Seating Depth

T

Twud

Guest
I'm loading my first round of 20 rounds for a new 6BR. Using Lapua brass Berger bullets and Redding Comp Micro dies. Had to turn the necks on the brass to fit the tight necked chamber, I also chamfered and deburred the mouths, but that was all.
My problem is I can't get uniform seating depth. Measuring to the ogive I go from 2.794 to 2.798. The smith that built the gun says seat them .010" off the lands, to start.
Am I being too picky. I really want to produce the best possible ammo for this rifle.
 
Twud

For extreme accuracy work, consistant seating depth is a must. I would venture a guess that .004 spread is way too much.

Without knowing any more than what you have said, I would say that the seating die is the culprit. I use a Redding seater,and one thing I do is to be sure that the shell holder contacts the bottom of the die rather firmly so as to take all of the slack out, and to furnish a positive stop.

Also, your seating stem might be contacting the point of the bullet rather than the ogive. That is a sure killer for consistancy.

As for what you Smith said, I would go the opposite way. Start about five in, and work either way from there. But I suppose you will try several different depths to see exactly what your combo likes.........jackie
 
There has been - -

lots of discussion on this issue and some not very long ago. I would suggest you look in the archives here.
 
jackie schmidt said:
For extreme accuracy work, consistant seating depth is a must. I would venture a guess that .004 spread is way too much.

Without knowing any more than what you have said, I would say that the seating die is the culprit. I use a Redding seater,and one thing I do is to be sure that the shell holder contacts the bottom of the die rather firmly so as to take all of the slack out, and to furnish a positive stop.

Also, your seating stem might be contacting the point of the bullet rather than the ogive. That is a sure killer for consistancy.

As for what you Smith said, I would go the opposite way. Start about five in, and work either way from there. But I suppose you will try several different depths to see exactly what your combo likes.........jackie
Click to expand...

Jackie,
Are you using a Redding competition die? The model with the sleeve that slides in the die body? If so, are you lowering the die body so that it touches the shell holder? In other words the sleeve is completely encased in the die body when the ram is up.
I'm not sure why I set mine half way in but this could be the source of my troubles.
Mark
 
Twud

That is probably your problem. The Redding Seater is an excellent tool, but you have to let the shell holder seat firmly against the bottom of the die body in order to acxhieve consistant seating depths.

Just set it to where you feel a distinct pressure when the press handle breaks over center........jackie
 
And, unless your 'smith

jackie schmidt said:
That is probably your problem. The Redding Seater is an excellent tool, but you have to let the shell holder seat firmly against the bottom of the die body in order to acxhieve consistant seating depths.

Just set it to where you feel a distinct pressure when the press handle breaks over center........jackie
Click to expand...

already worked up a load and seating depth, there is NO WAY in little green apple he knows where to seat that bullet. Every bullet and every barrel has a different place it likes.. As Jackie said, start w/ a jam and work in or out from there. Just be sure your seater is working from somewher in the ogive and NOT the actual point
 
Twud;
The problem you describe can also be a function of case neck thickness variations. This results in neck tension variations. Are you sizing with a bushing die after the neck turning?? How much clearance per side between the chamber and a loaded round?? Is the load heavily compressed?? I think I would eliminate these issues and then take a hard look at the seater.

Mike Swartz
 
Seating

David - You are correct, I don't know what load is going to work, at least until I try. For now I'm going to follow my Gunsmiths lead. After he built mine he built a duplicate for himself, except for the stock. He's shooting in the low teens. He shot a 5" group at 800 yards off a bi-pod, so I gotta' put some credence in his advice.

Jackie - I have no doubt you've come up with the answer. Thanks!

Mike - 265 chamber, 263 loaded round, 261 empty round, Lapua brass

After break-in I shot one final 3 shot group out of a dry bore that measured
.216. Not bad, but I know it can do better. Federal primers, 32 grains of Varget, 68 Grain Hammonds flat base bullets
 
Just a side note--

For those not using specialized "B R" dies, if you set the die to contact the shell holder you may be crimping the case neck into the bullet. I know, I know, but check your die to make sure it doesn't have a crimping shoulder in it.

