Not just so he can borrow the murder weapon to obtain the spent shell casing. But also the symbolism of him having to shoot a cop. Even though at the end he ends up having to kill all 4 cops without his gun.
I have always thought it was partly to get Davis to let him shoot his gun, and partly to send a bit of a message - "A cop in a place where he isn't supposed to be can get shot by accident, even by another cop." His look back was check Davis' reaction - "Did you see that? Did you see what I did? It happens." Of course, it wasn't until he showed Briggs the bullet that Briggs and the others realized he was going to come at it from the 'wrong' direction and that he *didn't* approve of their methods.
Harry, purposely, threw the competition, so he could, ultimately, create an excuse to fire Davis's gun, shoot a bullet into one of the range combat props, retrieve the bullet after the competition, and see if it matched the bullets used on the gunned down hoodlums.
Just watched the film again last night, and that particular scene always struck me a different way. Harry was having suspicions that it might be a cop (Charlie McCoy) or cops (the rookies) doing the killings. During the "combat" shoot-off, a cop target comes upo, and Harry shoots it. Unintentionally? I think so, he seemed a bit shaken, if only for a moment. Harry doesn't want to believe what he suspects... but after checking the ballistics on Davis' bullet, he tells Early, "I just saw something that made me lose my appetite." His partner probably wondered what that could be, since earlier in the film, looking at a multiple-gunshot victim, blood and guts all over the place, upset Early, but not Harry. "How can you be hungry after looking at that?" "Looking at what?"
He loses on purpose. One reason is to create a pretense to use the other cop's gun, the other as a plot device to foreshadow Harry killing the other cops later. The faint comment from the peanut gallery "he shot one of the good guys" is perfect.
No doubt he did it on purpose. You can even see the look in his face when we hear the comment "that was a good guy", he giving a look that says "are you sure?".
Harry wasn't Superman; he just *might* have lost to someone we've already been shown to be a young, practiced, highly-trained shooter. And he didn't need to lose to have an excuse to try Davis' gun; win or lose, he might very well have asked to try it, either way.
One amusing thing about that "combat" course: Why on earth did they fire multiple shots at targets they successfully hit with the first shot, and what was the point of the dramatic diving rolls on the ground just before shooting? It's not like either move would have gotten them bonus points.
Harry wasn't Superman; he just *might* have lost to someone we've already been shown to be a young, practiced, highly-trained shooter
I agree but I'll go further: Harry lost the competition because Davis was better (that day) which I believe was the point. Davis beating Harry showed that Harry was was going up against men as dangerous with a gun as he was. We always knew he was better than the kidnapper/rapist/murder in the first film, or any bank robber, but these guys were expert marksmen. It made the aircraft carrier scene more dramatic.
But remember that other than the one wayward shot which cost him the match, Harry was faster than Davis in the combat test so the rest of us could take solace in that much at least.
I think Harry's loss served dramatic purposes, too many for the loss to be purposeful.
As a plot device, it foreshadowed him killing cops. His reaction was also, perhaps, his realization that he might have to kill cops. It also demonstrated that Harry's not perfect, and that these rookies might actually pose a real threat to him. Davis is the last to die, after all.
He could've borrowed Davis's gun regardless. He didn't have to lose to do that.
I most definitely DISAGREE that he shot the cop-target on purpose as a message to the rookies. For one thing, he still wasn't sure it was them and, more importantly, he wouldn't want to them to know he even suspected them.
I've always thought that he was just off his focus because of what was going on, and that's why he shot the innocent target. He misses on purpose when he asks to try Davis' gun, but I always thought he gave it his all for the competition.