Seating Depth

[George Foster]

If you are getting two shots and one out in a three shot groups should you seat the bullet longer or shorter?

I should have been more specific, this is a load I worked up a few months ago. I am talking a series of three shot groups not just one. I have shot groups as small as 3/16" and today for six three shot groups it averaged 9/16" for the six groups. It is just a Ruger MKII 243 sporter rifle, the groups all have two touching and one that is below. I know I seated this load at 2.630 instead of the 2.645 that I normally use for the rifle.

 

[Nimrod84]

George,

I'm not an expert, but when I have 2 in and 1 out, I try seating deeper first. It usually helps shrink the group down, but not always.

Since you appear to be seating deeper already and have worse accuracy, you might be in "the not always situation". "The not always situation", is when environmental changes force a load out of its preferred "node". Usually warm or cold weather will take a load right at the edge of a node and open it up. For me, in these situations, seating depth adjustments don't help as much as adjusting the powder charge to better match the new conditions.

Hope that helps.

 

[George Foster]

Nimrod84,

About four years ago I ran bullet seating depth tests on my rifles. My 243CDL gives the best groups at 2.630 and the Ruger seemed to shoot the best groups at 2.645. I have sometimes thought the Ruger gave me better groups at 2.625 and that is why I tried the 2.630 when I did the ladder test for this powder, bullet workup. I may well in the spring probably run another seating depth test with this rifle and this load. Or I may just test with the 2.625 seating depth and see what happens. I tend to feel you are correct about going shorter.

 

[wvbuckbuster]

Are you using the same bullet in each of your seating tests? Dan.

 

[jezzolo]

Bedding issue?

 

[George Foster]

Yes I use the same bullet, the powder has varied.

All my rifles are glass bedded and barrels free floated.

I think what I will do when I can is run a seating depth test each .0005 apart and see if I need a new seating depth for the rifle.

 

[jimbires]

if 2.645 shot the best a few months ago , I'd load some up at that length and see if they shoot good again . I'd see how these shoot before I went through a seating depth test again .

 

[George Foster]

That is what I will do, but I also want to do a seating test of .005 increments as I have always used.010. I would just like to see if I am missing anything.

 

[joelkdouglas]

I’ve always read/heard that 2 in 1 out means to seat deeper.


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[George Foster]

Thank You, I knew I knew at one time but couldn't remember now which way to go. If I remember correctly opposite seat longer?

 

[joelkdouglas]

I have read/heard if a triangular group to seat out.

Of course 5- or 7-shot groups (or more) make it tough to tell.


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[jimbires]

George , I've also read two and one means to seat deeper . I've never really paid enough attention to actually say that is correct . what I have done for a long time is start at the max length my rifle will allow . I'll either start at a very short jump to the rifling , or I'll start at max magazine length , whichever one is shortest . then I'll work my seating depth shorter . by starting at this max length I only have one way to go , this is shorter . it takes the guess work out of this process .

 

[George Foster]

I normally start .010 off the lands and load three rounds each .010 deeper and test. I am thinking about loading a series of every .005 and see. This is always after I find the best powder charge, I start 2-1/2gr below max and load three every 1/2gr up to max.