No donuts 284 forming

[86alaskan]

OK, my 25-06 reforming has been going well, now onto the freshly built 284 Win. I am using lapua 6.5-284 brass and I have the sinclair expanding die to neck up to 284/7mm. Now, I keep reading about the dreaded donut that comes from expanding up. What can I do to avoid this problem. My chamber is the CBI 284 Win match throated for 175 sierras. I will be using a redding type s full length bushing die for my sizing needs, .309/.310 bushings. It's a no turn neck chamber, so if at all possible I don't want to have to turn, but just in case I have a turning mandrel ready to go. thanks

 

[dbramley]

Have to turn the necks, all the way into the shoulder.

 

[Laurie]

That eases things, but often doesn't offer a complete cure. The usual (and best) remedy is to ignore / circumvent the likely formation of the doughnut by using a throat / bullet combination that sees the bottom of the bullet shank seated above the affected bit of the case.

Alternatively, as applies to my 284, it's an inside neck-reaming job. Since I use the Sinclair / Wilson trimmer, I have Wilson's inside neck reamers for 6.5 and 7mm as I sometimes also see this issue with the smaller calibre too. The standard off the shelf size works for me, but one downside is that they're dimensioned for fired cases, so the first firing has to have the doughnut in place. So - you simply make sure the brass is used in practice, load development, minor matches and so on.

 

[nhm16]

My reamer has a 0.188" free bore so a 180 Hybrid will definitely hit the neck/shoulder junction.

I use an expander to neck up, then neck turn using a neck turner with a 40 degree cutter to turn all the way to the shoulder (and actually "biting" the shoulder a little bit).

Also remember that most bushing neck sizers don't/can't size all the way down to the neck/shoulder junction, so the effect of any donut that re-forms due to brass movement is greatly mitigated because that portion of the neck will not touch the bullet.

 

[fguffey]

Someone should ask about the 'dreaded donut', where does it come from and what causes it? I create donuts when forming, I have never formed a donut by necking up and or down.

When necking up the shoulder/neck juncture becomes part of the neck.

F. Guffey

 

[effendude]

Someone should ask about the 'dreaded donut', where does it come from and what causes it? I create donuts when forming, I have never formed a donut by necking up and or down.

When necking up the shoulder/neck juncture becomes part of the neck.

F. Guffey

That is where the donut comes from. The shoulder brass is thicker than the neck brass. When you neck up, part of the thicker shoulder brass becomes neck. When you resize the case, the brass is squeezed inside to form the donut at the bottom of the neck.
Scott

 

[fguffey]

When you resize the case

'When I?', not fair, when I neck up a case the neck gets shorter, I have no ideal what happens when 'you' neck a case up.

When forming cases I have had the neck completely close off the neck, that is a serious donut. I have cases that have been fired multiple times without ever forming a donut, I have other cases for different chambers that I expect donuts to form. I believe there is something about brass flow that reloaders do not understand.

I also believe donuts are formed through reloaders bad habits.

F. Guffey

 

[86alaskan]

ok good stuff, I've read that you can run the brass through a standard FL die after expanding and that's supposed to help. I'd rather not thin the necks more than absolutely necessary, so would I just adjust the cutter so it barely touches on the neck but then bites the top of the shoulder?

 

[nhm16]

ok good stuff, I've read that you can run the brass through a standard FL die after expanding and that's supposed to help. I'd rather not thin the necks more than absolutely necessary, so would I just adjust the cutter so it barely touches on the neck but then bites the top of the shoulder?

Yes. I don't do a full cleanup of the necks but the cutter will still remove a distinct and complete ring of brass around the neck shoulder junction (that's the donut being removed).

I also believe donuts are formed through reloaders bad habits.

Like others have alluded to, this donut is a result of the shoulder being thicker than the neck on Lapua (and Norma) brass. That's the same reason why Robert Whitley recommends you not use Lapua/Norma .243 Win. brass when forming his 6mm Super LR wildcat, and use Winchester or similar brass instead.

 

[86alaskan]

anyone able to post or link a picture of the right amount to remove from the shoulder? I'd rather not experiment on brand new lapua brass.

 

[fguffey]

Like others have alluded to, this donut is a result of the shoulder being thicker than the neck on Lapua (and Norma) brass. That's the same reason why Robert Whitley recommends you not use Lapua/Norma .243 Win. brass when forming his 6mm Super LR wildcat, and use Winchester or similar brass instead.

Could be talking apples and oranges. the OP is asking about necking up and someone has necking up confused with case forming, again, I form cases that cause a donut that closed the neck off, when that happens I am not necking up and or down I am doing serious case forming.

F. Guffey

 

[turbo54]

My experience based on using Lapua brass in a short action 284:

Load and shoot the virgin brass. The donut seems to appear after/during the first or second firing (usually the first).

Resize in a non-bushing FLS die (mine is a Forster). Be sure to get nice a consistent datum length on the sized cases.

Trim all the cases to a consistent length. This is important because it affects how deep the cutter goes in the next step.

Light neck turn AND inside ream using a K&M neck turning tool with cutter pilot.

Se the stop on the cutter pilot so the neck turning cutter cuts lightly into the shoulder.