Since seeing that RDB-S, something has been tickling the back of my brain and I finally figured out what it is.

Would it be possible to;
1. Put an RFB barrel in the RDB-S
2. Cut barrel down to 16", thread it, then...
3. Shoot .300blk?

Or is this something only for ARs?

My first, uninformed, question would be: Can you safely shoot .300 in a .308? And would you have to have the chamber redone for .300?

May be 'easier' to get a custom .300BO bbl done for the RDB rather than cobbling together something else?

I dunno. My thinking was "Are the .30 barrels in ARs chambered for .300blk?" I thought that was part of the beauty of .300....you just needed a new barrel for the rifle.

.300 Blackout and .308 Remington are completely different cartridges. One doesn't just drop an AR10 barrel into an AR15 platform. KelTec's systems can't be much different.

Ask KelTec for the possibility of a 300blk barrel. They're only a phone call away.

See, this is why I ask stupid questions. The obvious sometimes eludes me.

FWIW, the company keeps saying there'll be other chamberings soon, and the .300 is sort of next in line in the natural progression from .223/5.56. Depending on how big of a hurry you're in, the question at some point in the foreseeable future may be whether you can get an RDB barrel to swap into an S - or whether Kel-Tec will simply make an RDB-S in .300.

You could always call them and ask what are the chances of them producing one in .300BLK. Couldn't hurt anything at the very least, and if they get enough calls asking the same question, maybe they'll just decide to make one.

.300 Blackout does not need a .308 barrel. It will fit in an AR-15.... You'd know this if you'd looked even casually at the round.

Look at the case pressures...

Frankly, the likelihood of KelTec offering other calibers is higher than many other makers, just be patient.

Yep, as handy as that thing looks, I've kinda got my fingers crossed hoping it catches on and does well. I can totally understand folks drooling over the idea of that rifle in that caliber, especially for hunting. As a survival rifle, it made it all the sense in the world to introduce it in 5.56/.223 feeding from AR mags as much as it makes all the sense in the world that they would follow it up in a variant in a larger caliber tossing a heavier projectile, ideally feeding from AR mags.

Bullpups have long been controversial. Anyone who shoots one will want one, but I doubt it will ever be "widely popular." Keltec is small enough that they don't need huge interest to break out different calibers.. time will tell.

I agree on all points. I want bullpup everything now. And yes, you’re far more likely to see Kel Tec offer their bullpup in .300 BLK than you are to see Steyr, FN or IMI offer one in another chambering.