AR 15s in calibers other than 5.56 NATO

[someguy2800]

The picture of the 30AR looks awful similar to 6BR. Why does no one offer a 6BR upper? Shoulder too sharp to feed worth a flip? If that was able to be offered, game over for the other 6mm offerings.

Since the 450bm fits, wonder how a rimless 41 cal 1.75” case would do? Even a rimless 414 supermag would be fun. Yes, I’ve heard of the 400 legend, but I’m a 41 fan for it‘s relative oddness.

It cracks me up the AR platforms have turned into the semi auto TC Contender and Encore. I love it.

Two problems. First the overall length of 6mm br is about .150” too long for an AR15 magazine. 2nd problem is bolt thrust. A standard AR15 bolt will not support 62,000 psi with a .473” case head. It is fine with the 5.56’s .378” case head, but as you go up in case diameter, you have to go down in pressure. That is why a 6.8 spc is a slightly lower max pressure of 58,700. 450 bushmaster is only 38,700, and the big 50 Beowulf is only 33,000.

The way around this is to make an oversize bolt and barrel extension with an improved design to handle more both thrust. Below on the left is my 358 yeti bolt from MDWS. This allows you to run 62,000 psi with a .473” case head in a standard AR upper. You could build a 6mm BR upper with this, but you would have to load it short to 2.3” for it to fit in a magazine.

MDWS did make a similar wildcat for a bit called 6mm Lynx.

6mm Lynx home

This is the home of the 6mm lynx it is a stretched 6 brx for the ar15 based on the 6.5x47 case. The Lynx is the same case length as the 270 AR and 257 Bobcat. it also shares the same shoulder position but the case is blown out to brx width. quick load predicts 44.5 gn case capacity compared to...

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