Or at least I think this is the case. Unfortunately the rigour of the movie might be its downfall - it makes no concessions to the audience to make the story easy to follow. When we see one of the characters in a scene it's not easy to tell which of the scenes, either earlier or later in the movie, are in that characters history at that time. And of course by time a potential candidate to be in his history does appear later in the film, we no longer remember the details of the earlier scene. Memento was a straightforward film shown in reverse. (And also inconsistent, as if reversing the story was too much for the scriptwriter to handle.) Primer forks, loops and twists like no movie I've ever seen. As a topological space it has a high genus.
Unfortunately, it was too much of a challenge for me. I really have no idea what happened, although there appears to be an interesting sequence where one of the characters repeatedly travels back in time, each time making slight modifications to his actions, in an attempt to iteratively optimise an outcome. But what that outcome was, and why he tried to achieve it, is beyond me. I guess I'll have to watch it a few more times. It's very rare that a movie has provided as much of an intellectual challenge.
And one point in its favour - not only was the technobabble not excruciatingly bad, it was even believable in places. Primer is one of the few truly Science Fiction movies I have seen.