Just an fyi - a simple and affective method of slinging the rifle to your pack.
I cut the top bar on my pack leaving about a 1" stub. This keeps the rifle from slipping off the pack. Then I replaced the pack pin with a 1/4" X 2 1/2 phillips head bolt, washer, and lock nut. I bent the bolt upwards to hold the sling. I then wrapped the bolt with elec. tap to reduce abrasion on the sling. The purpose of the bolt is to keep the weight of the rifle off of the pack bag so it won't eventually tear at the grommet.
Be safe out there and keep your rifle handy - bear maulings seem to occur on a regular basis these days.