Group and reloading question?
Remington Sendero in .270 Winchester
Weaver V16 scope
I loaded some SST's I got a few months ago 135gr. I'm a half grain below max with H1000 powder, 63.4 grains, shooting CCI mag primers, out of Remington cases(3 handloads on these cases and one factory). I turned the case necks after the second loading just to uniform them up. Seated the bullets to the cannalure, but didn't crimp them. All the primer flash holes are uniformed and centered, the brass all is within 1 grain of one another. Everything seems to be in order for some decent accuracy.
I got the range mowed today, so I shot 100yds first, got a one inch group out of 3 shots, 2 overlapping and one blowing it out, but I didn't feel I flinched at all. Fired 7 rds at 300yds at a steel plate, had a 1/2" dot to use as an aimpoint. I put in 2moa elevation and shot for the dot, knowing it should drop about 6" at that range. It was dead calm this evening. The first two shots hit 1.5" apart 7" low and 2" right of point of aim. Let the gun cool, fired the third, it hit 6" low and 1/4" right of POA. Next shot hit right on POA, so I think I jerked it. The next two shots I heard it hit, but couldn't find a mark on the fresh paint, the 7th shot flew into roughly the same area as the first two shots, actually made a 3" 3 shot group at that point. One on the POA which was probably me. I went to the steel to find my other two and found them touching the 6" low 1/4" right mark, those 3 shots where in right at 1"(strung horizontally which means I wasn't holding true) at 300yds.
Something is throwing off these loads, some of the brass is coming out dinged up on the bases, I actually find flakes of brass in the bolt face; but it only rubs one side of the base. Is it inconsistant pressure? Out of true lugs? At 100yds you can't make distinctions but at 300yds it really showed up. It looked like two totally different groups, cept my called flyer.
I'm going to pick up another box of remington corelokt factory and see if it holds to 3/4moa out to 300yds like it did at 100yds, since it is much milder loading than what I am shooting. Should pick up some H4831 on Monday that a friend is giving me to try, see if it makes a difference. But I have a feeling something else is wrong, makes me wonder with the group moving horizontally if it isn't the lugs and pressure difference, it just bounces a little harder because of a slight pressure rise.