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Help with strange grouping

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Old 04-11-2013, 12:19 PM
Silver Member
Join Date: Aug 2008
Location: Forks, Wa
Posts: 138
Help with strange grouping

I am shooting a custom 338 RUM built by Mcwhorters... Nice gun... It shoots pretty well overall...Having some very funny grouping. though... 2 in 1 hole and a slight flier...doesnt matter what order i shoot them in either...every bullet, Accubonds, Bergers, ttsx..all grains of powder, different powder ,and different primers...funny thing is every group is an inch to 3/4.... and primarily in the same spot... 3 inches High at 100.... I can shoot 3 different loads with differnt powder and weight bullets and they are all within an inch of eachother.... Seen something like this before, and Knew it was a bedding problem.. not here though.. gun sits in a Macmillan, edge stock custom from Mcwhorters, Dont see any Pressure issues either.... ANYBODY GOT ANY IDEAS ,
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Old 04-11-2013, 01:13 PM
Platinum Member
Join Date: Dec 2011
Location: Vandergrift PA
Posts: 1,263
Re: Help with strange grouping

Bad or improperly set up scope??? Either that or a bedding issue?? can you post up some pictures of the groups??
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Old 04-11-2013, 07:36 PM
Bronze Member
Join Date: Feb 2011
Location: Western NC
Posts: 83
Re: Help with strange grouping

First thing we need to know is how you are shooting these groups. Are you letting rifle cool completely between each shot or are you cooling between groups? Clean/Dirty/Fouled barrel? Rest? I would start by checking out your scope really well. If that doesn't help you may want to try adjusting torque on your action screws. I had a similar problem to this once, found out I had been over tightening my rear action screw. Started using a torque wrench and set it the same every time I take it apart. Even though it is in a custom stock If it is not skim bedded I could possible see this happening.
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Old 04-11-2013, 07:40 PM
Silver Member
Join Date: Jan 2013
Location: Kansas
Posts: 201
Re: Help with strange grouping

Is the first shot the flyer or the last shot?
Those who would give up Essential Liberty to purchase a little Temporary Safety, deserve neither Liberty nor Safety.
-Benjamin Franklin
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Old 04-12-2013, 05:45 AM
Platinum Member
Join Date: Jan 2008
Location: Northeast
Posts: 2,420
Re: Help with strange grouping

Its quite possibe that POI could be the same for various loads snd bullets, particularly at 100 yards. As to the flyer, I would try shooting at 200 yards. It might be caused by parallax effects. Also check the scope mounts, and perform a box test. This should help rule out scope effects which I have seen produce similar results to what you are describing. I have also seen this with a faulty shooting rest system, ie bipod bounce, or a loose rifle rest, hold, etc.

"Let us speak courteously, deal fairly, and keep ourselves armed and ready"-T. Roosevelt
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Old 04-12-2013, 06:28 AM
Silver Member
Join Date: May 2010
Location: S.C.
Posts: 215
Re: Help with strange grouping

In addition to the other suggestions, I would try a five or ten shot group and see how or if the grouping continues to grow.
Good luck
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