I liked the episode, there was plenty of tension
The MacGyver contraption was stretching it a bit- the Nazi guy could have easily smacked Walt in the head as he tried to park the car in the right position. Seeing they were going to kill him anyway.
There are many gun enthusiasts on the forum- is that sort of thing plausible?
240?
The thing is, such a contraption is NOTHING you'd expect.
So there would be no doubt at all, it wouldn't matter WHERE Walt would park, they'd kill him either way.
Smacking him in the head would be totally unnecessary.
Sure, they were going to kill him, but not outside, they still had a certain degree of respect for the genius, you don't smack someone like Heisenberg.
Also, smacking someone so early would give that person ideas, i'm sure they had a certain degree of curiosity and wanted to hear what he had to say first.