id personally want more, expecially if i was to pack out meat as well. For me 4000 CI is cutting it pretty close for 5 days, even with good gear. I also dont like having anything outside the pack though.
I once did 8 days out of a Blue widow (around 4500) and never again would i try that or even a few days less. Too much stuff flopping around on the outside of my pack.
Now take a 4000ci kifaru pack and you have a different beast, you have the ability to add a pod, or some pockets to the outside so if you had to haul meat and gear, you could easily expand your space.
I always smile at this question because it is so dependent on what the persons gear is. Someone with ultralight gear could fill half of a 4000 ci pack while someone else might not be able to fit all of their not so new stuff into it. My suggestion when looking at what size pack to get is to lay all of your gear out in a rectangular cube and then measure its dimensions to see how may ci you will need. Then, start looking for a pack that will have at least that much space or better still half again as much to allow for wasted space when you have to pack fast and cram everything in there.
As for how much space the meat will take up, try seeing how many ci's you have in 5 pounds of ground beef and then multiply that to get an idea of how much space your boned out deer will take up. Also, if you plan to try and take your meat and your camp out in one trip then give some thought to taking a bag (maybe a contractor grade trash bag or trash compactor bag) with you that you can put your camp gear in and then strap to the outside of your pack while you keep the meat inside of the pack body.
You should be able to do a 5 day hunt with that type of space but I would want more for the pack out. Do you have newer lighter gear? I also agree with Lawnboi, that if you have a Kifaru you can add to it and not have the feeling of everything flopping around, because of how things attach onto it. What pack are you looking at, or do you have one already?
I had a blue widow and didn't have an issue getting 7days of gear in it, i did strap my zlite to the pack. Really you should be able yo do 5 days out of this, just might have to strap something on the outside but only you will know if that bothers you.
Like whats sorta already been stated. What amount of space does your gear take up?
A boned out buck is going to be around 65ish pounds of meat plus the head. In my opinion and experience that's a load it's self for me. My guess is that's going to pretty much fill your 4K bag your talking about. Most.....I say most 4K bags that's about max on weight anyway.
A lot depends on the design of the pack... The Eberlestock X2 is listed at 2000 cu/in but can carry way more due to the batwing design.... same with the BL2200 and the older BL2800... I've bivied for 5 days out of each one of these... My buddy did 7-days with his Blue Widow and had great luck with it (didn't have to strap anything to the outside)... He's gone to an X2 as well because it is smaller...
As a general rule, whatever size pack you have, you will likely fill it up so go with the smallest you can...
I would say simply, no way. Even with the best, lightest, smallest gear, food and a boned out buck, not going to happen. If you strap a lot of gear to the outside in dry bags, it could be done. But with todays pack choices why would you want to.
My gear takes up about 3000-3500 depending on how much food if it is not a late season hunt where my clothing system is changed. I have all lightweight, small and unfortunately $$$ gear. A boned out mule deer I think would take up every bit of 2500 and that may be under estimating.
Go big or go home. I'm using 6500 CI's for a 10 day bivy trip... But I'll have it split into 2 5 day trips from the truck. I'll have enough space for my gear and a load of meat +cape/antlers on my first trip out. Hopefully bringing out a bull elk in 2 trips. Go big and cinch it down. You won't be sorry.