The "dreaded donut"

[Buck1970]

Thanks gentleman for this thread and your post.
Probably one of the more informative ones I've read on here in a while.
I've learned two new things, both of which make shooting safer.

 

[nicholasjohn]

Now that I think back, I did have a 243 that created donuts. Once rechambered to 243 AI that ended.

I've read that the 40 degree shoulders of the AI-type cartridges corrects the brass flow issue. I don't understand why this is so, or even IF this is so, but it sounds like that is what you've found. Lots of ins & outs in this handloading stuff ……..

 

[parshal]

I've experienced doughnuts in my 6 Creedmoor Hornady brass and the 6.5 Sherman Short with ADG, Bertram and Norma brass. Mandrels do not push the doughnut to the outside on either of these. The only way I've found to remove it is to cut it out by reaming the neck. Or, ignore it if the base of the bullet doesn't hit it. That depends on your seating depth and distance to lands so you may not be lucky enough to ignore it.

 

[wonderman4]

If the donut is allowed to stay in place, it will affect the characteristics of the cartridge by creating a restriction that will affect gas flow when fired. I will say that it may not be noticeable on target, but it is detrimental to consistency.

 

[IHFarmer07]

@wonderman4 is right, but it will show up on target beyond 500yrds because of the es and sd's are high.

I've been messing with donuts on two of my long range hunters/shooters. It depends on what your looking to do with your shooting, if your looking for the most consistency for shooting beyond 500yrds it is worth trying to get rid of them.....if your shooting less than 500 probably not worth it but it depends on the size of bullet and cartridge your using, because the donut will affect the es and sd's. In the end, depending on the range and cartridge you can miss high or low.

I've tried a bit of everything on those two guns of mine and the best is to find them using pin gages. Then I've found turning the necks with the proper degree cutter to the degree of you neck/shoulder is what will cure it, but be sure not to cut too deep.

I've tried Reamers and they work but, the neck has to be sized perfectly. I've tried using just the K and M neck turner mandrel as I turned the necks with what universal cutter they had and it didn't/don't work. There was still a trace of donut there. So the proper degree cutter is essential, found out the hard way! Do what I said in the paragraph up from this and go on with life.

 

[villagelightsmith]

Those dreaded donuts have shortened my arms until I can barely reach this computer keyboard!

 

[parshal]

I use pin gauges, too. I had to size the neck perfectly to then be able to use a chucking reamer to remove the doughnut. It was a lot of trial and error and a couple different reamers in .0005 increments to find the right combination.

 

[IHFarmer07]

I use pin gauges, too. I had to size the neck perfectly to then be able to use a chucking reamer to remove the doughnut. It was a lot of trial and error and a couple different reamers in .0005 increments to find the right combination.

Haha yep, been there done that!!! Like I said, EASIEST way I found was neck turning into the shoulder just barely touching the shoulder.

Otherwise @parshal's way will do the same just with more trial and error as I also found out, getting chucking reamers from Amazon and sending back what won't work yada yada.

 

[parshal]

I wish beck turning fixed it for me. The SS required neck turning to start and I still got the doughnut.

Maybe I'm just a bad reloader

 

[BountyHunter]

[ Then I've found turning the necks with the proper degree cutter to the degree of you neck/shoulder is what will cure it, but be sure not to cut too deep.

You hit the nail on the head, you have to have a cutter with the proper degrees to cut the correctly. Do that and ZERO donuts. I should have mentioned that earlier. IMO K&M turners are the best for that.

 

[IHFarmer07]

I wish beck turning fixed it for me. The SS required neck turning to start and I still got the doughnut.

Maybe I'm just a bad reloader

That sucks, what's your reloading process and with what dies?

Ah na, it just takes time, A LOT of research and trial and error is all.
I just started reloading a year ago or so with a PIA cartridge and I tell you what, in the end it kinda made me be more consistent and anal on what to look for and so on because I had to do a lot of trial and error, asking and research!! I even had a guy that shoots F-class want to help me and one thing that has been very important that helped me is that whatever you do to your brass in brass prep do it EVERY TIME!

 

[IHFarmer07]

You hit the nail on the head, you have to have a cutter with the proper degrees to cut the correctly. Do that and ZERO donuts. I should have mentioned that earlier. IMO K&M turners are the best for that.

Thanks, it wasn't too long ago when I finally realized that, that's what I needed, the proper degree and when I was going to order one, K and M was very close to releasing their carbide cutters in differing degrees so I waited for them. I got two for the two precision hunting/steel punching rifles and all is well with the prc and I haven't blown a neck off yet!!

 

[GLTaylor]

The main reason I went to 40° AI shoulders years ago was to largely eliminate case neck stretching. I rarely ever have to trim my 5 ackley cartridges. Others, yes. 35° and down have to be watched/trimmed.
For donuts, flat base bullets not much trouble cause they're usually above it. For long bullets, the donut makes seating more difficult and causes sometimes significant swings in pressure, SD and ES. Turning necks down to kiss the shoulder eliminates most. Wilson also makes an inside neck reamer that fits in their case length trimmer. Just remove the case trimmer cutter and insert the inside neck reamer. You can order their reamers to the ten thousandths diameter. Just had to remove donuts from my 25-284 cause i didn't do a good job on initial turning

 

[MNbogboy]

With my 6.5/257 Roberts Ackley (40°) formed from longer 270 & 06 brass, donuts were a problem.
I found that reaming fired un-sized brass first with a larger fractional reamer (17/64 ) by hand and then after sizing a .261 rcbs inside reamer in the redding "case lathe" cleared the donuts up in about 2 firings which included the initial fireform.
Took a while to figure it out, the sizing die pushed it in & the expander would push part of it back out.
With my "shorty" wildcat 7mm formed from shortened 6.5/284 brass. Outside turning and .281 inside turning after sizing they disappear after two firings also.