A BOB must be light enough that you can carry it readily and not affect your agility too badly.
No one is served if you twist an ankle when jumping over a highway divider with an heavy load.
My BOB plus gun/ammo weighs less than 30 lbs (and I weigh 230 lbs and ruck march regularly) so its light burden for me and thats on purpose.
Less is more.. dont let a BOB fatigue you..
A gun,ammo,water, first aid kit, compass, a map, spare socks, spare underwear, spare t shirts (use tan or dark ones.. in a pinch you can wear t shirts as a extra layer on your head when its cold), lifestraw,a woobie, a light rainjacket, toothpaste/toothbrush, couple of protein bars. Done.
What do I not carry?
Excessive Ammo load..
Excessive water load
Sleeping bag
Extra boots.. the ones I wear must be good enough
Extra Firearm.
firemaking flint
Tomahawk...
Tent