Neck tension ???? pics added

[mason]

I have been having some trouble with my new 6BRs grouping it seems to shoot 3 shots in one little hole then it might through one high or low. Once and a while it seems to shoot them all in one hole but most the time there's one or two out of the group..
The gun is a trued Remington 700 Mcgowen 10 twist barrel lee six stock bedded and a leupold 36 BRD scope all smith work done by Bob Green this gun is as good as any other bench gun i have ever handled its as solid as a rock...The only thing i can point out is i turned the brass myself and i can tell that some bullets seat way easier or tighter then the others..its a 268 chamber i shoot the 80 Moore bullets in front of n140 or Varget.let me know what you guys think ill post some pic of the poor-poor groups its been shooting ..And yes all groups shot over Gram wind flags..all groups shot at 100 yards.



***,#1)THREE IN MIDDLE HOLE ONE HIGH & ONE LOW***
***,#2)THREE UP TOP TWO LOW***
***,#3)FOUR UP TOP ONE LOW***
ITS DRIVING ME NUTS THAT I CANT FIGURE THIS OUT !!!!!!!!!!!

 

[TonyR]

I have experienced the uneven seating pressure as well with all of my guns including the 6BR. I found that my best ES and vertical dispersion happens when the seating pressure is fairly close measured with the K&M arbor press. It doesn't seem to matter as much what the pressure is as long as they are all close. I ended up doing three things to even it out:

1) Annealing the necks every other firing which maybe overkill but it doesn't seem to hurt things

2) Lubricating the inside of the necks with Imperial Dry Neck Lube before I put the powder in the case, particularly after I have used the ultrasound to clean the cases. I think that the inside of the necks get too clean and there is no carbon left to act as a lubricant.

3) Uniforming the inside diameter of the necks with an expansion mandrel after I have resized them. I have no idea why this is needed because my loaded neck diameters are very uniform and I use custom full length resizing die but it does work. Maybe I am lubricating the necks unevenly when I resize them.

Good luck.

 

[robbor]

Some one else mentioned a while back that they polish out the inside of the necks with flitz and it reduced scoring on the bullet and evened up seating pressure as well as slightly reducing it. might be worth a try.

 

[TheSilverFox]

What is the ideal twist rate for the 6br at 100 yards?
Some of those groups look like some I've had at HVLV 100/200 yard benchrest matches. LOL

I've had my br for 4 years now and I have tried a bunch of different reloading practices and found that extreme detail has not made that much difference. So for a while now I have been sticking to the basics.

Full lenght resizing to .0005' shoulder bump
.002' neck tension.
never dull necks
brush inside necks
clean primer pockets
jump bullet a little bit.
Clean every 15 to 20 rounds. JB bore paste, bronze brush, etc..
This all leads to less than 1' at 300 yards,with flags). This is not a bench gun though.

I also, on occasion, find uneven seating,feel) pressures on the arbour press,no turn neck 270) but I can't conclude that it decreases accuracy that much.I wouldn't focus too much on that If I were you.Unless you turn necks unevenly. What kind of turner do you use? Do you measure the thickness? Is it even from brass to brass and from top to bottom? Do you turn by hand or with a drill? I tried lubing necks for a while when seating bullet but didn't make much difference. I shoot a 1 in 7'tiwst with 105 MK and found that on occasion my 300 yard groups are smaller than the 100 yard groups, go figure. Bullet stabilisation thing. Have you tried other bullets, maybe you have a batch your rifle does not like? Is your scope tight?

 

[mason]

Thanks to the short range guys i got it together......
A little here a little there, now all the shots seem to find the same hole...Thanks guys.
some more tergets to look at. Note the bottom left target was shot by my 5 year old son ..

 

[queen_stick]

Mason:

What exactly did you do to get the 'fliers' out of there? Was it the neck tension?

thanks,

Walt