How short we talking here? And I assume we're talking .223 Rem/5.56×45mm NATO?
Hornady claims that this particular round is optimized for 10.5"-11.5": http://www.hornadyle.com/produ...6-nato/75-gr-tap-sbr
I personally just use Gold Dot 62 gr and call it good, being aware that it'll have a more limited range for optimal expansion, although I'm running 10.5" and 11.5", and not the super shorties like the PWS MK107, LWRC PSD, or H&K G36C. FWIW, Speer does claim that "Gold Dot rifle bullets are optimized to ensure expansion out of barrels down to 10" at a wide variety of velocities out to 200 yards".
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.
Here's the beginning of Doc's post:
For LE Patrol use, where there is a high incidence of potential engagements around or involving vehicles, ammunition that is able to effectively penetrate intermediate barriers, particularly vehicle glass is critical. The best LE 5.56 mm/.223 loads for intermediate barrier penetration using 1/9 and faster twist barrels are the 5.56 mm Federal 62 gr Trophy Bonded Bear Claw (TBBC) bonded JSP (XM556FBIT3) and 5.56 mm Winchester 64 gr solid base bonded JSP (Q3313/RA556B) developed for the FBI, along with the outstanding new Black Hills 5.56 mm 50 gr TSX loading. Another acceptable 5.56 mm loading is the Speer 55 gr Gold Dot JSP; the Federal 5.56 mm 62 gr Mk318 Mod0 (T556TNB1) is also a potential option. 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 .223 55 & 62 gr Federal bonded JSP Tactical loads (LE223T1 & LE223T3), along with loads using Nosler 60 gr Partition JSP, Remington 62 gr Core-Lokt Ultra Bonded JSP (PRC223R4), .223 Federal 55 gr TSX (T223S), and the .223 Speer 55 & 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.
If running 1/12 twist barrels, stick with the BH 50 gr TSX, Fed 55 gr TBBC, Speer 55 gr Gold Dot, or Fed 55 gr TSX. NONE of the fragmenting 5.56 mm OTM bullets, even the heavy 75 - 100 gr loads, offer acceptable performance through automobile windshield glass. Contrary to what many believe, M193 & M855 FMJ are not very good against glass; the best military 5.56 mm load against glass is 52 gr M995 AP, followed by the 62 gr Mk318 Mod0 OTM and 70 gr Optimal "brown tip" OTM. In those situations where intermediate barrier penetration is not a critical requirement, for example LE urban entries or long range shots in open conditions, then OTM, JHP, and standard JSP loads can offer acceptable performance. For 1/7 twist barrels, the Hornady 75 gr OTM, Nosler 77 gr OTM, and Sierra 77 gr SMK OTM are all good choices. The experimental BH loaded 100 gr OTM exhibits impressive fragmentation, even at relatively low velocities, however while capable of shooting out to 600, it is optimized for 200 and under. If stuck with 1/9 twist barrels, the heavy 70+ gr loads are not universally accurate in all rifles and the 69 gr SMK OTM, the 68 gr Hornady OTM, the Winchester 64 gr JSP (RA223R2), the Federal 64 gr TRU (T223L) JSP, Hornady 60 gr JSP, are likely to run accurately in the majority of 1/9 twist rifles. Again it is critical to keep in mind that the above loads fail to offer adequate penetration through intermediate barriers.