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Miroslav

Dimensions barrel ext./ bolt new .308 ar designs

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Hello,

 

I'm very curious about the dimensions of the new .308 ar-style rifles that have been released over the last years. As I'm in a country where these are not available, I haven't been able to feel one up with my calipers.

 

I've compared the geometries of my m1a, common bolt action rifles (chambered for cartridges w .308 sized case head and pressure) and the original ar-10 bolts. The lug shear area is about the same on all of those rifles. I'm very curious on how the designers of the new generation of. 308 ar rifles shrunk the diameter of the barrel extension and bolt carrier.

 

The main dimension is of course the outer diameter (s) of the barrel extension. I'm also curious about the outer diameter of the bolt lugs, the diameter of the bolt head between lugs, the width of the lugs along the direction of the barrel and perpendicular to the barrel. If it would be convenient for someone to do these measurement, I'd appreciate it.

 

If anyone knows where I could find a full set of cad drawings, that would be a big win, of course.

 

Cheers

 

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Google (an arfcom thread) told me that dpms were able to do it by selecting a very special alloy, and that the scar mk17 is somewhere in between the ar-10 and the "gen 2" rifles.

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So I  googled some more (travel day and I'm not driving) and found that several of these bolts, at least both the POF revolution and the scar mk17, are made of Carpenter aermet steel alloy (possibly aermet 100). Aermet 100 seem to have more than 50% higher strength than carpenter 158, which I believe is the most common steel for these components. I think this difference more than compensates for the smaller bolts.

 

I might do a simplistic stress analysis when I get back home.

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