.300 BLK uppers and 5.56 uppers interchangeable, right?

[TheRealJQP]

In terms of proper function, if you have a 5.56 AR, and a .300 BLK upper, you can swap the .300 upper for the 5.56 upper and you're G2G, right?

 

[dcloco]

Yes.

Not uncommon to have one dedicated lower for multiple uppers.

 

[TheRealJQP]

Right, just wasn't sure if a .300 BLK upper would be fully compatible with a standard .223/5.56 lower.

Thanks.

 

[P.B.Walsh]

Correct, only the barrel is different.

 

[Arizona_Mike]

Yes but you may want to run a different buffer and some AR mags can be finicky.

Mike

 

[Ibmikey]

If your 300 BO is for firing supersonic and your lower uses a standard buffer you should be ok. If running suppressed fire components such as buffer may need adjustment. Be sure to dedicate a BCG for each separate upper.

 

[justin22885]

im noticing they even make 300 blackout barrels now for HK93/HK33 rifles, as well as theyve been making them for AKs for a while.. just a barrel change on any rifle

 

[dh1633pm]

Like said above, you might need to work with the buffer a bit. Just test with your lower of choice and see how it works with the loads you shoot.