I am new to bigbores and am getting used to my .458WM.
Today I did six three-shot load development groups sitting off the bench at 80 meters.
I failed to post a pic. so I'll have to describe them.
Bullets were A-frame 400grs and Rem. 405grs. Powdercharges in 1 grain increments.
All groups are large, just under 2,5", equal in size and 4 out of six have a vertical string.
I was expecting better or at least some difference between groups.
Can the vertical stringing be caused by me not taking the recoil in the same way each time?
Is my problem me (shooting), the loads or the gun and how do I proceed?
All advice is wellcome!

Snowhound,

Please give us the loads you used, the rifle, scope, rest and set up. There are many reasons you could have large groups which include the rifle, the scope, the rest, the shooter and the load.

Look forward to more detail. Kudude

Yes, your vertical stringing may be caused by how you're set up on the bench. First of all, are you hunkered low on the bench? Do you have your support hand(left if right-handed) holding the fore-arm when shooting it? The best way to shoot biggies is to sit as upright as you can so recoil won't smack you. When you're down low, it can be outright brutal, especially if you're not accustomed to it. Holding the rifle with both hands controls how fast the barrel rises in relation to how the bullet exits the barrel. It doesn't have to make sense right now but it'll come to you after a few hundred full loads. Just keep at all and say to yourself that you really love getting bruised up.

Thanks guys!
Details: Win 70 Classic Safari Express, Leopold 2-7 in Leopold QRW mounts, Loads are Norma brass with norma 201 powder and CCI primers.
Powdercharges were 75,5grs, 76,5 and 77,5grs. No pressuresigns.
The bench though is not the best. It is a low wooden bench with sandbags.I get the gun up as high as possible and try to sit upright though I may be just a tad hunkered down. I use a 1" thick neoprene kneepad between my shoulder and the but. I grip the forarm with my left hand just in front of the mag well behind the sandbag.
Recoil isn´t a problem and I am not flinching although I have to focus on this. After followthrough I am reasonably back on target but not always the same every time.
Maybe the best place to start is to get the bench set up better.
What bummed me was that two different bullets and three different charges gave identical groups.

By the way, the groups are not great but they will have to do for this years moosehunt, that starts in less than two weeks, as long as I limit shootingdistance.

Finally mastered the "post image" thing!
This is what the groups look like.
Top row is Swift A-frame 400grs. Bottom row is Remington 405 grs.

I think I'd try 500gr projectiles and another powder as well. And if your bench is too low how about a lower seat?

Snowhound,

Can you tell us the order of the rounds in the various targets?

If not, retest and do the following:

1-Get has straight up as you can, and concentrate on getting your eye directly behind the scope;

2-Make certain that the sling swivel is not contacting your rest;

3-After you resize your case and before you prime clean the inside of the neck with alcohol to remove any lubricant;

4-Clean the primer pocket before re-priming (if you weren't using Norma brass, ream the inside of the primer hole);

5-Inspect your barrel and make certain you have not burrs on the crown;

6-Torque your actions screws down with the forward screw and tang screw really tight and the center screw just tight enough to hold and not loosen;

7-If the foregoing has not solved your stringing, and your model has the forearm screw that sets into the barrel, try removing it and saving it in a safe place; Fire some strings and see if it strings without the screw and if that doesn't work, try some with the screw tightened down; and if that doesn't work, with it barely tight. Mod 70 rifles are finicky about this screw. If it works better without- cut one off and epoxy it into the hole for looks.

Get back to us on how these suggestions work. Kudude

The big bore rifles will exaggerate any mounting problems you have. You may be occasionally jerking the trigger also. I shoot a lot of hard kickers, the key is to shoot it often, but not a lot at a sitting.