I use my .30 cal can on my .223 and it works great and is super light. Silencerco Scythe TI. I imagine you could get a little better performance from a dedicated 556 can, but I like the diversity.
I was given a benchmade altitude a couple years ago and I love how light it is for backcountry hunting, but it isn’t the most comfortable knife to use for very long time periods. I may try wrapping the handle in paracord or something to try to make it more comfortable.
I recently had a lower back injury and went to a physical therapist. They emphasized core strengthening and stretching. Learned some great techniques. I’d recommend professional help for a bit just to learn some techniques you can do on your own going forward.