Joe ...
Here are some suggestions from Speedy Gonzalez on combating vertical. Art
Tips on Vertical Problems
1. A lot of rifles are muzzle heavy. Some rifles have too heavy a barrel and this causes vertical problems, especially those who shoot free recoil
2. Firing pin coming out of hole in bolt in the cocked position. This will cause poor ignition. Take bolt out of rifle and look in firing pin hole. If you cannot see entire end of firing pin it has come out of the hole.
3. Firing pin dragging in bolt or shroud. Listen to the sound when you dry fire. If not the same sound each shot something is wrong.
4. Trigger sear too much spring. Hold trigger in firing position and push down on sear with your thumb. If it is hard to push down, this will cause vertical problems.
5. Firing pin spring too weak or too strong will cause vertical problems. If you think this is the problem change springs and see what happens.
6. Tightening front sand bag too tight on stock. When you try to pull rifle back by hand and rifle feels like it is stuck in the bag it is too tight. Rifle should move in sand bags evenly, not jerk or chatter when pulling back by hand.
7. Action not level with top of stock running down at muzzle end. Rifle will recoil up at butt end causing vertical.
8. The load that you are shooting can too light or heavy and can cause vertical problems.
9. Bench technique not same every shot. One example, shoulder against stock one shot and not the next.
10. Bad primers – if getting vertical try other primers.
11. Bad scope, if scope is bad from shooting vertical, if you change your load in anyway and vertical goes away it is not your scope.
12. Rifle not balanced, it does not recoil right, jumps in bag. If rifle is built properly this will not happen.
13. Some stocks are very flexible. This can cause vertical.
14. Front sandbag too hard. I personally have never had a rifle that will shoot consistent with a rock hard front sandbag. It always causes vertical or other unexplained shots.
Source:
http://benchrest.netfirms.com/Benchrest Basics.htm
