I actually had slots put in like Mag-Na-Port. 2 on each side but they were cut larger on the inside and tapered to the outside. Worked on the principle of a garden hose and a nozzle. As you start to shut off a nozzle the stream get stronger and shoots water further out and if you open the nozzle all the way the water has no force behind it. So the gunsmith who did this for me used the same principle on the slots. The larger hole on the inside and got smaller as they came to the outside. Worked great but traded the barrel when I had Pinnacle Custom make me a barrel with an integrated comp and port holes.