Doughnuts

[jimsplce]

I know there has been a lot mentioned of Doughnuts. I understand what they are and where they come from generally.
What I don't understand and have not seen explained is the best way to deal with them when necking a cartridge up, specifically for the 30 BR.

After expanding the neck, I find that I have a doughnut. Should I remove it before neck turning and if so the best way to do it.
I can neck turn and get decent results with the doughnut still there. Or, I can use a neck turner pilot with a cutter to remove the doughnut and get decent results that way too. Which is better?

I often see a reference to using a reamer. Is that reamer being mentioned usually just a pilot with a cutter or is it better to use a reamer such as found in a machine shop.
If the reamer, as found in a machine shop is used, is it just trial and error and ground to the 10 thousandth?
I assume the neck would be turned AFTER the reamer is used. Is that correct.

For those who know.
When necking up for a 30 BR, is it better to do it in one step or two, such as using a 7 mm mandrel followed by the 30 mandrel?

 

[rsmithsr]

your bullet in a 30 br will never be anywhere near the dougnut...do not worry

 

[C.L. Peterson]

I know there has been a lot mentioned of Doughnuts. I understand what they are and where they come from generally.
What I don't understand and have not seen explained is the best way to deal with them when necking a cartridge up, specifically for the 30 BR.

After expanding the neck, I find that I have a doughnut. Should I remove it before neck turning and if so the best way to do it.
I can neck turn and get decent results with the doughnut still there. Or, I can use a neck turner pilot with a cutter to remove the doughnut and get decent results that way too. Which is better?

I often see a reference to using a reamer. Is that reamer being mentioned usually just a pilot with a cutter or is it better to use a reamer such as found in a machine shop.
If the reamer, as found in a machine shop is used, is it just trial and error and ground to the 10 thousandth?
I assume the neck would be turned AFTER the reamer is used. Is that correct.

For those who know.
When necking up for a 30 BR, is it better to do it in one step or two, such as using a 7 mm mandrel followed by the 30 mandrel?

Accurate Shooter has a discussion about the 30 BR and your questions will be answered there. The discussion is on their home page on the left side.
This discussion is by top 30 BR shooters-good info.
Good Luck
CLP

 

[Al Nyhus]

I know there has been a lot mentioned of Doughnuts. I understand what they are and where they come from generally.
What I don't understand and have not seen explained is the best way to deal with them when necking a cartridge up, specifically for the 30 BR.

After expanding the neck, I find that I have a doughnut. Should I remove it before neck turning and if so the best way to do it.
I can neck turn and get decent results with the doughnut still there. Or, I can use a neck turner pilot with a cutter to remove the doughnut and get decent results that way too. Which is better?

I often see a reference to using a reamer. Is that reamer being mentioned usually just a pilot with a cutter or is it better to use a reamer such as found in a machine shop.
If the reamer, as found in a machine shop is used, is it just trial and error and ground to the 10 thousandth?
I assume the neck would be turned AFTER the reamer is used. Is that correct.

For those who know.
When necking up for a 30 BR, is it better to do it in one step or two, such as using a 7 mm mandrel followed by the 30 mandrel?

Jim, I feel it's important to address the internal donut on the 30BR cases prior to neck turning.

Not everyone does this and having done it both ways, I have to say I've never seen any 'on target' differences.

If you're going to do this with an inside reamer/cutter, it's imperative that your case necks be as straight as possible relative to the case body before getting in there with a reamer. I mention this because I recently changed my method of expanding up and the necks were not as straight as with my previous method......gave me more than a little gas.

K&M makes a turning mandrel that has a cutter on the end to address the donut.

For what it's worth, here's what 100 30BR cases worth of donut material looks like after being removed. As you can see, the external 'lump' remains and is turned off in a seperate step before neck turning.

Good shootin' -Al

 

[jimsplce]

Jim, I feel it's important to address the internal donut on the 30BR cases prior to neck turning.

Not everyone does this and having done it both ways, I have to say I've never seen any 'on target' differences.

If you're going to do this with an inside reamer/cutter, it's imperative that your case necks be as straight as possible relative to the case body before getting in there with a reamer. I mention this because I recently changed my method of expanding up and the necks were not as straight as with my previous method......gave me more than a little gas.

K&M makes a turning mandrel that has a cutter on the end to address the donut.

