Whether you call them blue guns, rubber ducks, decoy guns, or whatever, solid polymer practice guns can serve a multitude of purposes while helping to hone perishable skills on the cheap as well.
What are they?
The military and police have for generations used dummy guns to train new recruits. Often called "Quaker Rifles" back in the 19th Century, they were typically wooden rifle stocks affixed to a solid receiver and barrel. They were made from stocks of surplus guns and piles of damaged weapons no longer safe for service. In some cases, drill rifles and pistols were made from once-working guns that were pulled from service. Dewatted with a steel rod welded inside their barrel and bolts or firing pins sheared off, these guns are still seen in the hands of military school cadets and ROTC units.
Today its far cheaper and efficient to mold solid replicas out of polymer that very accurately capture the size, dimensions, and surface controls of modern firearms of just about every popular model.
Who makes them?
The two biggest blue gun makers are Rings (who makes about 10 different XD sizes), makers of a line of blue guns and ASP, who makes a comparable series of guns in red (beware though that ASP does not currently carry an XD rubber gun) .
Blueguns even makes some pretty neat variations, such as this SPRINGFIELD XDS 3.3 w/C.T. Laserguard
While the sites themselves have some functionality, you can shop around online everywhere from police supply sites like Galls to online marketplaces like Gunbroker and eBay. Typically, you can luck into these anywhere from $20-$50 and it's likely they have your model or one very similar.
When practicing movement drills, weapon presentation, holstering, close combat, and other evolutions that do not require a loaded firearm, there is no substitute for safety. This is the whole reason for being on a replica gun.
Much of your training regimen for the use of your handgun does not involve range time and making holes in paper. Draw practice and presentation drills build all-important muscle memory for the modern shootist. There is no substitute for this type of sweat equity put into knowing your firearm instinctively.
The great Delf A."Jelly" Bryce, was possibly one of the greatest modern gunfighters in law enforcement history. He was involved in no less than 19 police gunfights and came out on the winning end of each of them against some of the worst criminals and known cop-killers of the 1930s. Besides his own obvious natural talent, he honed his skills on relentless drawing in front of a mirror.
In addition, if you are serious about home defense, you need to spend some time moving around your house to make sure you have the skills and experience to know where your cover and concealment is while standing in your hallway, or how to best negotiate the laundry room door while not flashing your muzzle over your stomach. This is where a training barrel can come in handy.
Tip-- also, don't do this when the kids are hosting a sleep over or the mom in law is there for dinner. Some things are best done when the house is empty.
Keep that training safe with a replica.
When you actively carry a handgun for self-defense and pick up a new holster, the worst thing you can do is put your loaded firearm in it fresh out of the package and roll out the door. You aren't sure how the holster wears, how it moves when you get in and out of a vehicle, if it rides too low and the grip tucks under your waistband, or worse, if it allows the gun to fall out and skitter across the ground if you bend over.
With that in mind, there is nothing smarter than seating that replica gun in the holster and spending the first 20-30 hours that you carry the rig while you do your regular routine around the house. Its then that you realize if the holster is going to work for you or not out in the real world.
However, they do make a good training tool that would leave you hard pressed for a better way to spend the price of a cheap dinner on.