Grouping interpretation help

[mshelton]

I'm hoping to get a little help in figuring out what happened today, kinda new to the longer range shooting and I'm still learning.

Started off today setting up a 200yd target across an old pasture I have the good fortune of being able to shoot at. I loosened the screws holding my action in and tightened them back up. I walked down to the target between each group to take a look at them and to give the barrel a little cooling time.

My first group was 5 shots strung vertically, a group about 3" up and down, 3/4" left to right and I chalked it up to factory ammo (Hornady 32g Vmax) and a clean barrel. Next group, 3 shots dead on, a group of about 3/4" even held one off a bit for a breeze that came up. Should have finished the group but decided instead to shoot a couple golf balls I had set down there, figuring the rifle was on. Decided next to try the bipod instead of the rest. I knew my POI would be off, group was high right and about 2". Shot another group and got the same results. Decided to go back to the rest and bag, and I got the same results for 2 groups, decided to do a quick cleaning of the barrel and loosen/tighten the action screws. Same results, large group high right for a couple more groups.

It was in the 90s here so I decided to pack it on for the day and head home, but I can't figure out what happened to cause that kind of shift. I know I'm using factory loads and maybe I found 3-5 there that were consistent but from centered to right doesn't make sense to me. I know the rifle could use a bedding and this may help it out but is there anything else I should be looking at (well besides handloading, which is coming )?

Thanks

[Ruger1]

I've never heard of loosening and tightening action screws as a matter of cooling a gun down or when shooting groups. From your comments that was what I assumed you were doing. I know that if you don't use a precise sequence for tightening those screws that can create some issues. I may be really missing something in my practices but why lossen the screws?? I'd try it again and do nothing more than clean and let it cool with the action open.

[mshelton]

The loosening / tightening of the action screws is something I've always done with my rimfires before I start shooting them. I don't do it between groups, just the start. The thinking behind it is that the gun was last disassembled in a climate controlled environment then brought out into hot and humid weather (or anything) so the stock may have shifted creating unwanted pressure. So I just do a basic disassembly and reassembly to help get the gun adjusted to the climate.

[jo191145]

Just a thought.
Its possible your scope is reacting to the heat of the sun. Unlapped rings can put pressure on the scope tube. Add some heat from the sun and that can cause your scope to flex further.

Might think I'm nuts but I've seen this happen with a glued in custom PPC with presumably lapped rings and Weaver 36X.
Possible the barrel and action were warping between relays but my money is on the scope tube.

JMO No need to mess with the action screws. You'll cause more trouble in an unbedded rifle messing with the screws than humidity can.
As long as they're tight and stay tight your good to go. In an unbedded or improperly bedded rifle it can sometimes take quite a few shots for the action to settle down (if at all )