6BRA and Forster Die honing

[Mudflap621]

So gearing up to start my journey into the BRA. Im thinking of sending the die out to get honed as I’ve got a little time. I use expander mandrels currently and planned on doing the same with the BRA.

What measurements do I need to take to give Forster an accurate dimension to hone.

Also is specific projectile crucial to start with? I’ve got limited supply of hybrids and a bunch of hornady 105 HPBT, will be using Lapua brass as well. I was planning on fireforming with the hornady and see how results were but I’m still a month or so out on the completion of the build and have no previous load development.

 

[spife7980]

All your bullets are going to be .243 or so, within the thou at least. So dont worry about the specific bullet, its not that critical. More important for future proofing would be to not have it opened up more than the die could compensate for if you moved to thinner brass.

You use mandrels, in that case I would have the dies honed dimension be .001-.002 less than that the mandrel puts the brass at.
I dont have a 6bra but I do have a dasher and my loaded necks are .268" (.268 total-.243 bullet = .025 total neck material/2=.0125 thick per side). So my turning arbor mandrel leaves them .266 which is .002 below the loaded diameter giving me the generic .002 of "neck tension". Because you want the mandrel to actually have to work the brass a smidge to get consistent results on the inside I would have the die honed to .264" in my case.
Adjust for what your brass thickness actually is though. Usually br based lapua cases end up .267-.269 loaded round diameter.

I actually have my dasher die reamed to .265 and the resultant brass is .2655 when the brass was new and it now leaves it at .266 due to spring back (after 9 firings even with annealing every time) so when I run the mandrel through it there is barely any resistance and it works fine as well.

 

[marchboom]

Download the die honing form (that you will send with the die) and indicate what dimension you want them to hone the die to. Just that simple.

 

[Mudflap621]

Thanks guys I’ll look at Forster form and also take some measurements tonight.

 

[Mudflap621]

All your bullets are going to be .243 or so, within the thou at least. So dont worry about the specific bullet, its not that critical. More important for future proofing would be to not have it opened up more than the die could compensate for if you moved to thinner brass.

You use mandrels, in that case I would have the dies honed dimension be .001-.002 less than that the mandrel puts the brass at.
I dont have a 6bra but I do have a dasher and my loaded necks are .268" (.268 total-.243 bullet = .025 total neck material/2=.0125 thick per side). So my turning arbor mandrel leaves them .266 which is .002 below the loaded diameter giving me the generic .002 of "neck tension". Because you want the mandrel to actually have to work the brass a smidge to get consistent results on the inside I would have the die honed to .264" in my case.
Adjust for what your brass thickness actually is though. Usually br based lapua cases end up .267-.269 loaded round diameter.

I actually have my dasher die reamed to .265 and the resultant brass is .2655 when the brass was new and it now leaves it at .266 due to spring back (after 9 firings even with annealing every time) so when I run the mandrel through it there is barely any resistance and it works fine as well.

So here are my measurements spife, they mirror yours pretty well. On the Forster Form it says if not using an expander ball to take .002-.003' off of loaded round diameter but may require new dies for new or aged brass. Are they not assuming the use of an expander mandrel?

Should I resize a piece of brass to get an exact measurement of where it lands with the die before I move forward? All brass is brand new.

Another thing I noticed is that the seating stem doesn't seem to match up to well to the hornady 105 as the bullet shows.

 

[spife7980]

So here are my measurements spife, they mirror yours pretty well. On the Forster Form it says if not using an expander ball to take .002-.003' off of loaded round diameter but may require new dies for new or aged brass. Are they not assuming the use of an expander mandrel?

Should I resize a piece of brass to get an exact measurement of where it lands with the die before I move forward? All brass is brand new.

Another thing I noticed is that the seating stem doesn't seem to match up to well to the hornady 105 as the bullet shows.

If not using an expander take .002-.003 so that you end up with ~.002 inside neck dimension below bullet diameter and then minus the little bit of spring back. So yes, that’s a worst case scenario. You don’t want to take so much out of the die that it can no longer properly size down.
If you are expanding you can leave a bit more in the neck and go .003-.004 below loaded round diameter.

I wouldn’t worry about sizing the new brass. That neck isn’t gonna change diameter much if any. As brass gets fired many many times it generally gets thinner so that’s why they talk about the old or different brass.

And you can send in the stem with the die and they should lap it up but you can also just do that yourself.

 

[smoothy8500]

Another thing I noticed is that the seating stem doesn't seem to match up to well to the hornady 105 as the bullet shows.

That looks like excessive seating pressure is squishing the projectile.

 

[Mudflap621]

That looks like excessive seating pressure is squishing the projectile.

I was thinking kinda the same thing when seating it but I honestly only seated one bullet to take some measurements. This was Lapua brass and I ran my turning mandrel through it first as well. This morning I ran the turning mandrel through a few pieces of virgin brass and it seemed to have little to no resistance at all.

I also took the die apart the 105 hybrid definitely fits contours of the seating stem better but the hornady 105 bt didn't seem too bad.

I have noticed that with my Lapua 308 brass that on the first loading the seating pressure seemed to vary some so wonder if this will be the same.

 

[Mudflap621]

Im still a few weeks out on my barrel getting delivered so I cannot take any CBTO measurements I was just guessing when seating this and think I might have went a little deeper than I should have. COAL of that round was around 2.25 I believe.