I use this tool bag I pick up from my local Army-Navy store. They're about 22 bucks. when they wear out, I pick up another. They last a long time!
I can tote:
2 handguns in their cases (one in a holster)
12 mags in the side pocket. 4 or 5 more inside.
800-1000 rounds of ammo, depending on how they're boxed.
1 staple gun for putting up targets (in the other side pocket)
2 mag loaders
1 can of copenhagen
Sometimes I carry my ammo in an empty bucket, which comes back full of brass. If I carry ammo in the bucket, I can put two sets of hearing protection in the bag, otherwise I hang the muffs on the handles. I take every precautionary measure possible to keep from looking unprepared when I hit the range