For what it's worth, here's what 100 30BR cases worth of donut material looks like after being removed. As you can see, the external 'lump' remains and is turned off in a seperate step before neck turning.

Good shootin' -Al

Two questions:

You say, "the external 'lump' remains and is turned off in a separate step before neck turning."
Are you saying the external lump is turned off in one pass and then followed by a second to-size finished cut?

My intention is to turn the necks in two passes, using two different K&M cutting tools. The first cutting after expanding, will be done with a pilot with a cutter. The second and finish cut will be done with a non-cutting pilot.

Do you have an opinion on using two expanding mandrels, specifically a 7mm followed by a 30 cal.

 

[Al Nyhus]

Two questions:

You say, "the external 'lump' remains and is turned off in a separate step before neck turning."
Are you saying the external lump is turned off in one pass and then followed by a second to-size finished cut?

Jim, that's how I do it. I know others that turn the external lump off when the neck is turned, too. It depends a lot on your cutter setup.

My intention is to turn the necks in two passes, using two different K&M cutting tools. The first cutting after expanding, will be done with a pilot with a cutter. The second and finish cut will be done with a non-cutting pilot.

That's certainly a good approach. For reference, check the diameter of the two pilots with a good .0001 micrometer.

Do you have an opinion on using two expanding mandrels, specifically a 7mm followed by a 30 cal.

I've always done a single expand up with a tapered 6-30 expander with no issues on many hundreds of 30BR cases over the years...until the other day when my 'new and improved' expander gave me some issues, that is.

Others I know expand up in multiple steps and have good luck. A good way to check things is to take a few sacrificial cases, expand them up and do a cut to remove the external lump. If the blend from the cutter into the shoulder is real wavy, either the case necks aren't straight to the body and/or the case neck may be too loose on the mandrel causing it to 'cock' as it starts cutting the heavy external lump. With a good fitting mandrel and doing them by hand, you should be able to feel the case get looser on the mandrel as the external lump is cut away. If you get in the case necks with some pin gauges, you can measure the difference of the internal donut before and after the external lump is cut away.

And it's important to not over think this whole process, either. I used to blissfully neck up, turn and shoot. Then I started measuring more stuff. Sometimes, the deeper we dig into stuff, the less we learn.

For example, this stuff came out of the inside of the new Lapua 6BR brass I necked up and cut the donuts out of. It's mildly magnetic and is most certainly not brass. There was lots of individual ribbons of this stuff but this is some that hung together. Sometimes it better not to go looking....

Good shootin' -Al

 

[Butch Lambert]

Fireform without a bullet and before turning the necks.

 

[Al Nyhus]

Fireform without a bullet and before turning the necks.

Butch, that way certainly offers a lot of advantages.

For those that haven't considered doing it that way, maybe you could explain your process for the 30BR? That way, they can have some options and decide.

Good shootin' -Al

 

[jimsplce]

Fire forming without a bullet is certainly one way to do it and is probably a good one. I have a fire forming barrel for my 6PPC.

There are two problems with fire forming for the 30 BR newcomers like me. I don't have an extra old barrel, and if I did, I'd have to pay someone to chamber it properly as a fire forming barrel.

The likely hood of finding a take-off barrel that fits my action is highly unlikely in 30BR. Take-offs in the 30BR are not as plentiful as old PPC barrels. I assume there are some, but 30BR's take a long time to wear out. And, I really don't want to fire form without a bullet in a brand new barrel. I don't know why, but it seems wrong.

A novice's thought.

 

[Pete Wass]

What I did once

was to fire some with 6MM bullets in them and the cases came out great. I think I remember there being no lump after but it was many years ago. I haven't made any 30 BR cases in over 10 years. Years ago I got to thinking that if one full length re-sizes their cases, they end up with what the full length die gives them so if that be true, cases become universal, providing the neck thickness is similar. There is no getting around the Full Length sizing die, is there? So, dedicated cases are a moot point.

Pete

 

[Butch Lambert]

Jackie Schmidt uses 6mm bullets in his 30BR for fireforming. I used a worn out 22 barrel to do my 30br fire forming barrel. Drill and ream the bore to accept the 30br reamer. Check your reamer specs for your overall length. Trim as needed. I use a stiff load of Bullseye capped with a wax or playdough plug. Fire them and then deprime. Check OA length as the normally lengthen. Trim to your desired OA length. It takes very very little to expand and turn.