Donut fix

[Frankm]

So we ve been getting donuts on our tight neck chambering after we turn brass and fire first time. Running .0015-.002 clearance.

Is having to size and mandrel expand and do a second neck turning after the first firing “the solution”….? What are you guys doing and what’s working for you?
Thx!

 

[Bill Norris]

So we ve been getting donuts on our tight neck chambering after we turn brass and fire first time. Running .0015-.002 clearance.

Is having to size and mandrel expand and do a second neck turning after the first firing “the solution”….? What are you guys doing and what’s working for you?
Thx!

Although from what I've read, it's not a favorite thing to do some are running an inside cutter mandrel in the necks to remove the donut.

 

[mikecr]

What I do is neck turn slightly into neck-shoulder junction of new necks, so when that area becomes part of the neck on fire forming, it's not thicker (a donut). But I don't know what you're forming from what.

 

[Frankm]

Bill, thx for inside neck reaming thought. Candidly we ve been trying to stay away from that.
Mike most of the tight neck stuff , other than 22-250AI, is just trying to get necks thinned down for tight neck reamer builds. 22 GT from 6 GT, 6-280 AI from 280 AI, etc. We ve been cutting very slightly into shoulder but maybe we should take another .002 or so.

 

[Bill Norris]

Bill, thx for inside neck reaming thought. Candidly we ve been trying to stay away from that.
Mike most of the tight neck stuff , other than 22-250AI, is just trying to get necks thinned down for tight neck reamer builds. 22 GT from 6 GT, 6-280 AI from 280 AI, etc. We ve been cutting very slightly into shoulder but maybe we should take another .002 or so.

Yea, I try to stay away from it as well. I normally as Mike stated, will turn into the shoulder on my 30BR brass a tad to try and avoid the dreaded donut. But it's easy to go too far if you are not real careful. My chamber neck diameter is @ .330 and my loaded neck diameter is @ .3275.

 

[std7mag]

Ok,
Am i the only one hoping for a thread on Krispy Kreme's?

 

[One Eye Pete]

I try to avoid donuts at all cost but when I do get them I use a K&M carbide cutting pilot to remove them.
Don't use it as a turning mandrel only to remove existing donuts.
I use it in the 21st century lathe with a small drill to provide the power (you need an adapter from 21st century to use K&M pilots in their neck turner). I did not have success cutting out the donuts when I tried turning by hand.
The fit of the neck over the cutting pilot is important. You don't want it tight, just to the point where there is no perceptible play.
Stay under 500 rpm and I also use plenty of fairly thick lube (STP added to oil) to help keep from scratching the inside of the necks.

 

[mikecr]

The problem with reaming is that it's cutter is a fixed diameter. So for any precision with it, you would have to somehow FL size necks to perfect diameter, after spring back, with a fixed diameter of downsizing.
It's just easy to be all wrong for the need.
It's a similar issue with trying to turn necks after fire formed.

You might try removing expansion all together, and of course avoid seating bearing into your donut thickness.

 

[Fuj]

In the wild catting trade, donuts are a way of life.. After fire
forming, I pick an ID reamer that just slips into the mouth
of the neck. I then run it in and make my cut. In a lot of cases
I don' even bother with cutting if my bullet seats way above it.
I however will need to cut, but not for bullet seating purposes
but for clearance for the the trimming mandrel.

 

[PopCharlie]

I have a a 6br with a .266 neck. To avoid doughnut, I just drive by the Krispy Kreme store and don't stop.....but seriously folks.... I blend into the neck/shoulder junction when turning. I also set up my F/L sizing die so the bushing leaves a small amount of the neck unsized, just above the neck/shoulder junction. I don't seat bullets into that area. I also use a Porter die and pin guages for the final neck sizing. This helps too.

PopCharlie

 

[Bill Norris]

I have a a 6br with a .266 neck. To avoid doughnut, I just drive by the Krispy Kreme store and don't stop.....but seriously folks.... I blend into the neck/shoulder junction when turning. I also set up my F/L sizing die so the bushing leaves a small amount of the neck unsized, just above the neck/shoulder junction. I don't seat bullets into that area. I also use a Porter die and pin guages for the final neck sizing. This helps too.

PopCharlie

I like to leave @ .050 to .080 at the base of the neck un-sized as well and try to avoid seating down in that area.

 

[NorCalMikie]

Push the donut to the outside then if you're turning, turn it off.
"OR" see if your bullets will seat ABOVE the donut. If so, load and shoot.
What donut? Don't see no stinkin donuts. Don't NEED no stinkin donuts!!

 

[PopCharlie]

I like to leave @ .050 to .080 at the base of the neck un-sized as well and try to avoid seating down in that area.

Bill,
I never measured it before now. Mine is .060...+/- a little.

PopCharlie

 

[Bill Norris]

Bill,
I never measured it before now. Mine is .060...+/- a little.

PopCharlie

Yea, mine will vary according to the bullet and how deep I want to seat it.

 

[NorCalMikie]

If formed (donuts) , usually just above or at the shoulder/neck junction. Lighter bullets will usually seat just above that point so no real issues.

 

[mike a]

Seat above the donut and you won’t know it’s there.

 

[AlNyhus]

Frankm: I push the shoulder back .015-.020 and then do a slight blend cut into the shoulder before firing the cases the first time. A faced off shell holder works great to push the shoulder back. A little oil like 3 In 1 lightly on the cases helps out for the first firing.

On fired cases, a chucking reamer that's a few thou. under what the inside of a fired neck measures takes care of them nicely.

Hope this helps. -Al

 

[Frankm]

Thx Al and all for good advice. We built a .002 undersized ‘spud’ for the lathe to push the donut to the outside. We then re-cut, second time, the outside of the neck. This was all on once fired brass.
Appears to have eliminated donut so we ll see what happens in next couple firings. ( we did turn into the shoulder at a 35 degree angle to hopefully help discourage any more formations). 22 GT, tight neck cartridge.