Your benching form is probally the reason why you are not getting the chest gains you want. Your probally "trying" to train your chest, but end up training you front delts and triceps due to your form.
Here is proper benching form on how to increase stress on the pectorials and limit front deltoid and tricep involvement.
- Drop your traps and shoulders down
- Pinch your shoulder blades together
- Puff your chest up
- Drop elbows down slightly under the nipple.
(by having your elbows up high at 90 degrees like how most people bench you will notice much less stress is being applyed to the chest and the front deltoids are being worked much more. Also lowering your elbows will increase your bench, just take a look at how the power lifters bench all with there elbows low, the higher your elbows the more front deltiod involvement, the lower your elbows the more chest involvement)
- Dont lock out or roll the shoulders.
(if you follow the steps above you shouldent be able to roll your shoulders anyway, but its always best to stop short just before lock out. Why? When locking out the stress is removed from the pectorials and placed on the elbow joints, also the top ROM of the bench press is more triceps and front deltoids, thats why when you see pros benching like Ronnie Coleman you notice he dosent lock out his elbows)
- If using dumbells slightly rotate your thumbs upwards
(put your hands out infront of you and turn up your thumbs just a little, this is the angle you want to hold the dumbells at, so that even less deltoid is being involved, this is why i prefer DB over BB)
Follow these steps and it will hit your chest.
Also watch this video by Charles Glass, he explains quite good on how to have maximum stress on the chest and limit your front delt and tricep involvement.
http://www.bodybuilding.com/fun/glasscut3.htm