You may be familiar with the doomsday clock, if not, the basic premise is that we are a certain amount of time away from a global catastrophe. For several years now, about three minutes to complete global annihilation. Yes we gain some time and lose some time, but we typically ride that 3 minutes between life and death for our entire planet. When and if it happens, we don't know for sure exactly. We don't know where, or what. And if it does happen we may never know why. What is clear, with so much uncertainty and obscurity nearing total global darkness is the need for a weapon and training methodology that will provide for our defense needs whatever they happen to be. In such a scenario, we should probably assume the worst. We are alone, in a violent and unforgiving place and need to cover allot of ground rapidly. This may mean abandoning and transitioning to multiple types of transport when one fails, or becomes inadequate due to road conditions, horde mentality, or changes in terrain. This may also mean covering a multitude of transitions, be they urban environments, industrial, indoor and outdoor, wooded or open. And at all hours, because we don't know if the situation will dictate night or day travel for safety reasons. We will quite possibly also need to carry allot of ammunition. A PDW, or personal defense weapon may be the exact niche for this type of situation. And this is how I would approach this specific firearm. Basing much on the number " 3" i am considering beginning the build with an Aero precision 8 inch .300 AAC upper reciever with an adjustable bolt carrier group. (A barrel at or under 300mm in length or roughly 10") The 300AAC is optimized for this barrel length, even with a 8" suppressor, the full barrel length won't be much over 16" , the 300AAC with supersonic ammo has ballistics nearly identical to the 30-30, or 7.62x39mm AK/AKM, And with subsonic ammo, ballistics very similar to .45 ACP. This makes the weapon very flexible for hunting applications, shooting through barriers, and use as a general purpose cartridge. At the muzzle end, is an IMACS muzzle adapter, to allow installation of solvent traps without being forced to remove your muzzle device. while it is illegal to install a vertical grip on your rifle, the TMACS, inc. "Sling ding" can be used as a grip, monopod, or barrier rest. The SB tactical PDW brace uses a full sized buffer tube, and retains all the parts commonality of the standard article unlike some other systems. the fostech "echo 2" is a full auto simulation device still available for purchase. Unlike the first version, it allows you to use a standard carrier instead of the modified fostech one. a high quality prismatic sight such as this STEINER 3x illuminated optic would be a good choice. Allowing the user to engage targets accurately at distances up to roughly 300 meters. If the battery fails, prismatic sights have etched reticles not dependent on batteries. Of course a set of back up sights, flashlight and a few other things may be required to tailor it to the individual. My arbitrary criteria: Weighing less than 3KG (6.5 pounds) Has a barrel under 300mm (10") Can print a group size of 3" at 100 meters or better with good ammunition (aero precision uses the excellent ballistic advantage barrels) for reliable accuracy on head sized targets or even brain stem shots at 0-100 meters. And minute of man accuracy to 300 meters. (Roughly 9" circle at that distance) It feeds from a 30 round standard magazine. And it would not be out of the question to carry ten magazines for a total of a 300 round loadout. The 3 minute to midnight drill. From a distance of 3 meters, fire 3 rounds on 3 targets in a tactical sequence from the standing position. Next run back 30 meters, fire three rounds on each target for a total of three rounds from the kneeling position. Next run back 100 meters, fire 3 rounds on three targets from the sitting position. Finally run back 300 yards/meters and fire 3 rounds on 3 targets from the prone position, for a total of 30 rounds. To score yourself try to complete the drill as fast as possible, every round on target whether lethal or not counts, for each hit subtract 1 second. For every miss add a second, to/ from your overall time and try to beat 3 minutes. Reload from the prone and repeat the drill advancing. This may seem like a silly drill, but, you can mix it up with a few things to make it more challenging and interesting. You can change at what point to fire only 3 rounds, on three targets, 3 on one target etc. Reduce the capacity of your magazines -forcing you to reload while on the move, or while engaging targets. Insert a few dummy rounds for malfunction clearance. Modify or add cover for shooting around barriers, right or left handed. When you retreat and turn to fire on your first run , you can simulate a "bill drill" or "el presidente" When advancing on your second run, you can turn periodically and walk backwards to make sure no one is behind you. You can add a vehicle to the mix, and simulate fighting your way to it. I.e. do the first course of fire from short range, then run to the 30 where your vehicle is parked, retrieve your vest, or other piece of kit, drive, etc. Sorry if i this is a repost!