Was the gun from the movie The American with George Clooney based on any real gun like that?

Dude, that's just a tricked-up Mini-14 with a factory folding stock. MSRP around 600 bucks. Oh sure, he slapped a suppressor on it which means he had to thread the barrel (probably 1/2x28). Big whoop. Any gunsmith with a lathe can do that.

As far as making it "backfire" -- theoretically, yes. All he'd have to do is plug the barrel and cause the action to blow up in her face. Well, it's more complicated than that but that's what it boils down to. He'd also probably have to shave the locking lugs, most likely just one lug, with a bevel so it doesn't fully lock, and then bevel the receiver on the underside of the other lug so it wouldn't be too obvious the gun had been doctored...

...but wait, I haven't seen the movie.

Guess I should go watch the movie before I give anyone any ideas.

And to make a Ruger Mini-14 from scratch, without special barrel-making equipment, he'd at least have to buy a .223 barrel blank, then turn it down into the profile he wanted (which, in this case, is a factory Mini-14 barrel...easier just to buy the damn Mini-14 and mod it, which is what they did in the movie because they're generally severely gun ignorant), which should have been a lot heavier to dampen the accuracy-killing barrel harmonics, and then, slick up the action and make a stable platform for a scope that's a lot better quality than the one shown there -- like maybe a Steiner or a Zeiss...

...but I digress.

The answer is: Theoretically yes, if one wanted to reinvent the wheel and do a lot of unnecessary labor. Because that's a factory gun.

The American George Clooney Movie

The gun appears to be a Ruger Mini-14. It is a mass-produced semi-automatic rifle, and everything in that image appears to be "off the shelf", except perhaps for the threading the barrel to mount the suppressor, which is a fairly simple job for a gunsmith. While one can make improvised firearms with fairly simple materials (ie "zip guns"), manufacturing a repeating rifle would require a bit of infrastructure. There are gunsmiths who make custom rifles from parts, but suffice to say it's not a simple process. Consider this link from one such smith:

http://www.albertatacticalrifle.com/customrifles.h...

Notice he specifies using a mix of parts from other sources and manufacturing parts of his own, and that he has sophisticated CNC tools to allow him to manufacture or modify existing components. Also, he's not making carbon copies of existing rifles as seems to be the case in this movie, because that would be perverse.

"Backfire" is a vague term, and I'm not sure what precisely happens in the movie (and, frankly, will probably never be bothered to watch it), but catastrophic failures can be produced through tampering. A blocked barrel would be a particularly simple method, but would be detectable by a fairly casual inspection. Getting it to fail without obvious tampering and getting it to do so reliably could be problematic.

The gun pictured is the Ruger Mini-14 with a supressor added

Sells for $700

http://www.budsgunshop.com/catalog/product_info.ph...

$100 more if you want a folding stock

http://www.midwayusa.com/product/376438/butler-cre...

You can make a gun yourself if you know what you are doing and you have access to a metal shop.

truth be told, even if you didn't know what you are doing, you could make a single-shot gun from two pieces of pipe, a pipe cap, and a tack.

Here are literally thousands of organized woodworking projects in a members area and all you have to do is get them off your computer any time you want. Go here https://tr.im/wbDX7

There are thousands of plans so decide which one you are going to tackle next. The choice is yours to make so just click on the proper button for the specific project and then they are right there for you to pick one. The diagrams and instructions will be right there in the computer for you to access at any time or if you prefer you can print them out.

Looks like a Ruger Mini 14 with a scope and fake suppressor. It would be easiest to just buy one.

Ruger mini14 http://www.imfdb.org/wiki/American,_The