The handgun is convenient and easy to conceal.
The carbine is more effective but heightens profile.
A carbine is impractical for most circumstances, but for home defense it is the preferred choice if available. It can be practical for some civilians to keep a carbine in their personal vehicle but this may not be viable in many cases.
What might an optimized defensive carbine for the armed citizen look like?
The likely engagement envelope for this weapon would be inside a residential structure, in low light conditions, to be used against close range threats – possibly multiple but no more than a handful.
The armed citizen will most likely have been awakened out of a sleep (groggy) and will be wearing minimal clothing, no gloves, no earpro, no eyepro, and no support gear.
The weapon should be set up to “grab and go”, i.e. an extra magazine mounted to the gun, a light mounted to gun, the optical sight (if used) turned on, BUIS deployed. This weapon should be for the infamous “bump in the night”, ready for immediate deployment.
Extreme precision is not required; reliability is a more important attribute.
Magnified optics are not desirable due to the nature of the ranges involved.
The weapon should have compact overall dimensions to aid in maneuvering inside the home.
The lightest possible weight (KISS/superlight, etc.) is not necessarily a requirement, though weight savings is always desirable if performance is relatively unaffected.
A sling may not be absolutely necessary in a purely reactive situation or in a static defense, but it is a wise accessory when the aforementioned scenarios move beyond the initial encounter. A QD sling is a good option rolled up beside carbine, as is keeping the sling stowed on the carbine.
A suppressor is a good option if overall compactness and balance is not sacrificed.
Ammunition selection should be proven effective against humans yet reduce the probability of interior/exterior wall penetration.
The weapon is likely to be left in Condition Three (cocked on safe, empty chamber, magazine inserted).
Using the above criteria as a guide, an optimized defensive carbine for the armed citizen may look something like this:
- barrel length 10″ to 12.5″
- mil-spec “NATO” chamber and M4 feed ramps
- 1/8 or 1/7 twist rate
- fixed compact or adjustable length stock
- 20 round magazines
- 75 gr Hornady OTM, 77 gr Nosler OTM, or 77 gr SMK OTM ammunition
- dedicated weapon light (examples: SF X300, M300A Scout, Insight WX150 LED, Streamlight TLR)
- compact, lightweight suppressor (examples: SF Mini, Gemtech TREK, AAC RANGER 2)
- lightweight rail, preferably partially enclosing suppressor and/or mounting a handstop to protect from burns
- Boonie Packer Redi-Mag (or BFG Redi-Mod)
- fixed front sight and fixed or deployed folding rear sight
- optical sight (examples: Aimpoint Micro T-1, EOTech XPS) or visible laser (example: Insight AN/PEQ-5 CVL)
- quick deploying two point sling (VCAS w/QD mounts, VTAC-PS Attachment Sling)
Magazines are a failure point for semi-automatic firearms, and historically they have certainly been a failure point for AR-15s. In my scenario I am using 20 round magazines, so probably we are talking about 36 total rounds on the weapon. IMO it's a lot more realistic that the typical home owner may have to conduct remedial action or a reload than it is to suggest that they'd be armed with a secondary weapon to transition to.
I personally recommend the Aimpoint Micro, but I didn't want to play favorites in what I wrote above. There are very compelling reasons to use a 30mm Aimpoint as well.
If bullets start flying inside your own house, odds are high that you will experience the physiological phenomenon of audio exclusion - however short barrel 5.56mm guns are still loud and blasty. A bad guy is probably going to armed with a handgun and will be (hopefully) at least a couple of yards away, so I don't think hearing loss from an assailant's firearm would be a factor. Anyway, you still have the ears of your own family to try and protect. As I stated above, a suppressor is a good option if overall compactness and balance is not sacrificed.
The final layout of the weapon is not nearly as important as the process which determines it.
When one clearly defines one’s mission (whatever that may be), subsequent gear and training questions usually fall into place.
People need to make realistic, informed determinations of their needs and suit their gear (to include weapons) and their training accordingly.
The intent of my post is not to advocate for the carbine for home defense. It is instead an example of a methodology if you've made the determination that a carbine is the right tool. It is made in a vacuum, with out consideration of local laws or attitudes of juries. It is, as stated, what an optimized defensive carbine for the armed citizen might look like.
~ Jay C
edited to add: Implied in the above is the necessary training and practice in order to employ the carbine effectively in an indoor environment. No one suggests not "honing the real weapon in the system".
Regarding those who may suggest a fixation on the gun and "stuff" that you bolt to it: once again mission should drive the gear train. If you had a mission of fighting inside a structure and you were presented with two weapons:
M16A2
Mk18
Which would you choose?
You don't have to answer that. Point being, people need to make a realistic, informed determination of their needs and suit their gear (to include weapons) and their training accordingly.
The above is not "The Law as Told By Jay"; it is simply an expression of some opinions that I've formed through my training and experience with several very good instructors. Please feel free to discuss and disagree!