If the movie was from the 70s or early 80s, or older, then it's probably what Steve said, some kind of heavy-barrel custom S&W (cylinder latch looks S&W-ish). However, a bit later, S&W did make a few L-frame .357 magnum model 686 revolvers with long, 8 and 3/8ths inch barrels. It's kind of a weird camera angle, but I think it's one of those. They aren't very common, and they weren't released until the mid-1980s (estimate?), but they are out there. I do think it's a later model weapon, as the grips look like they are Hogue rubber mono-grips (screw enters from the bottom), and I don't think they were available until the late 80s or early 90s.
Here's a link to an auction for one, with photos. Long barreled sucker .... could double as a jack handle in a pinch.
Item:7181024 Smith & Wesson 686 Combat .357mag 8 3/8 inch bbl For Sale at GunAuction.com
"Placement is power" -- seen in an article by Stephen A. Camp
(RIP, Mr. Camp; you will be remembered, and missed)