Didn't know there was a standard length, lol. The actual size, make and model might be helpful to size one correctly.
Also, are you wanting budget or luxury? Space for 1 or 2?
I have 1 of those and it is very sturdy.Thanks, everyone. I ended up with four of these: Amazon.com: BLACKHAWK Sport Tact Carbine Gun Case, 36-Inch: Sports & Outdoors