Well, there’s always the Doc’s take…
"Short barreled 5.56 mm weapons, such as the Colt Commando, Mk18 CQBR, HK416, HK53, HK G36C, etc… offer advantages in confined spaces.
With SBR’s it is best to stick with the barrier blind loads recommended above*, although the heavy OTM’s suggested for long distance shooting will also work. SBR’s can run into rotational velocity issues with some loads, so it is generally best to select faster 1/7 twist barrels whenever possible. Remember, with SBR’s, effective engagement distances are significantly reduced compared to the longer barreled carbines."
*If you have 1/9 or faster twist rate barrel (so 1/9, 1/8, and 1/7 twist):
*** 5.56 mm Federal 62 gr Trophy Bonded Bear Claw (TBBC) bonded JSP (XM556FBIT3)
*** 5.56 mm Winchester 64 gr solid base bonded JSP (Q3313/RA556B)
*** Black Hills 5.56 mm 50 gr TSX loading.
*** The Hornady 5.56 mm 55 gr GMX
NOTE: that these are all true 5.56 mm loads that require a real milspec 5.56 mm chamber, not a SAAMI .223 chamber–be sure to check with an appropriate gauge or reamer.
Most other acceptable LE barrier blind loadings are at .223 pressures including the following …
*** .223 55 & 62 gr Federal bonded JSP Tactical loads (LE223T1 & LE223T3)
*** Nosler 60 gr Partition JSP,
*** Remington 62 gr Core-Lokt Ultra Bonded JSP (PRC223R4)
*** .223 Federal 55 gr TSX (T223S)
*** .223 Hornady 55 gr GMX
*** .223 Speer 64 gr Gold Dot JSP‘s (and identically constructed Federal 62 gr Fusion JSP and Federal XM223SP1 62gr Bonded JSP).
*** The Swift 75 gr Scirocco bonded PT is also good choice, but usually requires a 1/7 twist.
Note that the Barnes all copper TSX bullets are great projectiles and offer good penetration through barriers, however, when first hitting a laminated automobile windshield intermediate barrier, most TSX bullets exhibit less expansion than bonded JSP’s, as the Barnes jacket either collapses at the nose, the jacket “petals” fold back against the core, or the “petals” are torn off; this results in a caliber size projectile configured a lot like a full wadcutter, leading to deep penetration.
SOURCE: https://preparedgunowners.com/2016/01/12/the-approved-list-of-5-56-nato-223-rem-self-defenseduty-ammo/
Unf, only T3 is on this list.