The following is my opinion. Different schools of thought exist on these things, but there are certain things most professionals can agree one what constitutes an Infantry Carbine. Since I am not using the Army or USMC parts pin, but have access to the more extensive civilian parts bin, my examples will look a bit different, not worse in any way though.. ...but in any event, I will try to explain the configuration choices that IMO make up a good defensive rifle/Infantry Carbine configuration for a citizen.. ...Also this is not about whether a given component is "high end" or not.. but simply on how the rifle is configured...which can be done with any "level" of parts. First some pics of rifle I own or have owned in the past, that were primarily configured as generalist fighting rifles, or General Infantry Carbines. What does this mean? Its means not configured as a designated marksman rifle.. often abbreviated as DMR..(which would entail a 20 inch barrel and a traditional optic among other things.)... DMRs need not apply since they or often not very handy... Also a not rifle configured as a PDW , Personal Defensive Weapon. Sometimes also known as trunk guns or truck guns... These are marked by very short barrels sometimes even mags under 30...Their short barrels and at time ultrashort stocks limit their abilities as fighting rifles as some performance considerations are subordinated to their handiness. So I want to present a jack of all trades that can fill a generalist infantry Carbine role This to me, presupposes a minimum barrel...lenght of 14.5 inches.. better 16 in order to get good performance out of available ammo. Example 1: This rifle is very close to what I consider a all around good defensive configuration, good for very short range and out to maybe 300m.. I owned this rifle in the past. -It features a 14.5 inch barrel for handiness. 14.5 inch is the Army's M4A1 Carbine spec. The AK series BTW features 16 inch barrels.. I consider both barrels lengths fine but have a slight preference for 16 inch. This had a professional welded+pinned muzzle brake on it to keep it at NFA free 16.1 inch length. Dont play fast and loose with these rules BTW. This particular barrel is CHF chrome lined but your gear does not have t be this high end.. a "regular" ordnance steel barrel that is nitrided will suffice. - Adjustable stock... this is important to get your rifle to fit your personal ergonomics.. and also what clothes u happen to wear at the time. I prefer in the prone to pull the stock out all the way and when walking to push it in one notch from all the way. -This particular rifle has a less angled pistol grip. A BCM. I like these a lot. The original angle pistol grip for the M16 was designed when doctrine was still closely matched to traditional shooting from the prone. And while the prone is still the best firing position for cover and accuracy its well accepted now that most modern defensive uses occur when standing (or leaning over a hood, leaning against a wall or reflexive fire when surprised while walking, etc) or kneeling. This pistol grip is more ergonomic for that. I ordered a few of them and intend to equip all my ARs with them. - A 30 rd mag... yes this is the proper standard. Why not 40 rd or more? The extra weight doesnt help the rifles handiness and the "chin" of the mag juts out excessive for some firing positions. Then why not a 20 rd mag, wouldnt that be better for the prone? No. In the real world nothing is ever perfectly flat you have to adjust your elbows usually a bit on the high end anyway.. dont worry a 30 rd mag will not keep you from a good prone position... and when exhausted you might like the mag bottom resting on the ground for extra stability (even though its not good for the mag... but when u really need it .. who cares..) - A vertical front grip under a free float rail.. free float rails while aiding accuracy are not mandatory by any means... they come in different flavors ,, the army arsenal picatinny Quad rail, as adopted by Army and USMC, (which I still prefer), M-Lok and others... the main thing is there is a vertical front grip installed and its not too far forward. This is a bit of a personal preference of mine... not everyone agrees with this. A VFG is Army Standard on the M4 but many "cool kids" like to use holds that dont use a VFG grip at all... My arguement for it is, is that its a 80% solution... its helpful to reduce fatigue when walking in the low ready, and also helps ripping the carbine around quickly from the low ready.. Its not the best tool for every single firing hold but an decent one for a great many of them.. Most of us who train have limited training time and ammo budget.. so it may be best to just pick one hold and train with it until its mastered. But again this is a personal preference and not all people whom I respect, agree. - A weapons mounted light. A lot of defense shootings happen at night.. It can be a useful tool if used wisely. - This particular rifle is configured with a muzzle brake instead of a flash hider.. many sport shooters or competitors prefer muzzle brakes.. but for a defensive rifle.. just no.... .. I bought it used with the brake on it. I strongly prefer a flash hider... in this caliber there simply is no reason to worry about recoil... especially not to the extent of being willing to self blind with muzzle flash at night which a muzzle brake might do... and also the muzzle brake acts as a loudener.. not good if you have have to shoot indoors on short notice and dont wear your muffs. They also kick up extra dust when shooting close to the ground. - Electroptics. A defensive Carbine is set up for close to medium ranges. Electro optics such as red dots or holographic weapons sights such as this one ( an EOtech 512) excel at this. Note the postion on the rail far forward. it looks goofy but its the proper set up for this... some push even further to the front. This is another one of my rifles. The famous LWRC M6A2.. but its not about how hi end a Carbine is but this article is about configuration.. No muzzle brake but flashhider, extended trigger guard, Adjustable stock, weapons mounted light, VFG a decent electrooptic mounted forward... This has something important the previous one missed a traditional 2 point sling. One point slings look cool but dont really accomplish that which a sling is supposed to accomplish... Keep your hands free and your rifle out of the way while you, load a vehicle, do work , climb, march while handling a a radio etc etc.. Also on this rifle you can see an extended latch charging handle.. Those are an significant ergonomic improvement over the original design. Every single one of my Carbines have extended ergonomic charging handles like this now. This particular one is a BCM medium The pistol grip has the old school angle (since changed to the more vertical BCM) Both rifles feature back up sights.. flippable magpul... which work quite well and are quite robust... Most folks would say you MUST have back ups sights and for good reason... but I am not really doctrinaire about that... some of the modern electrooptics are more robust than the rifle itself... so IMHO its less of a must-have than maybe years ago..