williamlayton, The standard recoil spring guide keeps the recoil spring from kinking during slide movement and uses a conventional recoil spring cap. The full length guide rod uses a recoil spring cap that has a hole in it so the guide rod will extend when the slide moves to the rear. The full length guide rods are mostly a hype. They don't make the gun function any better nor do they improve accuracy. They are a pain in the butt to remove when you field strip the gun for cleaning. Also, the full length guide rod prevents you from doing a press check. A press check is where you place your thumb in the front of the trigger guard and fore finger on the recoil spring cap then squeeze your fingers together. This will open the slide so you can see if a round is chambered.
Bushing length is related to barrel length. A standard length bushing is used for a 5" barrel. The short bushings are required on Commander sized guns (4 1/4" barrel) else the bushing will bottom out on the frame and prevent the slide from moving fully to the rear. There are all sorts of bushings available. They must be matched to the different barrel contours and lengths or they won't work properly. Much of the gun's accuracy potential comes from how snug the bushing fits into the slide and how snug the barrel fits in the bushing. A loose fit will totally destroy accuracy and a tight fit can bind and cause feeding malfunctions.
A few companies have come up with a barrel design that doesn't use a bushing at all. This is a poor choice because the blunderbus barrel seats directly in the slide. Any wear will destroy accuracy and would require replacing the slide and/or barrel. This is a big complaint with non-1911 type semi-autos such as a Ruger P series or other non-bushing guns.
The plunger tube contains a spring with a plunger on both ends. The front plunger acts as a holder for the slide lock. This keeps the slide lock from accidentially locking the slide back until it is purposely pushed up by the magazine follower after the last round is fired. The rear plunger acts as a detent for the thumb safety. Without it, the safety would not work properly and could fall out. Some guns, such as a SVI, have the plunger tube cast into the frame. Most other 1911s have a removable plunger tube that is staked in place by two rivet-like posts that extend into the frame. The plunger tube is required and must be tight against the frame, else malfunctions will occur.
Mainspring housings come in several styles. There are straight ones, light, medium and full arched ones, and housings with a built-in magazine well guide. They all make the gun function the same but accuracy will be best when the mainspring housing fits your hand. Many guns come with polymer MS housings. These work OK and are a few ounces lighter than steel MS housings. I like the gun's balance better with a steel MS housing.
There's a ton of aftermarket goodies for 1911s. Some are value added and some are just a way to spend money.
