Many people play sandlot baseball or softball. Pick-up games are common in some communities. These informal games allow for the use of "juiced" bats. Juicing refers to the process of tampering with the bat to make it more effective. The ball comes off the bat faster, making it go farther while endangering the physical well-being of the defenders. Most leagues have rules governing the use of juiced bats so, before juicing your own bat, refer to the rules of your league. Weigh the pros and cons of using juiced bats.
Shaving a Metal Bat
Pop the end cap off the end of your metal bat. These caps are not designed to pop off so you need to use a pry tool such as a paint scraper or flat-head screwdriver.
Shave the inside walls of the bat with a metal file or lathe. Do not scrape more than a millimeter out of the barrel. You are looking to increase the trampoline effect of the barrel, not make it brittle to break.
Pop the cap back onto the top of the bat. You may need to use force or shave down the rim of the cap. Use crazy glue to seal the cap shut for added security.
Rolling
Heat your metal bat up. Leave it in the sun for the afternoon or leave it in a hot car.
Place the bat on a surface that can withstand hammer hits such as collapsed cardboard boxes or pile of towels.
Hit all sides of the barrel of the bat several times with a rubber mallet to thin the walls of the bat, much like shaving but with less chance of getting caught. This will age the bat prematurely, but it will have a juicing effect.
End-Loading
Pop the top of the metal bat off as described in Section 1.
Crazy glue several small metal weights to the inside of the barrel. You can use magnets to weight the end of the bat and the magnetism will help hold them in place. The closer to the end of the bat the better.
Replace the top of the bat as described in Section 1.
Swing the bat with extra force due to the added ounces at the end of the bat. This increases power and is referred to as "end loading."
Warnings
Juicing your bats is highly unethical and it increases the chances that the bat will break. A broken aluminum or composite bat is a hazard to yourself and the players around you.