This may not be much help right now, but it might be at a later date--besides using a small flashlight to look in the case---if you have a digital scale--weigh the case before you drop the powder and zero the scale with the case on it. Then re-weigh with powder and the scale will give you your exact charge weight. If you really trust your powder measure, you need not do this for every case, but maybe 1 in 10. But if you get a big difference at case # 50, you would be wise to go back and check # 41 through 49.
The entire point is moot if you use a slower powder like HS-6 or N-340 and such. Also the chances of double charging a case are reduced if not eliminated by using a slower powder that fills the case better, to say nothing about better performance.
I like Hodgon's Lil Gun for all my magnum pistol loads--partly for the way it fills up the case and partly because I get good accuracy and power with it.
A slower powder can result in an increase in perceived recoil, which in the .38 special is not really a problem, but the .357 mag can be a bit much for some more sensitive--maybe poetic--folks when using a slow powder..........
"If the enemy is in range, so are you." - Infantry Journal