Reaming Donuts...does it shorten brass life?

[ratbuster]

I shoot high volume varmints and my favorite cartridge is the 20 Vartarg. Unfortunately the neck turned Lapua brass I use develops donuts after the second or third loading. I prefer to use a Lee Collet Die (after a Redding body die) because I get less runout, more consistent neck tension and a a bit better accuracy than with a Redding bushing die (without neck expander) but the mandrel on the LCD will not pass through the donut unless I ream them.

When I ream the donut it recurs after another 2 shots or so. I am concerned that repeated reaming will significantly reduce the number of reloads I can get out of the brass. If so, I will use the bushing method as the bullet seating depth is far enough out that the donuts do not impinge on the bullet. If brass life is not reduced appreciably I will ream the necks and use the LCD to maintain that edge in accuracy the LCD provides.

Interestingly the donuts do not exist until after body sizing. I tested several hundred fresh fired cases last night using the mandrel of the LCD which slid into every neck without any resistance. This morning I sized about 40 cases with the Redding Body Die (.0005 to .001 shoulder bump) and the mandrel will not pass through any of the necks after the sizing.

SO...does inside neck reaming donuts affect brass life?

Thanks for your replies,

Phil

 

[BenPerfected]

What works for me is to run the perfect size K&M expander mandrel as a follow up step each time you full length size. If your necks are very consistent, you will also end up with low runout and consistent neck tension.
Ben

 

[alinwa]

I shoot high volume varmints and my favorite cartridge is the 20 Vartarg. Unfortunately the neck turned Lapua brass I use develops donuts after the second or third loading. I prefer to use a Lee Collet Die (after a Redding body die) because I get less runout, more consistent neck tension and a a bit better accuracy than with a Redding bushing die (without neck expander) but the mandrel on the LCD will not pass through the donut unless I ream them.

When I ream the donut it recurs after another 2 shots or so. I am concerned that repeated reaming will significantly reduce the number of reloads I can get out of the brass. If so, I will use the bushing method as the bullet seating depth is far enough out that the donuts do not impinge on the bullet. If brass life is not reduced appreciably I will ream the necks and use the LCD to maintain that edge in accuracy the LCD provides.

Interestingly the donuts do not exist until after body sizing. I tested several hundred fresh fired cases last night using the mandrel of the LCD which slid into every neck without any resistance. This morning I sized about 40 cases with the Redding Body Die (.0005 to .001 shoulder bump) and the mandrel will not pass through any of the necks after the sizing.

SO...does inside neck reaming donuts affect brass life?

Thanks for your replies,

Phil

YES reaming donuts decreases brass life......... But not for the reason(s) you seem to think.

Please read again the beginning of your paragraph 3

Interestingly the donuts do not exist until after body sizing. Phil

You might ask yerself......."WHY do the donuts not exist until after body sizing???"

And the answer is, "BECAUSE BODY SIZING PRODUCED THEM!!!!"

That's where donuts come from.

In other words, the donuts are an artifact of, a result of sizing.

period.

There is only ONE mechanism for producing donuts and that mechanism is the act of pushing the shoulder back so if you're getting donuts, you're sizing too much

 

[Richard Coody]

how often are you having to trim? good clue if shoulder brass is migrating into the neck.

fired brass will not show a donut. all imperfections are pushed to the outside. bushing neck sizing pushes the donut to the inside. expanders and mandrels push them to the outside.

to each his own but i believe the best method to handle donuts is to push them to the outside and turn them off cutting slightly into the shoulder.

make sure you are not bumping your shoulder back more than 1 or 2 thousands. if fired brass chambers easy it is not fully fireformed and shoulder bumping is not needed.

 

[CaptainMal]

Had a sizing die custom made to match the reamer of my new BRA. No expanding mandrel but I turned and varied the act insert size to get my neck tension. Couple firings and - donuts.

Sure I reamed them out once. Then thought about the whole thing and made a .2415 expanding mandrel for that decapping pin. No more donuts. Pushing works.

 

[searcher]

In my experience, the short answer is no.

 

[eas1949]

Only if you don't fully ream the lead donut!

 

[ratbuster]

YES reaming donuts decreases brass life......... But not for the reason(s) you seem to think.

Please read again the beginning of your paragraph 3



You might ask yerself......."WHY do the donuts not exist until after body sizing???"

And the answer is, "BECAUSE BODY SIZING PRODUCED THEM!!!!"

That's where donuts come from.

In other words, the donuts are an artifact of, a result of sizing.

period.

There is only ONE mechanism for producing donuts and that mechanism is the act of pushing the shoulder back so if you're getting donuts, you're sizing too much

Alinwa: I am not pushing the shoulder back too much. Bump is .0005 to .001".

I have a PMA expander mandrel made for neck turning. I will try that and report back.

 

[ratbuster]

how often are you having to trim? good clue if shoulder brass is migrating into the neck.

fired brass will not show a donut. all imperfections are pushed to the outside. bushing neck sizing pushes the donut to the inside. expanders and mandrels push them to the outside.

to each his own but i believe the best method to handle donuts is to push them to the outside and turn them off cutting slightly into the shoulder.

make sure you are not bumping your shoulder back more than 1 or 2 thousands. if fired brass chambers easy it is not fully fireformed and shoulder bumping is not needed.

