I got a new scope so I put it on my deer rifle. I put my old scope on my muzzle loader for the time being. It's a Redfield 3-9 30 mm, about 15 years old. Question is, it shoots about 18 inches to the left. I've walked it over to the right but now the adjustment screw is getting tighter. I'm still about 5 inches off @ 50 yds. Do I keep adjusting? Why did the adjuster tighten up?