Shooting off a ruck...

[Knowledge]

Another option: get a bag with MOLLE on the back and attach a rest. You’ll look like a humpback, but it’s pretty well the ideal.
Attachment 62618

Yeah, I've used a pair of binoculars standing them up as a field expedient rest to take a few things. Might want to use covers so the lens doesn't scratch.

[Brent Yamamoto]

Another option: get a bag with MOLLE on the back and attach a rest. You’ll look like a humpback, but it’s pretty well the ideal.
Attachment 62618

I have one of these, though I haven't used it so much.

I do think it's a useful piece of kit, but it still really depends on what you have in the pack. Also, as we've discussed, the molle packs are relatively heavy, and when this is attached you're locked into shooting with the pack parallel with the muzzle, rather than perpendicular. Sometimes that's no issue, sometimes it is. This would still be useful if it wasn't attached to the outside of the pack, but I'd need to test this more to see how well it actually works.

The rest isn't very heavy, but neither are bipods or even some of the small tripods. And they offer some more flexibility. I have a great miniature tripod with a small rest (I'll have to post a pic another time, don't have it handy) that is very useful and more adaptable for different options.

Magpul even offers (at least they used to) an MLOK tripod attachment that works with regular camera tripod mounts. Very useful and a bit more flexible than bipods.

Lots of different options that all have value.

[45Smashemflat]

As Yondering said, in this application, your pack needs to behave like a big sand bag rest. Pack it accordingly. I use a Kifaru Hooligan with a couple of external pouches as my go bag. It works well as an expedient rest.

[Jons999]

I have an Eberlstock M5 pack. It’s designed for hunting and is just about the right size for 3 days. I actually took it on a 10 day back country hunt and it was stuffed full with tons of crap strapped to the outside. Has a built in rifle scabbard in the center of the back and you can pull the rifle out with the pack still on. Also has lots of attachment points for external pouches, also has built in pouch for water bladder. Carries up to about 80 pounds or so without being too rough on the shoulders once you have it properly adjusted. There are some lighter/tougher packs out there, but imo this pack is a good value for $400 bucks. I did practice some 300-400 yard shots off the pack and was happy with it but I don’t have experience shooting off any other packs.

[45Smashemflat]

I have the RMEF Team Elk from Eberlestock as well. I think that’s just an M5 with some “bling.” It is a great pack. You can certainly load it with more than you want to carry. Sometimes you just need old school frames.