I strap a VISM NCStar tactical shotgun scabbard to the right side of pack...attach a half inch soft woven tubular climbing webbing starting with a ~30-36" length with a loose loop around the pistol grip. Other end looped to easily accept gloved hand and extends 5 to 6 inches past buttstock end. Total length 16". Easy to grasp loop end, lift straight up and 18" lever actions or police-type shotgun equivalents quickly and smoothly can be handled to firing position.
Protects wood stocks and blued finishes, allows hands to be free when scrambling or using poles, etc. Barrel pointing down and away from body or companions when overcoming obstacles.
Obvious shortcoming is drawing when in heavy brush low hanging branches overhead.