I've been bowling this year.  I've bowled a few 700 series at the beginning of the year, but now I have a lot of trouble carrying during the game.  I've changed my aoa, ball, and speed.  I have a ball spinner so my balls are well taken care of.   Balls:  Ebonite Cell (Dull), Black Ice(polished), and RotoGrip Element(polished).  I leave the 8pin, 9pin first, then once i adjust i start leaving the 10pin.  I'm thinking of getting another ball. Give me some advice.
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Bowling is not only skill but a little luck helps

And you adjust leaving an 8 pin? Okay.. And the 9 pin? Could be a little high, but adjusting off of an 8 pin is a pretty dumb move.
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http://www.kennyskidmorebowling.com
Stand left, throw it right, and strap it like a trojan!!

I was having this same issue for most of the year.  I was leaving a ton of 7 and 10 pins.  I worked with a couple of coaches and discovered I was throwing the ball too hard.  This was caused by the extremely dry shot the place had put in early in the year.  I needed to reduce the speed by about 1 or 2 MPH to allow the ball to get into a full roll at the pins. What we saw was that the ball was sling into the pocket instead of rolling in.  Since I have made this correction, by lowering the starting position of the ball and lowering my backswing, I have shot 5 700 sets in a row.  It made a real difference in my carry.

Leaving an 8 pin for a righty is a true tap.  There is no reason to adjust for that.  It just means you got unlucky.

If you're leaving the 9 pin, move a half a board with your feet left.  That just means your ball is driving too hard off the spot and coming in at an extremely high angle.

If you're leaving 10 pins, move a half a board to your right with your feet.  

If you're still having issues carrying, it is probably something else.  Make sure you're getting out of the ball clean.  Getting a mitt full of the ball is a great way to not carry.
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Ahhh Disco Biscuits!