I use a gunslinger back pack, it has worked out well after some changes. with the long guns the pack seemed to short and was top heavy so I had a shoe maker add 8" to the bottom pocket! it was too much and the barrel hit my leg when I was walking so back to the shoe maker for a trim. I ended up with about a 4" addition to the bottom and made a big difference. next I had him sew a handle on the right side so when taking the pack on/off it always but my gun rightside up and the zipper side on top also to get to my range finder etc., then I ended up robbing the straps off the top cover and tying them to the hook loop. I run the straps thru the thumbhole in my stock and snap them shut to keep the gun from flopping side to side. I don't us the top cover.
It ended up being very nice and easy to carry and have room for most everything you need for a day outdoors.
I have used it several times and I'm very happy with it and the owner of the company " Glen" is top notch to deal with.
I tryed all kinds or slings and brainstorms but putting it on my back and hiking to my vantage spot works for me. Also take a friend and let them have the close shots and you will be set for long range.