I have to chime in with shwrdr and deputy125, you're flirting with danger. First, buy a scale. Even a cheapie is way better than dippers. You will find dippers aren't very accurate and don't drop exactly what the Lee charts indicate.
Trail boss is indeed designed for high load density but don't let that fool you. It's burn rate (grain for grain) is nearly identical to Bullseye, which is one of the fastest powders on the market. You can easily over charge a 45 Colt case. IMR charts show a max charge of 5.8 gr for a 250 gr LRNFT bullet at 12,700 psi. Considering 14,000 psi is the max pressure for a 45 Colt, an extra .2 grains will no doubt increase pressure even more. Besides, with dippers and a slightly heavier bullet, you don't have a clue what the chamber pressure will be.