What is causing my Ruger Mark II (25-06) rifle to shoot a vertical group? I have floated the barrel and tried a few different loads, but still get a vertical group of close to 2" at 100 yards. I have been told that the barrel is bending as it heats up and can't be fixed. Any other suggestions?

I used to shoot .22 LR off a bench at a Boy Scout camp (range was 50 ft). A vertical group there meant that you needed to work on your breath control. Side to side groups was a problem with trigger pull. BTW the standard for accuracy there was 10 shots that could be covered by a dime.

Vertical grouping generally means more load development is required (assuming that the other items you mentioned are not a factor). The idea of load development is to find a load that takes advantage of the natural barrel harmonics. In your case, it is possible that you have the best load for that powder/bullet combination and so you should try another. Thus it is possible that a 2" group is the best that this combination can achieve. YOu might want to try "the Audette method" of load development which might save some time, but first I would try to see just what kind of accuracy your rifle is capable of. Have you used a chronograph? You might want to use one to see what velocity variation you are getting with your loads. If you have a best load, try weighing the powder charges individually and see what kind of group you get. Ultimately, the bullet is probably the most important factor of all the components, so, if you are just looking for accuracy, try match quality bullets.This won't help you for hunting, but generally people want to brag about how accurate their rifle is!
Peter

if you are getting vertical most of the time it is in the amout of pressure you are pulling the rifle back into your shoulder.if it isnt the same every shot you will string em up and down. try a group or two free recoil and see what happens.let the gun just barely touch your shoulder and squeeze it off.

If the action screws are to loose of to tight it can add to stringing. If every thing metioned above is in line you may try glassing, and/or pillar bedding the action. You can change the action screws to hex heads and use a torch wrench set at say 10 fps.
But just like mentioned above you should check technec and loads before the action or the crown.

If you've eliminated all the common gun problems, including action screws and bedding, and scope, you might try reducing the propellant a grain or a half grain.

There's an old timer at our range (older than me, if that's possible!) who swears he corrects vertical stringing by reducing the load a tad. Horizontal stringing (if the most common problem of the shooter is eliminated,) he increases the load a bit. I've had success with that method a time or two. It's worth a try!

Take a buissness card, piece of cardboard, or something similar and fold it up untill when slid between your barrel and forearm it creates a little upward pressure on the bbl. Take your gun to the range and test fire varying the amount of pressure between shot strings. This is a cure I have used many times over the years on different rifles that had accuracy problems, some bbls just like a little pressure at the end of the forearm like this. If this cures your verticle stinging then you can use some bedding compound and build a pad at the forearm tip for a permanant fix.

Steve:I'll muddy the water even more but I'll bet this may solve the problem. In "Aqua-Field World of Hunting and Shooting" July 1995 issue an article by Dick Wright, benchrest match shooter, and specialty tool source(White Tail Design and Engineering, 9421 E. Mannsiding Rd. Clare MI 48617) for precision shooting states that verticle stringing is the result of improper bullet seating depth. Proper seating depth for the bullet/load/rifle combination will shrink the group. Change bullet seating depth in .005" increments,starting with just off the lands, especially if it's a hot load, and back off in .005" steps untill you hit that "sweet spot". I've done this and it has given amazing results. I discovered this independently while working up loads using Barnes bullets from my .416 Rigby down to my .257 AI. Hope this helps.

Steve,

Make sure everything is consistent when you develop loads. Including the way you hold the rifle or the force you press it against the sandbag. When the rifle fires, a tiny amount of muzzle rise is included in the bullet's movement. I have a Mauser that will shift POI(vertically) when I press it against the sandbag or when I rest a different point on the sandbag. It is also advised that the front sling swivel stud do not touch the sandbag or it could change POI(vertically).