Simply stated, the angle of entry for a bowling ball traveling down the lane is the direction the ball travels when going into the 1-3 pocket from the break point for right handed bowlers and the 1-2 pocket for left handed bowlers.
The USBC (United States Bowling Congress - the governing body for the rules and regulations for the sport of bowling) has publicized that a pocket strike occurs at board 17 to 18 with an entry angle of 4 to 6 degrees.
A very strong or steep angle of entry, perhaps a 6 degree angle of entry or greater, risks reducing optimum pin carry. A weaker angle of entry also produces reduced pin carry, perhaps a 4 degree angle of entry. Equating pin carry to angle of entry is not a precise science and varies from bowler to bowler.
For the best energy transfer, a ball needs to be rolling into the pocket, not merely hooking into it.
The three phases of bowling ball motion are the skid phase in the front end, the hook phase in the mid-lane, and the roll phase on the back-end of the lane.
Between 4 and 6 degrees angle of entry will be ideal for optimum pin carry on a given night, on a given lane condition. A 5 degree angle of entry might just be the perfect angle of entry on most house conditions to gain optimum pin carry.
How does this equate to your delivery technique?
“Power players” who hook the ball the most because of their strong rev-rate and relatively high axis tilt will achieve about a 6 degree angle of entry into the pocket and will likely produce very good pin carry but run the risk of leaving frequent back row pins on solid pocket hits such as the 7 and 10 pins or 8 and 9 pins.
“Tweener players” achieve about a 5 degree angle of entry and the pin carry is certainly very good with the nearest to optimum levels of carry as any angle of entry yields.
“Stroker players” will achieve about a 4 degree angle of entry and will also get good pin carry but perhaps not the maximum carry potential as a player with a higher rev-rate and a greater measure of axis tilt.
With 4 to 5 degree entry angles you generally only worry about corner pins or a 4 pin (6 pin for left handed bowlers) if the ball contacts the pocket a little high.
Angles of entry at 6 degrees or higher run a risk of leaving any of the back row pins as well as the occasional big split. These leaves occur more frequently with big hook angles of entry as opposed to the more modest angles of entry.
In the final examination of angle of entry, the lane conditions coupled with the bowler’s delivery technique are going to determine what the best entry angle is at any moment.
You can slightly alter your entry angle by altering your delivery technique but not so much as to lose accuracy. Increasing axis tilt and rev-rate might help you achieve a bit more entry angle and pin carry correspondingly but that is something to be determined by you and/or your coach.
Altering the drilling layout and changing ball coverstock surface textures will also influence entry angle slightly. However, the chief concern here is making sure you get the most consistent ball reaction and hit the pocket at the highest degree of efficiency as possible. You shouldn't only be concerned with pin carry.
