Gunsmithing Skinney Sporter Weight Barrel

mdesign

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So my friend has a Wby Mark V chambered in 7RM that has a very thin barrel contour and the accuracy really suffers by the 3rd shot. For cold-bore accuracy, it's an solid inch gun @ 200yds but if you shoot three shot groups the accuracy is close to 5" @ 200yds. It has an HS Precision stock and the bedding is pretty good, he's switched scopes and it does not matter, 1st shot is dead on, 2nd shot is close, 3rd shot is really out there.

I told him it sounded like the barrel is heating up so he waited 5 minutes between shot and the group comes right in.

Is there any tricks to making a barrel like this better? The barrel is free floating and I considered a pad up front to see if it helped but pads usually cause other issues from my experience. Any idea's out there as to what he might try?
 

GrantA

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The OP says this rifle produces acceptable groups when the barrel is allowed time to cool between shots. How does that point at the action? This is simply a downside to a lightweight barrel. I'm in the same boat, planning to rebarrel with a heavier profile.
 

Bluejazz

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If this is a hunting rifle, then you are fine. It's the first shot that counts. Never have had to shoot a group on a game animal.
I can't remember when I have ever taken a follow up shot.
So,point is, first shot cold bore placement is priority in a hunting rifle.
If he wants to shot groups, get a heavier profile barrel.
 

jsthntn247

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If this is a hunting rifle, then you are fine. It's the first shot that counts. Never have had to shoot a group on a game animal.
I can't remember when I have ever taken a follow up shot.
So,point is, first shot cold bore placement is priority in a hunting rifle.
If he wants to shot groups, get a heavier profile barrel.

I agree, if you can make the cold bore shot count on a hunting gun, that's all you need. However, if groups are opening up from 1 to 5 inches by 3 shots, there is a problem elsewhere besides the thin barrel. This is the whole reason behind truing an action. When the action face, recoil lug, and barrel shoulder and threads are not trued and absolutley flush with each other, heat causes them bend and yaw on each other at their uneven points which causes poi shifts. When it cools down, it goes back to shooting, this is what the op is experienceing. Lowlight has a training video somewhere on here about heat not causing point of imapact shifts on well put together rifles.
 

dakor

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If he is reloading his own ammo have him try this. Take the load he is using and load up 3 separate 3 shot groups. The first group of three have him move the bullet .003 closer to the lands than the original and the next group of three .006 closer to the lands than the original and the last group of three .009 closer to the lands than the original. So the last group will be .009 closer to the lands than the one he is shooting now. Now shoot each group of three one at a time like you would when working up a load and see if one of them tightens the group up more than the original. If this does not then the simple answer is let the barrel cool more and some barrels just do not shoot well when they are hot. I have also seen this in custom rifles as well so re barreling to a bigger barrel might not take care of the issue.
 

Greg Langelius *

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Couple of ideas.

I am assuming that that the barrel is floated, and that as it heats and the third and successive shots move away from the first, they also move in a consistent direction. Such a condition may find remedy from a barrel channel pad. I would try some form of firm elastic support, like neoprene foam (I.e. Foamies Craft Foam) out at the end of the barrel channel. The pad shoud exert enough upward force to override any usual barrel vibrations. Very often this will also require load redevelopent.

Alternatively; if the barrel is not floated, try some temporary shimming under the receiver so it lifts it and disengages the barrel from the presure pad. If this temporary measure produces improvement, remove the barrel channel pressure pad.

Another approach would be to develop a load according to the preferred shooting conditions. If the preferred condition is sustained fire from a warm-hot barrel, then load testing shoud disregard any cold barrel shots.

Greg
 
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rpk762

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I have a 7mmSTW in a Rem 700 in what is called a mountain rifle. In my rifle the barrel was in contact with the stock. I had to clear out a channel for the barrel and now it shoots consistent. You may want to look at that.
 

MTyotehunter

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if the barrel is not touching the stock I would say you have a stressed barrel. bedding action and barrel might help this but im thinking you may want a new barrel. Dont let anyone tell you its just a light barrel problem, being on the light side makes the problem worse but I have light barreled rifles that will shoot a under 1/4moa running 5+ round strings. Your problem is common with factory rifles that they tried to build TO FAST.... its irritating i know
 

Killer Spade 13

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Barrel is the problem. Heat sink and dissapation. Weatherby's are known for this issue. Had a friend with a Mark IV 300 mag. You could NOT shoot over 3 rounds in a 2 minute time cycle without the barrel moving. I would NEVER own one. Pretty, nice wood, shiny stuff . . . guns that are made for jerks with too much money and not enough hunting sense.