion drafts away from the tube allowing it to clear. The drafted portion is actually a radius that is concentric with the hinge pin, rather than the tube. When the scope is place in the ring base, the cap can swing over the tube without touching it. A close look at the diagram depicting the tangential placement of the screw will reveal this.

Regarding contact area, American Rifle's 30mm ring is 28mm (1.102 inches) wide, 26mm (1.024 inches) of which contacts the scope. One millimeter is lost at each end due to a chamfer. Both the ring base and the cap contact the scope along 180 degrees of the circumference but not along the full 26mm width. There is some loss of contact associated with the overlapping design and the hinge. The measured contact area of the 30mm ring is 3.34 square inches. (3.80 square inches is the maximum possible for a 30mm ring with 26mm of engagement.)

For comparison, let us consider the 30mm 4 screw Seekins ring. Seekins is kind enough to provide us with a spec indicating the ring is 0.8 inches wide. Let's give him the benefit of the doubt and assume his contact with the scope is 100% efficient (no gaps) giving us 2.97 square inches.

Therefore, American Rifle's M3 ring has 12% more contact area than the 4 screw Seekins ring. Seekins also make a six screw ring that has 11% more contact than American Rifle's M3 ring but I'll address that soon.

So what does contact area have to do with gripping the tube? We rely on friction to hold the scope in place when clamped in the rings. Reference to a mechanical engineering handbook (pick one) will tell us that friction is largely independent of surface area. In fact, engineers approximate friction force as the product of normal (or contact) force and a coefficient of static friction. This is a reasonable approximation for contact between two steel surfaces or two anodized aluminum surfaces as the case may be between scope and ring. It is not a good approximation for a tire on a road surface as the mechanism by which adhesion occurs between rubber and asphalt is much different than that which occurs between two smooth anodized aluminum surfaces.

Since friction is largely independent of contact area, what we really care about is how much force we can deliver to the scope without damaging it. If the loads can be uniformly distributed, more contact area is a benefit in this regard because distributing the screw force over a larger area results in lower stress (pressure). But in truth, distributing the load uniformly is difficult to do and this is where American Rifle enjoys an advantage, even without the advantage of 12% greater contact area. The shape of the M3 ring cap and the placement of the screws ensures that no edges of the ring are forcefully driven into the tube. If the screws are offset from the tube, as they are in every other design that I am aware of, the corners of the ring near the screws which contact the scope will be driven into the scope tube as the ears or the ring are driven (or pinched) together by the screws. This results in an intensification of stress within the tube potentially resulting in damage. This is purely a function of the shape of the ring and the placement of the screws. In engineering, an offset force results in what's known as a "moment". Engineers generally try to avoid imparting moments whenever possible as they can be difficult to deal with.

Lastly, in regards to the Seekins 6 screw ring, increasing the available screw force by 50% while increasing the area by only 12% will increase the screw force per unit area by 34%, assuming that the force can be uniformly distributed. The actual increase in stress will be much higher, again, because the offset screws intensify the stress near the gap between the upper and lower portions of the ring and because uniformly distributing the force imparted by an offset screw is difficult, if not impossible.

I hope this helps, and again, thank you for an interesting question.

T

 

[shane45]

Re: American Rifle Co. introduction - M3 Scope Mou

Thank you for the reply. Ill spend a little while digesting what you stated. Interesting and informative. Thank you!

Shane

 

[motochamp250]

Re: American Rifle Co. introduction - M3 Scope Mou

very interesting product. looks like a different and well thought out design... welcome to the hide and good luck!

 

[karagias]

Re: American Rifle Co. introduction - M3 Scope Mou

Thank you.

 

[spr1]

Re: American Rifle Co. introduction - M3 Scope Mou

Very nice design! Hopefully volume will help you reduce price.

 

[karagias]

Re: American Rifle Co. introduction - M3 Scope Mou

Funny you should bring that up. Price has just been reduced to $199.99.

 

[shane45]

Re: American Rifle Co. introduction - M3 Scope Mou

I though about your explanation long and hard and reviewed the pictures on your websight. I think that I should clarify what I consider tube damage. I consider tube damage clamping it hard enought to take it out of round. Ring marks is irrelevant superficial damage. I dont care about resale, I care about operational integrity. The rings are far thicker than the walls of the scope tube. The tube is whats going to give given the chance. Keeping with the example of Seekins rings, the only place for the tube to come out of round is the very small gap. So basically it aint happening. Now to your design, you actually pull in a direction away from the tube and if I interpret correctly make this an area of no contact. You have now created an area possibly big enough for the tube to deform into.

 

[karagias]

Re: American Rifle Co. introduction - M3 Scope Mou

Shane,

I am glad you brought this up. I consider damage to be a marred finish, an indentation, and a problematic departure from circularity. In regards to a marred finish and indentations, both are the result of high stress which necessarily must deform the tube. Hook's Law for elastic materials tells us that:

strain (deformation) = stress / Young's Modulus

Young's Modulus for aluminum is approximately 10 million psi.

This basically tells us that the tube (and the ring) will deform when stressed. What's more, the loads applied by the screws are large and result in high stress, so deformation will be significant in both my rings and any split ring with a gap on one or both sides.

So what becomes important is the resulting shape of the tube when clamped within the ring. The best way to see this is through the use of finite element analysis. This can be rather involved and difficult to present within this forum. But, if you ever find yourself in the Seattle area, track me down and we can get deep into this.

For now, I can offer this analogy. Imagine a rubber tube with a perfectly circular cross section. Wrap a cord around the tube once so that the ends of the cord are going off in exactly opposite directions. Assuming there is no friction between the imaginary cord and tube, pulling the ends of the cord will deform the rubber tube. However, the deformation will be such that the section of the tube remains circular along its length but with a reduced diameter near the cord. This is approximately how American Rifle's ring works. It contacts the tube along its entire circumference. Where the two parts of the ring overlap, the screws effectively pull on the cord. The ring cap is designed to be compliant in order to conform to the tube. The ring base is less compliant than the cap due to its lower structure which is necessary for the rail interface. However, a serious effort has been made to "soften" it as much as possible by hollowing it out keeping only the material necessary for strength and function.

I don't have a good analogy for a conventional ring with offset-screws but finite element analysis indicates that the ring is squeezed on either side at the joints between the upper and lower portions of the ring. The resulting tube shape is something like and egg with its sides pushed in.

If someone can tell me how to attach images to this thread, I will be happy to do so. I'd like to share two FEA displacement plots that will illustrate the difference between the two designs.

T

 

[shane45]

Re: American Rifle Co. introduction - M3 Scope Mou

More for me to chew on. Email me the pics and I will post them up for you. I particulerly appreciate these kinds of threads because I always feel I have learned something from them.

Thanks!
Shane