Contour Enthusiasts Group Archives Forums General Common Interests Any Gamblers here familiar with doubling your bet?

A friend and I figured out the doubling your bet theory for blackjack and went to a casino the other day to try it out. We had tried it out at home by dealing out 1000 hands and saw that you lose 6 times in a row once in 500 hands. We won some good money, I won 155 and he won 350. Is doubling your bet illegal? I have heard it is but they never said one word at the casino and we both played at the same table. Just wondering what others thoughts are on doubling your bet.