Whether I'm out for a couple of nights or a couple of weeks I usually use a 100 litre PLCE Bergan which I fill to the top with 'just in case' items, extra clothing, wet food, etc. Of course I am always carrying too much weight and it can be a nightmare traveling any distance.
I've been thinking recently of downsizing to a Pro Force Trooper 65 litre 'sack (fits my 6' 4" body better than my long back Bergan) to try and cut down on the amount I carry, but after reading through this thread and some others on BCUK I've changed my mind.
Today I decided to get out my 20 litre daysack and try and pack it with bits for a three-nighter. Amazingly I've got everything in!
So I'm off out tonight with only the following:
3mx3m Tarp
Bivi bag
Sleeping bag (well compressed!)
Sleeping bag liner (often used as scarf/head covering)
Hammock
Tree huggers
Assorted Paracord
Dog food tin hobo stove
Folding saw
Knife
Ferro rod
Crusader cup & lid
2x Boil in the bag flavoured rice
Teabags, coffee, tobacco, lighter, mobile, book, sunglasses.
Dried birch polypore (false tinder fungus) from a previous bimble (discovered today that it catches a spark beautifully)
Sleeping mat (strapped outside)
Total packed weight is about 5kg.
I have a little bit of space left to fit in a few more 'boil-in-the-bags', water bottle and alcohol stove if I really was off for a few days and I could easily create more space by removing the hammock & huggers (but I do like to hammock where possible).
Tent pegs, bivi poles & spoon I'll make as required. Tinder I'll collect whilst walking and keep in a pocket to dry out.
I'm now thinking of buying a 40-45 litre 'sack for all excursions during spring/summer allowing me to have all of the above plus waterproofs, spare clothing and beer!
All of you using large 'sacks should grab a small bag and try and pack it with only the essential items and see for yourselves how small a space you really need.