Consider bringing an extra water bottle (Nalgene HDPE bottles are light and sturdy)/hydration bladder if you have room in your ruck. Keeping water in means it also keeps water out, so you can pack stuff into the bottle and it'll stay dry (extra pair of socks, a small snack), which keeps the bottle from being wasted space. And if your hydration bladder fails and you have no backup option, you are Fucked with a capital F. Don't be Fucked with a capital F.
Listen to /u/jamesvreeland. You don't pass Selection and a billion events without knowing your shit.
Don't bring a North Face/Jansport bag to an event, particularly not a Challenge. I'm not saying it won't survive, but if it doesn't, it's a nightmare scenario. Not saying it will happen (I've seen those bags survive events), but you wanna minimize the risk. Go to a surplus store like James and /u/perryw said and get an ILBE, or consider a 5.11 Rush 12. They're tough enough to survive an event.
I've got the 511 RUSH12 and it's worked great for me.
If you dont mind the 'tactical' look, take a look at MOLLE options. They are like Lego for bags.
Yeah, I've never had one go more than 2 year. At least up until I looked up reddit threads for good backpacks and finally began walking the righteous path.
You can get a red GR1 for $200 at http://www.goruck.com/steals-deals/c/99
alternatively, while looking for a cheaper bag I also looked at and bought the 5.11 rush 12 at about $80 at the time, and I'm happy with it and it seems well-built even if it's less popular with the bifl crew here.
I use a 5.11 Rush 12 backpack for handguns, PPE, a few tools, and sometimes ammo if I'm only bringing a couple of handguns. I use this pack for travel a lot, as well.
I'll use a Plano ammo can when I'm bringing along more ammo, especially for rifle ammo and heavier pistol ammo like .45 ACP.
Rifles go in Midway tactical rifle cases.
Looks like Rush backpacks
http://www.amazon.com/5-11-Tactical-Rush-Back-Pack/dp/B005AG3A9C