Ok, so I decided to try out a spectre CQB sling on one of my mossberg 500s. So I put it on, and go shooting clays today. Out of 50 I get 2 light strikes on the shells, and thought at first maybe they were hard primers, etc. so once we're finished, I was still thinking wth was going on, since this particular mossberg has seen 500+ shells with no issues at all.
After discussing it a little further, I bring out my other mossberg 500 with no sling, pop in the 2 dented primer'd shells and this mossberg fires them no problem at all. So I was thinking, that's strange. After thinking what may be causing this, I remember I installed the sling between the barrel lug and the tubular magazine, possibly creating more of a space between the two than there should be, leading to some light strikes.
Does this sound right? Also seems like the barrel came a little loose on the one with the spectre sling (because I believe I installed this incorrectly). Basically, I know I'm an idiot, and I should have looked further into how it's really supposed to be installed on the gun.