Re: DPMS 300 SAUM Whats it worth?
You have what is called a non-fungible item. Meaning that since even Remington has abandoned the SAUM concept, the demand for the rifle isn't what it would be if it was in a more commercially acceptable chambering, such as the 260. Now, don't get me wrong, I think the 300 SAUM is an excellent cartridge, and there are plenty of individuals who load their own ammunition that might make use of it. However, those same people may choose a round that may suite their specific needs a bit better.
So, they don't make it anymore, and they don't because the round/rifle combination just wasn't popular enough, given their somewhat limited production base.
I don't think it would qualify as a collector's item.
Actual value would be about the same as any other DPMS LR rifle. You'll just have a bit more difficulty moving it, due to reduced demand.
That said, it would be a great hunting/target rifle, and if you reload, I would suggest you follow Redmanss advice and go shoot the crap out of it.