Yes, it is possible. T-Max 100 demands consistent technique from initial exposure all the way through the wash cycle. How can you be sure the second test was overdeveloped and not overexposed? Did you shoot the same scene, with the same lighting, and the same exposure? If not, you have too many variables to know what is causing the problem.(posted 9166 days ago)Take heart, you can nail your T-Max expsoure/processing procedure without resorting to studio lights and a densitometer. Shoot three 12-exposure rolls of a gray card under controlled conditions. Make sure you meter carefully, bracket your exposures by one-half stop, and record all your exposures.
Process one roll at 6.5 minutes, one roll at 5.5 minutes and one roll at 4.5 minutes. Print contact sheets of each. One roll should have an exposure where the gray matches card at your camera's recommended exposure when the film base disappears on the contact sheet, assuming your light meter is working correctly. You now have a development time that will yield your expected results.
Make sure you monitor the temperature very carefully while processing. You might want to invest in a tempering box. At the very least, use a tempered water bath. You can build one with nothing more than a small plastic tub, a thermometer, and an aquarium heater.
You might also want to order some BW-2 developer from Photographer's Formulary. I get better results with it than with T-Max developer, but other people I respect get excellent results with T-Max, and some prefer D-76. You can find Photographer's Formulary at http://www.montana.com/formulary/Index.html.
Experiment a little, and don't be afraid to make mistakes.