300 WSM Upper for 308 Lower Receiver?

[buckeyeoptics]

I really like the new NEMO 300 Win Mag AR, but not a big fan of the price tag.

Is anyone manufacturing a complete upper receiver in 300 WSM to fit a 308 lower receiver ??

[mic2377]

Armalite used to make one in 300 WSM. Apparently they no longer support them, and they took lots of proprietary parts.

I believe that you could probably find someone to make you one, but it would likely be a custom deal particularly if you are talking about a DPMS pattern.

Some of the big disadvantages would be the limited OAL you can feed from a standard 308 AR mag, and bolt thrust. This is limiting in regards to running long, high-BC bullets without eating up too much powder space into the cartridge. I have 7 WSM bolt gun and optimal cartridge length with a 162 A-max is MUCH longer than the factory stated max OAL. Also, the bolt head is considerably larger on a WSM = reduced bolt strength, so you would likely have to watch the pressure of your loads.

I still think it would be pretty neat, but I just don't think you would get quite all of the advantages you would imagine from the WSM cartridge.

[yellowfin]

There was also something done with the 300 SAUM which was essentially the same as a WSM but a little better suited for autoloading rifles. I'm very curious as to what direction could be taken now that .308 AR's keep getting more and more popular as time goes on instead of them being a novel afterthought in the market.

[dewatters]

The ArmaLite was chambered for the SAUM, not the WSM. I seem to remember SSK offering WSM conversions, but I don't think that they list them anymore.

[constructor]

Be careful with these things. No one makes an extractor that works with the magnum rim dia. Well, someone grinds them down to make them work and then they break. When the 308 extractor travels out far enough to snap over the rim the back of the extractor contacts the lugs of the barrel extension and stops forward movement of the carrier.

[yellowfin]

How much trouble would it be to fabricate one that is satisfactory? Is it simple enough to do that a gunsmith or a machine shop could make a few? Does Armalite still make spare parts so an extractor could be gotten as a sample? Also, so nobody currently makes one--how long will it take for a company to get tired of there not being someone doing it to take it upon themselves to do it?