Having forward shaft lean at Impact for your irons allow your hands to stay ahead of the club head at impact. This allows the club to be moving down as it enters the hitting area. The result is that the ball is struck higher on the face. This allows for the player to strike the ball around the fifth score line up on the club face. This is where the clubs sweet spot is. All irons are designed to have forward shaft lean at impact.
Here is a photo of Tiger Woods with a iron at impact we can see the forward shaft lean and the compression on the ball. We can also see that the center of the ball is on the center of the club face. The club still has not reached the bottom of the swing arc. That will happen four inches ahead of the center of the ball. Now the ball will roll up the face of the club as have backspin. The backspin helps keep the ball in the air longer and also gives it greater stopping power when it lands. This is why we see balls check up and stop within a few feet of where they land.
So how can you get this to happen in your swing? The best way is to change your thought process and try to Swing through the ball to the turf in front of the ball taking a divot. We always want to take a divot with our irons on a full swing. The other is to start the downswing with a slight lateral move of the hips and a turn as if you where throwing a ball. Most amateur players start down with their arms and shoulders. That leads to inconsistency in where the bottom of the swing arc happens. It can lead to fat and thin shots. If we use our core to deliver the club rather then our hands we can then move the Swing bottom forward and produce forward shaft lean at impact.
There are drills that you can do to help this happen. The other is a hinge and hold drill. The best drills usually are without a ball involved. That allows you to feel the motion and not be so focused on the results of where the ball ends up.
Here is another drill using a alignment stick and no ball to feel what the body and arms do coming into impact.
If you would like to take a lesson contact Impact Zone Golf in Naples at 239-236-5548 and ask to schedule you lesson with Bernard Sheridan.