I have a question for you guys. I had a crappy time out at the range last week shooting some crap UMC ammo out of my AR (never again). The rounds were getting very inconsistent at 300 yards when the day prior I way hitting my 7" steel plate every other round. I noticed later when I was going to clean the gun, that I had a good bit of black gas residue on the front and back of the barrel surrounding the gas block (railed not a post sight). I've never had this issue before and was wondering if a gas leak would cause any of the issues I was having relating to accuracy?