Help me please

I remember a while ago when watching a Movie, that a guy had a gun that could be used as a pistol and then later on as a sniper rifle.

Does anyone know what this weapon was or is? If it is real. I've searched the internet but found nothing.

Thank you.

Sounds like they used modifications, like a detachable butt stock for stabilty, a scope of choice and probably a longer barrel for that whole accuracy thing. It wouldn't take much besides 5 min or less to convert a pistol to a half decent modified rifle. The biggest problem would be range, a pistol cartridge would not be very good beyond 50 - 100 meters. A rifle cartridge would be needed for greater range. I imagine this thing was a "Hollywood" glamor prop more than an actual weapon. but the idea is possible, multiple caliber firearms exist, just need to swap out bolt types and barrels.

As for a particular pistol, none that I am aware of.

Odium,
There are already numerious pistols on the market that are in what are normally rifle calibers. The Thompson Contender comes to mind. Also the Remington XP 100 series or the Savage arms Striker series. Most of these are single shots. The M16 also comes in a extreamly shortened version with no but stock..almost pistol or machine pistol looking.
Skilled gunsmiths can modify almost anything to suit this purpose..some being more readily modifiable by inherant design ..of course. The most skilled can design and build from scratch.
Also ..scoped pistols are not new ...lots of scoped pistols at the shooting range I use. I know a handful of people who can shoot one of these fancy pistols out to three hundred yards..quite a feat. Orangetom.

As Orangetom said, there are loads of suitable weaps on the market. H&K make a few, Colt make a few more, as does AK but really, these are short barrelled carbines.

The Skorpion also springs to mind but the H&K MP5K is much better.

Then there was the Israeli Uzi and the Spectre.

Never heard of the Spectre? It's the handgun used by Robocop and it's very, very real. 3 round burst facility. Really cool weap.