Husqvarna groups moving to the left?

Cdn303

Cdn303

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Hello all,

I have a Husqvarna 1640 in 30-06. It is wearing a Redfield Revolution 2-7x33 duplex reticle mounted with 'Low' Burris Zee rings, leveled to the receiver, all screws are tight. I am shooting Remington Core-lokt SP/PSP at 150gr, 165gr, and 180gr. All shooting was done at 100yds using a Lead Sled. There was a slight breeze from left to right blowing toward the target. Rifle bedding seems to be OK.

I zeroed it using 150's, 1 inch high at 100yds (bottom left target). When I tried shooting the heavier bullets the groups started migrating to the left. First the 165's moved about 2 inches over, then the 180's moved right off the paper. This happened a couple of weeks ago with the same deviation, but I forgot to save the targets.

Scouts honour, the 180's put 2 rounds into the same hole. The lower hole is elongated ever so slightly when measured.
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I can't for the life of me figure out why it is doing this. Any thoughts?

Cheers
 
Is the barrel free-floating (or at least supposed to be)? Might be a contact point that as the barrel warms up it is causing the deflection. Try the 180s on a cold barrel then the 150s after it has warmed up and see if the issue occurs again on the later shots.
 
A barrel can whip left to right just as easy as up and down. I see it frequently on free floated barrels while just working up loads.

When changing bullets weights the POI can end up pretty much anywhere, or not change much at all. There's not a lot of rhyme or reason to it.
 
how is it with the 150's now? is your scope falling apart on the inside? fair bit of recoil and lower end scopes can get eaten up pretty fast
 
Barrel harmonics with different weight bullets (coming out a different velocities and with different pressure curves in the barrel) etc etc .. BUT another rare possibility is a muzzle crown that is not perpendicular to the bore.
 
I have that model rifle and it puts 150, 165 and 180 grain bullets into the same group.
It didn't, until I bedded the barrel, as I usually have to do on bolt action rifles.
Take the stock off. Look for any shiny spots that have been hitting and sand them out.
It now needs a saddle at the front of the stock to put pressure on the barrel. It should take about six pounds to lift the barrel from your saddle. The saddle can be folded paper to try it and when it is right, make something permanent, with no side pressure on the barrel, only straight up pressure.
I have been doing this for many years with great success, thus I am not going to get into any discussion the merits of it.
 
Dogleg said:
A barrel can whip left to right just as easy as up and down. I see it frequently on free floated barrels while just working up loads.

When changing bullets weights the POI can end up pretty much anywhere, or not change much at all. There's not a lot of rhyme or reason to it.
Click to expand...

Like Dog said, it can happen. My .308 will move the POI a bit side to side depending on the bullet weight. It's not as drastic as what you've got (normally under 2" difference at 100m) but it suprised me the first two times.
 
H4831 said:
I have that model rifle and it puts 150, 165 and 180 grain bullets into the same group.
It didn't, until I bedded the barrel, as I usually have to do on bolt action rifles.
Take the stock off. Look for any shiny spots that have been hitting and sand them out.
It now needs a saddle at the front of the stock to put pressure on the barrel. It should take about six pounds to lift the barrel from your saddle. The saddle can be folded paper to try it and when it is right, make something permanent, with no side pressure on the barrel, only straight up pressure.
I have been doing this for many years with great success, thus I am not going to get into any discussion the merits of it.
Click to expand...

Yup. Me too. I have an old jacket made with paper thin leather that I've been cutting up over the years for the same purpose. If I want to get fancy, I use some of that cylindrical white eraser that's about 3/16 dia. I drill two shallow holes at 45 degree upward angles, an inch or so back from the tip and bed in two short plugs of eraser. Trim with a razor blade to get the compression you need. Best bedding trick I've learned yet.
 
Tumbleweed said:
Yup. Me too. I have an old jacket made with paper thin leather that I've been cutting up over the years for the same purpose. If I want to get fancy, I use some of that cylindrical white eraser that's about 3/16 dia. I drill two shallow holes at 45 degree upward angles, an inch or so back from the tip and bed in two short plugs of eraser. Trim with a razor blade to get the compression you need. Best bedding trick I've learned yet.
Click to expand...

The eraser trick sounds great.
Bruce
 
Ok Thanks guys.

Sporkman said:
Is the barrel free-floating (or at least supposed to be)? Might be a contact point that as the barrel warms up it is causing the deflection. Try the 180s on a cold barrel then the 150s after it has warmed up and see if the issue occurs again on the later shots.
Click to expand...

I shot some other rifles between groups and let it cool down

yodave said:
how is it with the 150's now? is your scope falling apart on the inside? fair bit of recoil and lower end scopes can get eaten up pretty fast
Click to expand...

Scope is fine. This same thing happened to me about a month ago.

Tumbleweed said:
Yup. Me too. I have an old jacket made with paper thin leather that I've been cutting up over the years for the same purpose. If I want to get fancy, I use some of that cylindrical white eraser that's about 3/16 dia. I drill two shallow holes at 45 degree upward angles, an inch or so back from the tip and bed in two short plugs of eraser. Trim with a razor blade to get the compression you need. Best bedding trick I've learned yet.
Click to expand...

I couldn't hassle you for a picture? I am having trouble visualizing the orientation.

I'll check the barrel channel right away and try the shim trick next time I am out.

Cheers
 
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