Run Lola Run.
Back when gun hobbyists were more wont to use toxic chemicals, it was common to clean a badly leaded bore by filling the bore with mercury, plugging it, and letting it sit overnight. Next morning, pour out the mercury, et voila, a lead-free barrel. So, we’re looking at a fairly quick process.
Relatively little amalgamation would have to take place to render the cartridges useless for sniper purposes. Snipers are all about consistent performance from their equipment. Cartridges that don’t all shoot to the same point of aim for which the sniper sighted his weapon are not up to the task; especially when you are talking about a marginal caliber like The Jackal used. He needed to make a kill, basically with a single shot. He had to know exactly where that bullet would go.
Plus, how was the Jackal so sure he’d find a guy at the Turkish bath who’d take him back to his place?
“Go back to my place? I got a wife and kids! Why do you think I come here?” 
He was extemporizing – the rapid response of the French to his changes lead him to anticipate that his new disguide wouldn’t last long. In the book, he had stolen a second disguise (Marty Schulberg, a New York college student) that he used temporarily. He then hit upon the idea of finding a homosexual companion and taking over his place. It was much more blatant in the book – The Jackal dressed up in an obviously gay way and went to a gay bar, so there was little likelihood that a pickup would bring him home to a straight family (although he’d have to find another place if the pickup suggested a hotel – he was doing all this to avoid hotels). So it wasn’t that chancy at all.
For the film, they had to telescope the action. andm it being 1971, they had to suggest the gay pickup – things were cagier in cinema, even as recently as that.
Even gayer than the ascot he wore during the film? 
Going back to the OP, at least in my experience, any answer other than The Bourne Ultimatum is wrong.
Another vote here for Shoot 'Em Up, the movie has maybe 10-15 minutes of talking out of an 85 minute running time.
Yup. Read the book.
Of course, if Forsyth got explosive bullets wrong and image intensifiers wrong, I wouldn’t be surprised if he got early 1960s gay garb wrong, too.
Edward Fox at that age would’ve looked gay no matter what he was wearing.
I’m not much of a reader, but this sounds like a book I’ll track down, especially since the film was kickass.
Hell, the average action flick at least pauses for the obligatory sex scene; Shoot 'Em Up blasts its way through that one, too! :eek: 
Well, if he was running away could have joined the French Foreign Legion.
Oh, wait!
Smokin’ Aces is pretty quick, too.
I always thought that “Mysterious Island” (1961) careened very quickly from one action set piece to the next.
La Femme Nikita, Payback with Mel Gibson, and the recent remake Poseidon all move along at a pretty brisk pace.
The scene where the explosive bullet is tested (on a melon) is one of the most impressively disgusting non-gory vividly realized things I’ve ever seen. Love that scene; love the movie.
I was exhausted after watching Black Hawk Down.
I was a teen when that movie first aired on TV. One of my classmates, who had also seen it, promptly swiped some mercury from our high school chemistry lab and tried to re-enact the melon scene with his Remington .22.
I wasn’t with him when he constructed the bullets, but I was present when he fired them. He fired from such close range that I can’t say how much accuracy was degraded. The results on target were pretty unimpressive. The mercury-loaded bullets did about the same amount of damage as regular hollowpoint .22’s. They punched .22-size holes going in and holes about as big as a penny going out. We were pretty disappointed. I’m not willing, based on one half-assed experiment conducted on a melon, to say such cartridges wouldn’t be more destructive to a human shot through the head than a conventional cartridge, but my gut feeling is that they wouldn’t.
Regarding those mercury-filled bullets, two points:
1.) I’ve always wiondered, given Forsyth’s explanation, why the bullet didn’t tear itself apart when it was fired – you have the same inertial force trying to get that stationary blob of mercury moving in the first place.
2.) In the movie The Exterminator they show a guy making explosive bullets by putting mercury into drilled-out bullets. But the guy is working with a propane torch over bullets still in their shells, which strikes me as phenomenally stupid.
I’d vote for BHD as the least down time of any action movie I’ve ever seen. We Were Soldiers comes in second, and would tie were it not for the in-training scenes in the middle.