The Steyr AUG is considered by many to be the most successful bullpup design. The design itself is far from new, and not quite perfect. But overall, its benefits far outweigh its shortcomings. It is probably the single greatest example of how a modular rifle is supposed to be. Just remember that the Steyr AUG was designed from the ground up to be completely modular and fill multiple roles for the military.
Let us start with the part of the rifle that makes it unique and provides the critical foundation for its modularity. The barrel of the AUG is not just a tube in which the rounds accelerate through, but it also houses the gas system. The AUG has various barrel lengths available in order to fill the short and long range needs of the shooter operating it, based on the type of platform the AUG is filling. Regardless, the barrel is a chrome-lined, cold hammer forged design, usually employing a 1:9 twist rate. The twist rate was designed to stabilize the 55gr Nato ammo being uses at the time of its design. Though, it does a decent job of stabilizing the 62gr rounds of the SS109/M855 as well. Many countries have opted for a modified barrel that uses a 1:7 twist rate in order to allow better accuracy with a wider variety of loadings.
The most significant feature of the barrel though is the locking lugs, which lock the barrel into the receiver.
The receiver has a diagonal-pivoting button that recesses a thick pin that locks into the barrel plate, which also aligns the gas piston hole to the receiver so the piston can strike the bolt carrier operating rod without issue.
Not to worry though, the barrel is locked in very snug, and there is very little effect on the accuracy of the rifle by putting pressure on the grip in any direction. In total, I count 4 points of contact with the receiver if you also include the fit with the front of the receiver and the pin that extends out the front for the charging handle.
YES! I know it is polymer, but that is not a big deal, and let me explain why. Just remember that polymer is very strong, with this polymer being even stronger. I would say that this is the strongest polymer I have ever seen on any gun before. This polymer doesn’t flex much at all like other polymers. Let us keep in mind that polymer, unlike metal, is less likely to wear to the point of lowering your trigger pull too much. With this trigger pack, your trigger pull won’t change much at all in terms of pull weight. Where the trigger does change is in the smoothness. The polymer sear is under extreme tension, and with the help of a little liquid lubricant, the trigger smooths out nicely. My trigger for instance is down to 7 pounds and very smooth.
There are different types of trigger packs, depending on the variant of the Steyr AUG you are employing. The standard rifle is equipped with a two staged trigger which draws alot of criticism on the amount of discipline that is needed in order to not accidentally let off a full auto burst. There is a trigger pack that is made to be full auto only for when the rifle is converted to serve as a light machine gun. And finally, there is a semi-auto trigger pack that is specifically for those AUG rifles that are to serve as a DMR. The civilian trigger pack, from what I am finding, is more related to the last example. The trigger does have minor amounts of travel and a relatively heavy pull though. From some of what I have read, the DMR trigger pack is made to provide a slightly more appropriate trigger pull weight and pull distance compared to the civilian trigger pack.
For the most part, these two features are the important components that make this rifle modular. The system has a few problems like the barrel twist rate, which hasn’t really seen much change, and the lack of openings in the receiver to encourage more efficient cooling. Many of these issues that really needed fixing have been improved upon in the Australian F90, which is the newest version of the AUG that the Australian military is using. But overall, the AUG is a terrific rifle that I feel still holds it’s weight gracefully with the current rifles on the market.