Kadoba is right, this is not how hardware-accelerated games are supposed to be designed. You're effectively loading small videos in to a limited VRAM resource. It's much better to have a bunch of single-framed sprites which you move around, scale and angle, with effects, to create explosions. That way is actually smoother (not frame by frame, rendered on the fly), timescales (you can move explosions slowly and smoothly, whereas frames would just go past slower like a slideshow), uses far less VRAM, and is visually more interesting since you can add randomness.
If you do need frame-by-frame animations, try to keep them small in dimensions and as short as possible. You could also try downscaling them all to half size, then stretching them up - you might not see the difference, and save up to 75% of the VRAM.