Here is a rundown of some of the best choices, in alphabetical order, not ranked by any other criteria.
The first commercial bullpup-style rifle ever adopted for military service on a wide scale, the Steyr AUG has been around for almost 50 years and has been much-updated from its original format, with the A3 M1 being the most current. What has stayed the same, though, is that a compact 5.56 is awesome (AUGsome?).
Borrowing its name from the revolutionary LMG of WWII fame, the CZ BREN 2 MS is a piston-driven rifle chambered in 5.56 NATO that feeds from STANAG (AR15/M4) magazines. This is an incredibly robust system that is excellent for tactical use, property defense, or range time. You really ought to Czech it out if you haven't heard of it already.
The Spanish CETME series of rifles were some of the first roller-delayed infantry arms to emerge from the lessons of WWII, going on to evolve into the world-famous HK G3/41/91 series. Using the same style of uber reliable action, the CETME L series in 5.56 appeared in the 1970s and served NATO troops for a generation. Today's commercial semi-auto variants made by MarColMar are faithful to the original but have been significantly upgraded. Plus, they just flat-out look great and, once they are gone, they are gone.
The modernized Galil ACE is based upon the reliable mechanism of the original Galil rifle first developed by IMI in the late 1960s. Still offered in a 5.56 NATO model, the latest generation, as it is descended from the same line as the legendary Russian AK-47 and the Finnish Valmet RK 62, doesn't use an AR-style buffer tube so you get the benefit of a side-folding adjustable telescoping buttstock with a two-position removable comb. However, it does use AR-style mags, so that's a win.
Sure, they aren't as flashy or exotic as some of the other offerings on this list, but the Ruger Mini-14still fits the bill as a non-AR .223 semi-auto modern sporting rifle. Best yet, they are often still available for consumers trapped behind the lines in anti-gun states due to being "featureless" when compared to other MSRs. Plus, if this rings a bell: "In 1972, a crack commando unit was sent to prison by a military court for a crime they didn't commit..." then you may have a serious affinity for the Mini-14 aesthetic.
Created to fill a need for an adaptable, modular, and modern rifle for the special operators of USSOCOM, FN's SCAR series has been traveling the globe with quiet professionals for over a decade in light (SCAR 16), heavy (SCAR 17), and sniper (SCAR 20) variants. Heck, they are even accurate enough for bearded fat guys with minimal training to use in zapping targets from helicopters with no problems. For fans of 5.56, the SCAR 16S is the ticket.
Florida-based KelTec cut its teeth with small, polymer-framed pistols, branching out in 2001 with the SUB-2000, a folding pistol caliber carbine that weighs just 4 pounds. Upping the ante a bit, they used the same rough concept for a lightweight "Sport Utility" rifle in 5.56/.223, the SU-16. Yes, it folds. Yes, it takes AR mags. Yes, it weighs less than 5 pounds. Yes, we usually have them in stock.
Another top-shelf bullpup in the lineup is the IWI Tavor X95. Hailing from Israel, where they have proven themselves and become popular with users around the world, the X95 features a compact design that is rugged, lightweight, and accurate. Best yet, it is ambi, which means southpaws who are looking for a dependable 5.56 carbine could do far worse.
These guns, due to their rarity, at this point are more the realm of collectors' pieces rather than daily drivers, but they are still very capable if needed – and turn heads at the range. Be sure to check them out if you want something really special. Here at Guns.com, we are always interested in these types of guns and frequently have them available for the discerning black rifle enthusiast.