Okay, I'm admittedly still something of an AR-n00b. My brother and I bought a pair of lower receivers from Palmetto State some time ago, and are finally getting around to building them up.

Tonight's football-and-beverages discussion brought the question, "can these be built for use with a .300 Blackout upper?"

My brother asked, "How do we find that out?"

My instant answer was, "Let's ask SigForum." So here I am.

Thanks, all!

Yes.

.300 Blackout uses a standard AR15 lower receiver.

The “multi” more than likely refers to .223/5.56/300blk.
I have a couple of 5.56 ARs and a couple in 300blk.
No difference in the lowers on any of them other than cosmetic stuff. Function is the same.

Ha! I told my brother, "we'll have an answer in less than ten minutes." And I was right! SF rocks!

Thank you, fellas. Now we've got more planning and shopping to do....

MULTI simply means it can be used for multiple calibers,

and there are lots and lots of choices

quote:

Originally posted by lyman:
MULTI simply means it can be used for multiple calibers,

and there are lots and lots of choices

Exactly! Another new caliber released this week: Federal .224 Valkyrie.

I have an Andersen lower marked Multi cal with a 7.62x39 upper

I'll drift my own thread here and ask: If we were looking for piston-driven uppers in .300 BLK, what would SF recommend?

And because I'm still newbie, can I tell by looking at an upper if it's piston or DI? If so, then how?

You can take a AR15 calibered in 223, 5.56 and just swap the barrel out with a 300 black out barrel and your rifle will be a 300 blackout.

quote:

Originally posted by lyman:
MULTI simply means it can be used for multiple calibers,

and there are lots and lots of choices

Yep like the big bores 458 socom,450 bushmaster,and .50 Beowulf

quote:

Originally posted by vthoky:
I'll drift my own thread here and ask: If we were looking for piston-driven uppers in .300 BLK, what would SF recommend?

And because I'm still newbie, can I tell by looking at an upper if it's piston or DI? If so, then how?

I don't think anyone makes a piston .300 AAC Blackout upper.

Also, don't waste your time with a piston upper AR, they don't really offer anything over the DI system except maybe a little cleaner in the action, with the draw back of weight, extra cost and proprietary parts.

There are fans of piston AR 15's, that's fine with me if that's what you want to spend money on. Just, it's just not needed, extra cost, weight, parts, and complications with no return.


ARman

quote:

Originally posted by vthoky:
I'll drift my own thread here and ask: If we were looking for piston-driven uppers in .300 BLK, what would SF recommend?

And because I'm still newbie, can I tell by looking at an upper if it's piston or DI? If so, then how?

The is the one I'd recommend:

https://primaryweapons.com/sto...mk116-mod-1-p-upper/

Look at the gas block.

A DI gas block/FSB, will be relatively simple looking and have a bright silver hollow tube going to it, ( look at were this gas tube stops inside the upper to see if it's hollow. ) Also, a gas tube will step up as it runs along the top of the barrel, just before it enters into the upper receiver.

A piston driven upper has a generally much more complex/busy gas block with knobs and such protruding from it, as well as being somewhat larger than a typical low profile gas block on a DI upper. In place of a hollow gas tube found on DI uppers, a piston upper will have a solid rod taking the place of a gas tube.

* Edit to add * I have a billet lower marked 'Multi' that I built up to primarily run 6.8 SPC.

quote:

I don't think anyone makes a piston .300 AAC Blackout upper.

Isn't the MCX available in .300blk? And wouldn't that be a piston one.
I don't follow the .300blk world but I thought I could swap my MCK to .300blk and I wouldn't think that would also be a DI conversion.
I'm in the camp of why on the piston ones as well.

Always start with 5.56.

There's a whole list of calibers in this thread...
https://sigforum.com/eve/forums...0601935/m/5310068334

If you've got a Palmetto lower, I'd match it to a Palmetto upper. In the unlikely event you have problems Palmetto will be MUCH more helpful if both assemblies are theirs.

Plus, Palmetto is nearly giving away complete uppers right now.

I got a 5.56 upper first, then later added a .300 Blackout upper to use with a suppressor.