"As near as I can tell, people think a shotgun is the best home defense weapon on the theory that (1) pumping the action makes a noise that will terrify intruders; (2) you don't have to aim it; and (3) anyone could shoot it." Man User you said a mouthful there my friend. The shotgun is one of the most misunderstood weapons out there and, as usual, pulp fiction, Hollywood action films, and folklore are to blame, mainly.
For what my opinion is worth, and this is
strictly my opinion here folks, I essentially agree with User's points 1 and 2. Point 3 is a training issue and while the average person, regardless of sex, will find full-power 12-gauge buckshot or slugs very unpleasant to shoot, they can, IF WILLING, get used to it. A 20-gauge is a much better choice, generically, than a 12 and only slightly less effective as an anti-personnel weapon.
Another problem to consider is "short shucking" a pump action gun. This means not "pumping" the action all the way back and forward properly…it jambs the weapon. This is a common occurrence amongst excited rookies and experienced alike.
Home defense weapons should be kept simple (as should all personal weapons) and not exceed the level of the least trained user in the household. Unless everyone is comfortable with a pump, a double barrel a.k.a. coach gun is a good and reliable alternative, preferably in 20-gauge. With minimal familiarization, anyone between 8 and 80 can use one effectively and two sure shots are better than six or eight "iffy" ones in my book.
Instead of me fumbling my way through an explanation of the useful (combat) ranges of the shotgun and it's loads, I have an excerpt from an article entitled "Some Thoughts on the Combat Shotgun - By John Schaefer". This can be found on
Fr. Frog's Site. Don't laugh, aside from the fact that he's a dyed in the wool MTer and Cooper-phile, there is much knowledge there.
The Zone System - While the use of sights will enable a target to be hit, a method is needed to help determine the optimum engagement distances for the ammunition used. The zone system sets up bands of weapon performance versus ammunition selection. The first or "A" zone extends from the muzzle to about seven to 10 yards, where the pattern has typically expanded to between four and seven inches. Within this range the shot charge is effectively a single projectile and it is quite easy to miss a human sized target unless sights are used.
The "B" zone extends from the end of the "A" zone to that range where charge of buckshot has spread to about the width of the human torso (about twenty inches). This occurs at a range of between twenty to thirty-five yards for most weapons. Since the shot charge is spreading out the pattern must be centered to effectively turn off an assailant. While hits can be obtained without proper sights, it is just as fast and much more positive to do it with sights. At the course that I attended the maximum range for the "B" zone for a given ammunition was determined by the range at which the shotgun would consistently knock down a 10 inch diameter steel lollipop target with the buckshot used. (One student's shotgun would consistently drop the target at 35 yards and about 50% of the time at 40 yards! That's patterning!)
Past end of the "B" zone, at thirty-five yards or so depending on the individual weapon, even with modern buffered loads and hardened buckshot the shot charge usually spreads so much that the majority of pellets may not strike the target that is aimed at. This area is called the "C" zone and this is where the rifled slug comes into play. At the course that I attended one of the techniques taught is a "select slug" drill that teaches the rapid switching to a slug round with a shotgun loaded with buckshot when a C zone target appears. While the approximate distances of the zones can be memorized, many of the students used the width of the thick ghost ring system front sight blade as a reference for the B/C break point but once practiced a couple of times you get a feel for when it's time to switch and it becomes automatic.
Some folks may comment at this point, "Why not just use slugs for everything and forget about buckshot" and some folks actually do that. Unfortunately, there are a couple of flies in the ointment with this approach. First, the use of buckshot is mandated by many organizations with slugs reserved for "special" use. Second, slugs will shoot clean through most soft targets so they must be employed carefully for general use.
The biggest problem with both buckshot and slugs is that their performance is highly individual weapon dependent, which brings us to the third principle.
Ammunition Selection - Several noted gunsmiths who are familiar with shotguns have stated that the patterning or grouping ability of shotgun barrels is 1/10 gunsmithing and 9/10s magic. Barrels with effectively identical internal and external dimensions and chokes will give widely varying performances with different shot sizes, loadings, and brands. This is especially true with slugs where a barrel can show a three to five inch difference in group size simply by changing the brand of slugs.
Because the performance of a given barrel is so dependent on the particular ammunition trying to document patterning or group testing is a waste of time. However, using the same brand of standard 00 buckshot in a variety typical unmodified riotguns I have observed 25 yd patterns ranging from 4¾"(!) up to 25", and 5-shot slug groups using standard Foster type slugs ranging from slightly under 3" to over 7" at 75 yards.
The current "reduced recoil" Federal and Remington "Tactical" buckshot loads give greatly reduced pattern diameter in just about every weapon they are fired in because of the lower pellet deformation. However, there are always exceptions. Thus, it is extremely important to zero and pattern your shotgun with the actual ammunition that you will be using. This will allow you to determine the performance of and the appropriate zones for your combination.
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With all that said and done, the shotgun,
properly applied, is the most devastating close combat weapon available. A
suitably trained individual can literally dominate an area out to 125 yards range and then some. Handguns and many rifles don't even come close to the terminal ballistics of a shotgun.
There are more than a few reasons why the combat shotgun has been around since the days of the flintlock blunderbuss. It simply has its limitations, as does any weapon.