Don't give up on the adjustable bar. I would not load without one. Something happened, and you need to find out what it was because it may happen with the MEC bars too. Pellets in the powder tells me that one or both of the necks on the bottles are worn out or were not screwed down snugly. To be throwing nearly double charges something is drastically wrong, mark the setting on the charge bar with a grease pencil and load a few, see if it is moving. You may been to tighten up the friction screw to keep it from moving.
GET A BAFFLE for the powder!!!!!!!! Get one NOW!!!. I have never had the powder charge move once I put one in. When you fill the powder bottle tap it on the sides and top to settle the powder out, when it stops moving you can stop tapping. The motion of the press will pack the powder in the bottle if you don't do it beforehand and the charge weight thrown will increase.
You have also learned a VERY important lesson, sample the loads for powder charge every once in a while. I load on a progressive, so I load large quantities at a time. Even when I am craking out a run of 1000 shells or more I sample one shell about every 25 loads. Pull it out of the press and weight the charge, your scale will already be set for the weight so if the beam floats all is good. Takes less than 10 seconds.
You very likely could have shot them and not blown up yourself or your shotgun, but it is MUCH safer to catch them before. Double charges happen once in a while on some presses if the operator is not paying attention, I have seen a few of these shot at the range, pop pop BOOM type of thing. Scary to be standing next to the guy.