What type dies to reduce/eliminate neck doughnut issue

[GSSP]

First post here. Took me long enough to actually get over here to do so. Any way!

Will soon take delivery of my new tact rifle in 6.5x47 Lapua. Surgeon 591 SA, Kreiger MTU 1:8.5, AICS, NF NXS 5.5-25x50, Shilen trigger.

I've never gone the bushing die route. Have always used either FL or Lee Neck Collet dies in conjunction with Redding body dies.

Am thinking about either Redding Type S bushing, Forster Neck Bump bushing or Forster custom honed FL dies.

I have been reading recently that the dreaded doughnut is not an "if" but a "when" issue. So, wanted to find out if the doughnut is a "when" issue and which set of dies will best handle the situation with the 6.5x47 L.

Thanks and have a nice day.

Alan

 

[AlNyhus]

Hi Alan.

My recommendation is the Redding type S f.l. bushing die. Donuts form for a lot of reasons, but I wouldn't get too concerned about it at this point. As you fire the cases, periodically check the inside of the neck of fired (but not resized) cases at the neck/shoulder junction and see what's happening down there.

A big cause of donuts can be simply pushing the shoulder back too much when sizing. Make sure you have a way to check this when you set up your f.l. die. The Hornady/Stoney Point headspace guage is a simple, inexspensive tool that allows you to check this important dimension.

The cause of 'the dreaded donut' can be dozens of things..sometimes peculiar to a particular chamber, die, etc, etc. setup...and sometimes several things contribute to this. And sometimes not. The bottom line with donuts is....it depends. Not very scientific, but that's been my observation.

Have fun with your rig..sounds nice. -Al

 

[savet06]

This is good info, Al. I was always under the impression that donuts came from necking up or down, but I didn't realize that it could (emphasize could) happen to a standard case. I guess it makes sense if you are doing excessive bumping or neck sizing that it might happen, but I didn't think it was much of an issue beyond that. It was also my understanding that as long as your bullet is not limited by the donut during seating it was more of a "leave well enough alone" situation. Meaning that inside neck reaming was more to make you feel better than any actual gain in accuracy.
Thanks,
Mike

 

[AlNyhus]

Mike, my experience has been that there's no hard and fast rules on donuts. Well...maybe a few.

If you're sizing the entire neck length, it's good to check periodically at the neck/shoulder junction to make sure that area is staying where you put it after you run it through the bushing. If there's a donut inside the neck at this point, the extra thickness can be enough to push the o.d. of the neck at the n/s area 'out' after it's reduced by the bushing...making the o.d. clearance less. A slick way to check this is to get a neck bushing .001 over what the neck measures with a bullet seated....use it as a go/no-go guage.

Some people get rid of 'em as they form and some don't worry about it. People win with both approaches, within reason. ;D

There's just so much involved with this whole area and it's really specific to each set up.

I'd rather my doughnuts be the chocolate frosted type....with coconut. -Al

 

[mikecr]

Donuts are not a mystery. And they don't just 'happen' in the abstract.

Brass tapers in thickness from thinnest at the mouths to thickest near the webs. So unless turned out, brass WILL be thicker at the lowest part of the neck. This is a reason for the normal taper in chamber necks.
Your bullet bearing should never be seated so deep to cause an issue here anyway.

Now, donuts can be expected 'grow' when forming new neck area from thicker shoulder brass. This is common with wildcat forming.
They also grow over numerous reloads with high taper brass that has to undergo continuous trimming for proper length. In this case, the brass is being re-formed on firing -in the forward direction(putting shoulder brass into new neck area).

Based on the cartridge drawing:
http://www.6mmbr.com/gunweek072.html
The 6.5x47 does have a bit more taper than needed IMO, and I notice that Kiff reamers utilize coaxial chamber necks(non-tapered). People are pushing heavier/longer bullets than this case capacity supports well, so maybe they aren't throating long enough to get the bullets out of the neck/shoulder junction. Maybe they are running irrational pressures to get those bullets at acceptable velocities.
These factors might lead to the notion that donuts will be an issue.
But I run a 6xc, and donuts are not an issue with it.

Anyway, dies don't 'fix' donuts, anymore than they create them.
If there is sufficient clearance in your chamber neck, you can partial neck size. Or, you can turn, or ream the 'problem' away(if it is actually a problem).
But turning won't help long if the case grows in length to the point of retrimming.
You can take the growth causing taper out of the case through rechambering with a better design, or to stop seating bullets too deep. This might require extending the throat or going with a bigger magazine.

You might recognize here that these things a better handled through pre-planning, than afterthoughts and folklore.