Hey guys,

looking for some help on this one. My buddy shoots a Christensen Arms Rem 300 Ultra Mag and is having some significant "drifting" on his groups.

The last 3 times he's shot, his groups started out in the extreme lower right hand side of his target and drift up toward the extreme upper left hand side of the target. He takes 3 shots, and then we look at them very carefully through the spotter. After a few minutes, he takes a few more shots, and the group has creeped, up and to the left. This continues with each of 3-5 groups that are shot.

We are shooting hand load 180gr Accubonds, if that helps anything. We have not adjusted his scope at all and we are shooting from a solid dead rest on a table with little to no wind. These shots were all taken at 200 yards.

I've attached a few pics of some of his targets to give you more of a visual.

Any suggestions as to why this is happening and/or any suggestions for fixing the problem, would be much appreciated?!?

copple2

Have you tried a different shooter ?
A 300 RUM is a great flinch inducer.
Try a lead sled first, check all screws for proper torque, then a different scope. Get a box of factory ammo and see how it does.
Bedding should not be an issue but......

I owned a 721BDL 300 RUM for 7 shots. Then it went away and so to did the headache and sore jaw. Just a nasty gun. Can shoot my 30-378 Accumark as long as I want with plugs AND muffs and suffer no beating. It is also scary accurate.

I admire your buddy's perseverence in sitting behind that cannon for that many shots!

The fact that the direction of drift is more or less consistent, I would rule out any ammo issues, and think that scope/mount problems are also fairly unlikely.

It looks to me like a bedding/barrel contact issue.
Was the barrel supposed to be free floated? If so, a quick run through with a thin piece of paper between barrel and forend should confirm it.

If the drifting is due to barrel heating, confirm it by allowing enough time between shots for the barrel to cool down completely- not just a minute or two between shots, but completely, maybe 10-15 minutes or so depending on outside temperature. If several shots then group, you have an answer to one possible problem. As a barrel heats up, it expands, and if there is uneven contact with the stock, barrel vibrations will change, often unpredictably. With the amount of powder that .300 burns, and the velocity it generates, a large amount of heat is created, in a big hurry.

I have had several rifles in the past that exhibited vertical stringing as the barrels heated up. In every case, relieving the forends so that the barrels were completely free-floated immediately solved the problem- but none of them strung shots as badly as your buddy's.

That is about the minimum I would call a group. Bigger than than and they get to be described as patterns.

I would put a competent shooter behind the gun and try it again. If it does show a tendency to drift then, float the barrel. But, if it doesn't shoot any better than that it hardly matters.

He has not tried a different shooter yet, as that is a great suggestion. I'll get him on here to read this and we'll get the "floating barrel" checked as well. Thanks for the suggestions guys...keep 'um coming!

copple2

any more suggestions?

copple2

Barrel heating up...

I would suggest you try another proven scope. That could be a subtly going sour scope.
Make sure the rifle is in exactly the same place on the bags. Touching nothing hard etc.
Check all of the action, base and ring screws, etc.
And, yes, it could also be the shooter, but it appears to put most them in a good group, but the zero shifts some. My suspect is the scope. E

i'd check all the screws, including the base, and put a proven scope on it.

it's a starting point to make sure all is well, then i'd get another person to shoot it, just to see if there is a difference in the groups.

come on guys a 300 rum isn't that bad of a kicker.

it's loud, but mine doesn't hammer me al that bad.
at least less, than my 45-70 guide gun !

It's easier to confirm barrel contact on heating issues by doing the paper test while the barrel is hot and throwing shots. Doing it this way also tells you exactly where the contact is. I don't use a thin sheet of paper either; I want at least 2 dollar bills worth of free float.

Any parallex issues with the scope?Rick.

I thought those carbon wrapped barrels were supposed to dissapate heat,not walk.....but that's pretty bad.

In my mind the fact that the rifle "starts" in a consistent spot,and "walks" predictably,says it is not the scope, but I could be wrong and this is easily determined by swapping the scope.

If it behaves the same, then it's obviously a rifle problem.I'd return it to Christianson.......

+1

My thoughts exactly. Two types of barrels that Christianson makes, wrapped from factory turned down barrels and wrapped from custom barrels...difference in price, also.

Barrel walking around could be heat warpage and/or the barrel is not screwed in tight enough.

Loose scope mounts usually leads to huge groups.

good luck!

Sounds like what my 7mm RM Ruger M77 was doing when I first purchased it in 1982. It would start out ok but the longer I shot the further up and to the left the impacts went.

I floated the barrel and have not had a problem since.

I'd go to the manufacturer. For that much coin they should take care of it. Assuming of course it still does it with another shooter and scope.