I used to do heavey barbell movements for biceps they built bulk but my biceps "peaks" really did not come out untill I started do "supination dumbell curls"
starting in a hammer position and twisting the hand up and pinky above the thumb then squeezing the biceps and lowering back to start
Also doing arnold style concentration curls leaning over one hand on my knee then other grabbing the dumbell twisting the hand as I raise the dumbell bringing the weight up to my chest and face area then slowly letting the weight down.
The best way to get the biceps full range of motion is through dumbells curls rather then barbell.
the inner head of the bicep attaches to the forarm in such a way you have to supinate the palm of the hand to fully contract the bicep to reach full contraction allows you to build a fully developed bicep.
stand in a normal position with hands to your side use no weight, keep the elbow down and slowly raise the forarm (keeing elbow at your side) untill it is in front of your body. ( like you have your hand out for someone to put something in it (more of a 90degree angle)Now play with your "supination"
.turn the pinky up and down a few times you will see your inner head contract and relax as you move the hand back to normal with out even really using your bicep ,then turn your palms up and down over and over and watch the bicep inner head ball up.
it will contract on its own as you turn the pinking higher then your thumb.
do it a few times and you will see how greatly this effects the full contraction of the biceps
so grab the weight plams neutral at your side then as you raise the dumbell turnthe palms up, then go beyond it and turn the pinky up further then the thumb.
That was arnold "secret" he wrote it in a book over 30 years ago that bodybuilders were not supinating the palms to get full contraction and squeezing the inner head at the top with the pink higher then the thumb.
Not saying you will have arms like arnold but anything helps
this is a quick example watch around 30seconds into it
http://www.youtube.com/watch?v=HryZtZZvYh8
see arnold bicep he is bent over and raising the forarm with the pinky slighty higher not much and he is contracting the inner head of the bicep
squeezing the inner head,
here arnold bring it to his face
http://www.youtube.com/watch?v=Rg0dJVj8ADE
arnold did tons of variations of supination curls
is it not a fact he had the best biceps in the sport ?