[Vince Ferrer]

Show me a printed barrel that can stand 50,000 CUP pressure on a sintered metal printer. You can't. It would fly apart after 1 shot.

I don't have any examples of that part specifically, but there is a lot of research being done on metal printing, since there is a lot of interest from aerospace. Instead of just sintering the parts together, there is other post processing now to make the parts stronger. Here is one example:

ExOne Metal Printing Process

Also, the part can probably be cast metal, so we could use a sand printer to create the mold and just cast it:

ExOne Sand Printing Process

Keep in mind that a person doesn't have to completely recreate a commercial model in its exact specifications. If a part needs to be stronger because the printed material is weaker, the engineer may just need to make the critical part thicker.

[Manta]

Sintering From Wikipedia, the free encyclope Sintering is a method used to create objects from powders. It is based on atomic diffusion. Diffusion occurs in any material above a Particular advantages of the powder technology include: Very high levels of purity and uniformity in starting materials Capability to fabricate high-strength material like turbines

[donaldo]

Speaking of firearms and machine guns, let’s hear one massive cheer for that greatest of gun inventors and designers, John Moses Browning, the Mormon from Ogden. I was stunned to learn that he designed (among many, many others), the Colt 1911, Colt Woodsman .22, Browning Superposed, Winchester 1892 lever action, Remington 870, Ithaca Model 37, .30 & .50 machine guns, Browning .303, etc.

http://www.americanrifleman.org/articles/history-john-browning-guns/

http://www.youtube.com/watch?v=TZxKOBmO4aU