My 338M took an untimely turn for the worse today. It started double grouping abot 1 MOA at 800 yards. Any guesses? I leave on a cow elk hunt in a few days........I am hoping scope. Anyone seen any other causes of double grouping?
Scope or Bedding?
- Thread starter eddybo
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Joel Russo
Well-Known Member
What's it doing closer in?
Swap out the scope with a known good one and see what it does.
Swap out the scope with a known good one and see what it does.
Thanks for the reply Joel. I swapped scopes but ran out of light before I could shoot again. I have no idea what it is doing closer up.
I knew something was not right last time I took it out,but asumed it was the load. I shot today expecting it to be right since I went back to my old load which has always shot lights out. No such luck. The first shot was perfect. I thought things were back on track. Second shot gave a lot of vertical. I stared tinkeing with the loads to try and get the vertical out. I played with the load a while then realized I had two decent groups about 8 inches apart.
I checked tightness on everything including the action screws and then scrubbed it good and tried again. Same scenerio one shot goes to point of aim the other goes MOA high and 1/2 MOA right.
The only causes I know that will cause double grouping are bedding and scope problems. I know the bedding on this gun has been perfect, and cannot think of a reason that would change snce I never take it out of the stock. This 338 AM has always shot better than this regardless of te load, so I am hoping scope problems explain it.
I knew something was not right last time I took it out,but asumed it was the load. I shot today expecting it to be right since I went back to my old load which has always shot lights out. No such luck. The first shot was perfect. I thought things were back on track. Second shot gave a lot of vertical. I stared tinkeing with the loads to try and get the vertical out. I played with the load a while then realized I had two decent groups about 8 inches apart.
I checked tightness on everything including the action screws and then scrubbed it good and tried again. Same scenerio one shot goes to point of aim the other goes MOA high and 1/2 MOA right.
The only causes I know that will cause double grouping are bedding and scope problems. I know the bedding on this gun has been perfect, and cannot think of a reason that would change snce I never take it out of the stock. This 338 AM has always shot better than this regardless of te load, so I am hoping scope problems explain it.
Joel Russo
Well-Known Member
I'm assuming you pulled the barreled action out of the stock and inspected the bedding. If there are no surprises there, I would certainly be looking at the scope.
What scope do you, or did you have on it?
May want to walk it in to about 300 or so and shoot it there.
Let us know when you get enough light to shoot it again.
What scope do you, or did you have on it?
May want to walk it in to about 300 or so and shoot it there.
Let us know when you get enough light to shoot it again.
royinidaho
Well-Known Member
I doubt its the bedding, but it can't be left out of the investigation.
The last time that happened to me, it was base mounting screws being a bit loose. The time before that it was the two-bit windage adjustment on the redfiel/leuy bases that failed.
If the rifle was made where I think it was, the scope itself or something to do with the scope mounting system, namely the screws, would be my top suspects.
I also suppose the mounting screws are of the larger variety???
Let us know of your progress.
The last time that happened to me, it was base mounting screws being a bit loose. The time before that it was the two-bit windage adjustment on the redfiel/leuy bases that failed.
If the rifle was made where I think it was, the scope itself or something to do with the scope mounting system, namely the screws, would be my top suspects.
I also suppose the mounting screws are of the larger variety???
Let us know of your progress.
somthing to look at might be the port clearances on the muzzle brake.
I have recently become aware of an accuracy problem that develops in some braked rifles, the leading edge of the baffle bore holes, erode from the forces of the gas jet. As this happens it roles the edge into the clearance hole, causing the clearance to tighten up and create accuracy losses that are otherwise unexplainable.
Inspect the port holes very carefully, it will be obvious with a careful inspection if this is the problem. The quick fix is a brass rod with a split in it, wrapped with 320 grit emry cloth, and spun in a drill, as you polish off the burs. Once this bur is removed, it rarly comes back because the 90 degree edge that roled in is now removed from the erosion and the subsequent polishing.
Before doing this protect your crown with a mechanical barrier so you don't hit it with the abrasive.
I have seen this on a couple guns that came in the shop and then recently had one of my brakes do the same thing. I now have been sending out all my brakes for heat treat, hoping this helps the situation if the brakes are up to 32-34 rockwell.
I have recently become aware of an accuracy problem that develops in some braked rifles, the leading edge of the baffle bore holes, erode from the forces of the gas jet. As this happens it roles the edge into the clearance hole, causing the clearance to tighten up and create accuracy losses that are otherwise unexplainable.
Inspect the port holes very carefully, it will be obvious with a careful inspection if this is the problem. The quick fix is a brass rod with a split in it, wrapped with 320 grit emry cloth, and spun in a drill, as you polish off the burs. Once this bur is removed, it rarly comes back because the 90 degree edge that roled in is now removed from the erosion and the subsequent polishing.
Before doing this protect your crown with a mechanical barrier so you don't hit it with the abrasive.
I have seen this on a couple guns that came in the shop and then recently had one of my brakes do the same thing. I now have been sending out all my brakes for heat treat, hoping this helps the situation if the brakes are up to 32-34 rockwell.
flyin lizard
Well-Known Member
Good to hear you found the culprit , now we all expect to see successful elk hunter pics..
