Dealing with Donuts

[Norm]

What's the best way to tackle donuts on thick walled wildcats?
I'm playing with a .30 cal wildcat and am getting large velocity swings due to tight necks in the area of the neck base.
I have outside neck turned but this has not helped.

The offending wildcat being formed with 155gn HBC's that did not cause an issue due to the seating depth. However when I started using 230gn Berger's I found a real problem.

[Steve N]

Norm K & M carbide turning mandrels have a cutter that removes that donut.

[Norm]

Steve,
Do you run them the same as the normal turning mandrel? ie expand first then turn or just expand part of the neck and then cut out the thick bit in the bottom?

I checked their site out and got this........... THIS ITEM IS NOT
CURRENTLY AVAILABLE

[Brad Y]

You can internal ream. I do this on my shehane no turn chambers and I use an intermediate size bushing to make the sizes as close as possible to being able to remove the whole donut. But I also only size half to 2/3rds of the neck and leave the bottom section unsized. Alan Fraser does this as well. He has the results in the bank to prove it works ok.

[Norm]

Thanks Brad,

I have sent Procal a note asking if they have any.

[Steve N]

Norm the K & M carbide mandrel just has flutes at the start so it trims out the thicker donut when you turn the case onto it instead of using the normal steel mandrel. Not much good if you can't get one though...
You will probably have to get a compatible trimmer like a Wilson to use a reamer.
Steve.

[ShaneG]

Try BRT in Brisbane
I bought the same K&M pilot cutters from them.
Donuts are not an issue I have but have the cutter style pilots anyway in case.

[williada]

Norm, I can't remember where I read it but a bloke said he was getting donuts with the 230 Berger when his free flight was less than .235" on the reamer. I'll think about that. If you need to ream those cases I can do it for you. David.

[Norm]

Norm, I can't remember where I read it but a bloke said he was getting donuts with the 230 Berger when his free flight was less than .235" on the reamer. I'll think about that. If you need to ream those cases I can do it for you. David.

Thanks David,
I'm actually thinking of making the free flight longer to avoid the donut area altogether with the 230gn Bullets. But will try working on the cases first. A .308" Forster inside case neck reamer arrived in the mail today, so will see how that goes.
I will catch up with you and have a chat.

[bartman007]

Norm, I find keeping the bearing surface of the projectile away from the neck shoulder junction the key. This will give you more case capacity, and more neck tension consistency.

It sounds like you need a longer free bore to accomodate these heavier/longer projectiles.

If you are using a standard 308 case to push these heavier projectiles like in FTR, I'd suggest the effort may not be worth it. As running so slow to manage case pressures won't be as beneficial as running lighter projectiles like the 185 juggernaughts. FWIW

Cheers.

[aaronraad]

Norm, the K&M recommendation is to use the Expand Iron tool and push it just short of the doughnut and then use the neck turning tool.

http://www.kmshooting.com/catalog/case-neck-expanding-tools/expand-iron_complete.html

I used the tool prior to fireforming (no-bullet method) in my 25/60SMc cases to check for doughnuts. I didn't find any doughnuts, but the cases were already supplied neck turned anyway and I just wanted to be sure-to-be-sure...and all that is St Patrick's Day today!

[Norm]

Mike its not a .308 case so case capacity is not an issue but yeah it does have a short throat which causes problems with very long bullets....................

Thanks for the link Aaron..............

I run the new Forster inside neck reamer into a few cases today and guess what. No more donuts!
Actually no more neck tension at all with my custom sizing die. So when one problem is solved, another arises.
The reamer removed all the brass out of the neck to .308" and a projectile can now slide into the case with my fingers.

I can see two ways to fix this. First is to reduce the amount of brass that I am removing from the outside of the neck. This will make the neck wall thicker and the sizer die will then provide enough tension to hold the bullet.
The other way is to make a custom bushing neck die so that I can vary the neck tension by changing bushings.

More fun ahead but I can see light at the end of the tunnel.