Hope I didn't crimp somebody's style?

Steve Moore
 
I suggest you sort those Berger bullets, and I believe you will find the problem.
 
Ron ...

Ron of Va said:
I suggest you sort those Berger bullets, and I believe you will find the problem.
Click to expand...

Sorting bullets only tells you that some bullets may have a longer shank or longer distance from base of bullet to ogive.

If the seating depth problem is eventually found and corrected, and you are now seating them all to say 2.794 inches, all you've done is seat some bullets deeper into the case neck because you are always measuring from the bottom or base of the case to the bullet ogive.

I used to sort non custom made bullets by shank length (base of bullet to ogive varied as much as .005") so that when I used them as part of a batch, I would know that the neck tension along equal length shanks, within the batch, was pretty much the same. Using custom made bullets helped reduce or eliminate that one variable. Custom made bullets I now use vary by about .001" or less. Art
 
Depth

I switched over to a Forster Competition Die that's very similar to the Redding. I'm now down to .0015" variance. I'm going to call that good enough.
Trying for optimal accuracy with these custom guns is a pain.
 
Twud ...

Twud said:
I'm loading my first round of 20 rounds for a new 6BR. Using Lapua brass Berger bullets and Redding Comp Micro dies. Had to turn the necks on the brass to fit the tight necked chamber, I also chamfered and deburred the mouths, but that was all.
My problem is I can't get uniform seating depth. Measuring to the ogive I go from 2.794 to 2.798. The smith that built the gun says seat them .010" off the lands, to start.
Am I being too picky. I really want to produce the best possible ammo for this rifle.
Click to expand...

I highly recommend reading this article from start to finish: http://www.6mmbr.com/catalog/item/1433308/977259.htm. This equipment ... and it sounds like you have some of it already ... will help you determine how far it is from the bottom of the case to the point where your bullet's ogive just touches the rifling. It's the easiest method I've found for finding my starting point. From my starting point, I proceed inward .005", .010" etc. Also, every time you measure with the O.A.L. tool, make sure the Modified Case is screwed on tight. It can tend to unscrew a bit as you remove the tool from your rifle's chamber. If the Modified Case is not fully seated on the O.A.L. Gauge, measurements will vary.

There are lots of methods that will tell you where you are ... for example a square or rectangle mark on the bullet ... that have been used very successfully, but I believe these tools will help you get started a little easier. The wooden dowel is really helpful in giving you a feel where the rifling is located. After you've mastered these steps, I believe jackie's suggestions on seating bullets will take you where you want to go. He's always helped me. Art
 
What I have found- -

abintx said:
Sorting bullets only tells you that some bullets may have a longer shank or longer distance from base of bullet to ogive.

If the seating depth problem is eventually found and corrected, and you are now seating them all to say 2.794 inches, all you've done is seat some bullets deeper into the case neck because you are always measuring from the bottom or base of the case to the bullet ogive.

I used to sort non custom made bullets by shank length (base of bullet to ogive varied as much as .005") so that when I used them as part of a batch, I would know that the neck tension along equal length shanks, within the batch, was pretty much the same. Using custom made bullets helped reduce or eliminate that one variable. Custom made bullets I now use vary by about .001" or less. Art
Click to expand...

is there seems to be a direct corelation between the length from the base of the bullet to where the ogive will touch the lands. In other words, if the bearing length varies, so does the length from where the seater stem touches the bullet to where the bullet's ogive touches the lands. I haven't figured out why but it sems to be that way.
 
Pete Wass said:
is there seems to be a direct corelation between the length from the base of the bullet to where the ogive will touch the lands. In other words, if the bearing length varies, so does the length from where the seater stem touches the bullet to where the bullet's ogive touches the lands. I haven't figured out why but it sems to be that way.
Click to expand...


hmmmmmmm,

So in the point up process there's a flexion going on which changes bearing length and ogive taper.......interesting. :cool:

al
 
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