I want to switch from chin ups to neutral grip pull ups. I tried doing a couple today just to test out how it feels.

Near the top of the pull up, I felt like I was doing more of a hammer curl than a pull up. I couldn't get my elbows to go behind mee. Any tips? I feel like I'm doing it wrong, but I did get a pump in my lats. It'll probably still work my back, but I might not get the full benefit.

Have you seen any how to videos ? It is a bit hard to guide you as I cannot see how you actually do the exercise. Pull ups is indeed a great bicep exercise, and when you do a wide grip you work your lats ALOT. However your biceps are getting a good amount of deep muscle fiber work that increases the peak, so no matter how you do a pull up your arms will still have work to do !
It is said that one needs around 200-300 reps of an exercise to master it, wheter this is true or not the point is that you need more practise

Grip position, grip width, and palm position all affect how the pull-up or chin-up will stress the back and arms. Chin-ups with palms facing towards you put equal stress on upper back and biceps when you keep the arms at shoulder width. If you bring the arms closer together, more of the outer bicep takes the stress while hands further out stress the rhomboids, traps, and rotator cuff supporting back muscles (teres group, infraspinatus). Pull-ups, with palms facing away from you put more stress on the lats and upper back than the biceps. Closer hand placement gives you thickness while wider hand placement emphasizes width. Neutral grip tends to focus more on back thickness than width since the hands are closer together. The brachoradialis muscle takes more stress than the biceps as well hence the feeling of being like a hammer curl.

You need to experiment with the different types (chin-ups vs pull-ups) and hand positions (close and wide) to see which hits the desired muscles. Variety is the key to growth. I like doing chin-ups because they hit the back and at the same time hit biceps (especially since I need to re-build my left bicep after my injury). I usually super-set them with some sort of wide grip back row (bent over, T-bar machine, etc). When I want to focus on back width (which fortunately I have been blessed with already), nothing beats wide grip pull-ups.

John