Ok.Great for the input.
so 315,000 bricks divided by 15 wagons is 21,000 per wagon.
You stated 6750-7250 per wagon. So average 7000 x 3 flats per wagon is 21,000 so that works out.
Average brick pack is 400 bricks so 21,000 divide 400 is 52.5 packs. So my guestimate of 18 packs by 3 is about right then.
Not sure how im going to emulate 54 packs per wagon over 10 wagons!! But model railway always like projects in duplicate!
Does anybody sell packs of bricks?