Very little case growth. 6 firings and just getting to the trim point. The body only die creates the donut.

If I try to force the LCD mandrel past the donut it will collapse the case shoulder.

 

[Dusty Stevens]

you ever try to just use a FL bushing die on every firing?

 

[ratbuster]

Dusty,

I have used a Redding FL bushing die for several firings but as mentioned in my first post I get better concentricity, more consistent neck tension, lower SD's and better accuracy on paper with the Lee Collet die. I make these statements without reservation as I have done careful side by side testing of the bushing method vs. the LCD three different times. If the Lee was not better in every way I would use the bushing die as it's less steps but like most of us I will usually take the extra time to get the best accuracy. Having said that, if I am faced with too much reloading and too little time then out comes the bushing die.

I took Richard's advice and tried pushing the donuts out with my PMA expander. It worked well, allowing the LCD mandrel to pass inside the donut easily so I'm good to go.

Phil

 

[243winxb]

Partial neck sizing with collet die
Posted by on 13 August 2015 03:19 PM
If you want to resize just a part of the neck, find a washer at your local hardware store the has an inner diameter large enough to fit over the case, and an outer diameter large enough so that it contacts the collet sleeve that protrudes from the bottom of the die. Slide this washer over the case after the case has been inserted into the shell plate. Now when the ram is raised, you can still close the collet by applying force at the top of the stroke, but the case will not go up as far into the collet, and the neck will be sized less an amount equal to the thickness of the washer.

http://leeprecision.net/support/ind...iew/137/0/partial-neck-sizing-with-collet-die

 

[MagnumManiac]

Try a Forster FL die WITHOUT the bushing, dry lube your neck ID and see where you get using the expander.
Forster dies DO NOT expand the neck excessively like other brands, .0005”-0015” is max in my dies on the expander.

I do not get donuts. Period.

Cheers.

 

[alinwa]

Alinwa: I am not pushing the shoulder back too much. Bump is .0005 to .001".

I have a PMA expander mandrel made for neck turning. I will try that and report back.

I'm not arguing...... just stating that donuts ARE shoulder brass that's been pushed into the neck.


From sizing.


I load dozens of chamberings from 22BR to several huge 338's. I load cases dozens, even hundreds of times without donuts.


And rarely if ever trim.

 

[ratbuster]

Alinwa:

Do you use. Lee Collet Dies? If you don't you may have donuts and not even know it.

Bottom line is I am bumping the shoulder a bare minimum.

 

[alinwa]

Alinwa:

Do you use. Lee Collet Dies? If you don't you may have donuts and not even know it.

Bottom line is I am bumping the shoulder a bare minimum.

No, sorry. I don't use factory dies except on 4 bbls where I had the reamer made from factory dies....... like I had the die mailed directly to the reamer maker before even seeing/using it.

 

[foxguy]

No, sorry. I don't use factory dies except on 4 bbls where I had the reamer made from factory dies....... like I had the die mailed directly to the reamer maker before even seeing/using it.

Alinwa,

Can you tell us how you are sizing your Brass. Are you using a Bushing Die and bumping the shoulder back appx .001 and neck sizing for appx .001 neck tension or are you using a FL sizing die with its neck sized (ground/polished) to your desired dimension as determined by the brass , bullet used loaded neck dimension?

TIA

 

[alinwa]

Alinwa,

Can you tell us how you are sizing your Brass. Are you using a Bushing Die and bumping the shoulder back appx .001 and neck sizing for appx .001 neck tension or are you using a FL sizing die with its neck sized (ground/polished) to your desired dimension as determined by the brass , bullet used loaded neck dimension?

TIA

All of the above and several more. Of the custom FL sizing dies I use Neil Jones, Hornady Custom Shop, Borden, Harrell, Whidden, and my own. This is a large subject but, in short, the die MUST fit your specific chamber...... ie if you buy 6 identical rifles from a gunstore, you will need 6 individual sizing dies. In fact most often even if you have 6 identical chambers cut by the same reamer, by the same gunsmith, you will need several sizers as the chambers will vary enough to preclude mixing.

In addition case design enters the picture.

It is my opinion, based on extensive testing that it is impossible for some shapes to be maintained correctly. Examples are the 22-250AI or 243AI and even the 22-250 (for very different reasons.) Whereas the 6PPC and 6BR, 220 Beggs and others are designed for easy maintenance, exhibiting characteristics which, while they can be designed into nearly any case, often aren't.

 

[dcali]

It is my opinion, based on extensive testing that it is impossible for some shapes to be maintained correctly. Examples are the 22-250AI or 243AI and even the 22-250 (for very different reasons.) Whereas the 6PPC and 6BR, 220 Beggs and others are designed for easy maintenance, exhibiting characteristics which, while they can be designed into nearly any case, often aren't.

Care to expand on this? What are the characteristics you think lead to easy brass maintenance?

 

[ratbuster]

Alinwa...
Do you think if I have a custom die made by Harrell's using my 20 Vartarg brass the donut problem would not occur assuming I used new brass?