I'm working through an issue with the POI changing on my 25 WC. I can have it dialed in and shooting one ragged hole groups out to 60yds. Put it up for the day, take it back out and it might shoot a 1 1/2 high and an inch to the left the next day. I pulled the Hawke SW off and replaced it with my SWFA 12X and I thought that took care of it but it drifted off of zero again today. The velocities have been very steady, shooting MK1's around 875. I think this started after I had the barrel and shroud off. Today I noticed that the shroud bushing closest to the breech or air tube clamps was up all the way against the air tube clamps. I never loosened this bushing on the barrel and I double checked the set screw impressions by looking down on top of the receiver into the hole where the set screw secures the barrel. It looked perfectly aligned. Just wondering if changing temps might induce POI change with the bushing snug against the air tube clamp.
My thinking is that possibly the bushing being up against the air tube clamps might some how be tensioning the barrel and interfering with it's free floating. I slightly adjusted the barrel outward so that a .015 feeler gauge would slide in behind it. So my question is are you guys seeing a slight gap between the bushing and the air tube clamp? I haven't re-zero'd yet to see if that makes a difference so the jury is still out.
Another question on the shroud. On my gun the shroud screws onto the rear bushing and then on the muzzle end the air stripper with a shoulder on it screws onto the end of the barrel. I do know that the air stripper never bottoms out on the 1/2 X 20 barrel threads but stops turning and tightening when the shroud mates up to the shoulder on the air stripper. Makes me wonder if it's designed this way which is actually tensioning the majority of the barrel. If the shroud was a tad shorter the air stripper would tighten down on the barrel first and not hold that tension on the barrel.
Hopefully getting the bushing away from the air tube clamp MIGHT help. I would appreciate it if someone would check there bushing to clamp gap if any. Preferably on a unmolested gun.
Jimmy
My thinking is that possibly the bushing being up against the air tube clamps might some how be tensioning the barrel and interfering with it's free floating. I slightly adjusted the barrel outward so that a .015 feeler gauge would slide in behind it. So my question is are you guys seeing a slight gap between the bushing and the air tube clamp? I haven't re-zero'd yet to see if that makes a difference so the jury is still out.
Another question on the shroud. On my gun the shroud screws onto the rear bushing and then on the muzzle end the air stripper with a shoulder on it screws onto the end of the barrel. I do know that the air stripper never bottoms out on the 1/2 X 20 barrel threads but stops turning and tightening when the shroud mates up to the shoulder on the air stripper. Makes me wonder if it's designed this way which is actually tensioning the majority of the barrel. If the shroud was a tad shorter the air stripper would tighten down on the barrel first and not hold that tension on the barrel.
Hopefully getting the bushing away from the air tube clamp MIGHT help. I would appreciate it if someone would check there bushing to clamp gap if any. Preferably on a unmolested gun.
Jimmy
