I've posted this elsewhere, but what the heck...
I have been have some troubles with my 1944 No.4 Mk.1 (FTR 1949) with some vertical stringing. The width of groups was good at 100 yards - 1 to 1 1/2 inches, but the vertical displacement was 5 or 6 inches, so zeroing in this old girl was difficult. I did slap on an S&K instamount and a Tasco Pronghorn scope (my eyes are not as good as they used to be, and the scope is good enough for my purposes) a while ago, but I knew that they were rock solid and were not the cause of the problem. A quick search here and I had my answer - bedding issues. After some experimentation with cork bedding at the muzzle to produce the correct 3 to 7 lbs downforce, and liberal applications of linseed oil, I went back to the range. Bugger. No real difference. I then thought about things and decided to try cork shimming (as a reversible option) between the forend and the receiver behind the trigger and, please don't hit me, plastic shims glued (but easily removable) on the receiver draws.
I went to the range yesterday to see the results of my efforts. I was shooting Sierra MatchKing 174 gr HPBT with 38.3 gr Varget using Prvi brass and CCI primers. Weather was gorgeous with no wind, good sun, 60 degrees F. Shooting position was sitting using a shooting rest under the forend on a concrete bench. Point of aim was a little cross under the target.
This is the result with the first 5 rounds yesterday at 100 yards -
Arrgghhh!!!! The dreaded vertical stringing. The hole on the right was a warm-up shot. Just in case I was messing up, I tried another 4 rounds (was getting low on ammo), same point of aim, to try and get a consensus of opinion -
Now I am thinking "what is going on???". The answer? The rifle had to settle into the bedding work I had done. Point of aim was dead centre on the middle of the cross. At this point, I had not adjusted the scope whatsoever, so it was a total fluke that my prior zeroing attempts were spot on. I was just slightly pleased at this time.
Next was trying the rifle out at 200 yards, point of aim = centre of target -
The 2 shots high and left were after roughly adjusting for changes in bullet trajectory, the second 2 rounds (the last of my handloaded .303) were spot on.
I would consider that a good day at the range, especially as I was also shooting my old Mosin Nagant 91/30 that I have been working on (cork shimming in forend, metal shimming work on the trigger), and the grouping size is down to 1 1/2" at 50 yards using iron sights (it was 3 inches). More work is needed, though.....