Increase seating length for doughnuts

[6.5 forever]

Using Lapua brass fired 11x. I was punching primers on these today. I had a bullet on the bench and dropped it in the case and it stopped at the doughnut. I was quite surprised. I use Whidden dies and a mandrel.

So I loaded up 20 rounds in front of the doughnut at two different lengths (142 Sierra SMK). I will test these tomorrow.

Anyone else dealt with this?

 

[Rat Rifle]

Using Lapua brass fired 11x. I was punching primers on these today. I had a bullet on the bench and dropped it in the case and it stopped at the doughnut. I was quite surprised. I use Whidden dies and a mandrel.

So I loaded up 20 rounds in front of the doughnut at two different lengths (142 Sierra SMK). I will test these tomorrow.

Anyone else dealt with this?

Yes, brass flows in all cases. I just reamed donuts out of 6mm BR cases.

 

[6.5 forever]

Has anyone experience with accuracy changes when seating in front of a doughnut?

 

[gunsandgunsmithing]

Has anyone experience with accuracy changes when seating in front of a doughnut?

Oh yeah. Always stay in front of the donut. One exception that rarely gets discussed is having a neck diameter that is generous enough to allow the donut to form, yet not interfere with the bullet and olnly sizing the neck above the donut area. Works! And it allows you to seat below the donut with zero down side other than a nearly immeasureable affect on brass life without annealing. It just takes proper planning in reamer design and setting your dies. That's it!

 

[Ledd Slinger]

Yeah it’s best to seat bullets with the rear of the bearing surface in front of the donut area, but you should also be turning necks with a cutter that matches your shoulder angle. Cutting into the shoulder a small amount to make that part of the brass thinner as you turn necks helps prevent the build up of donuts as the brass flows forward during firing. See photo below.

If you don’t want to turn necks as described, then changing your seating depth is really the only option.

And yes your accuracy will probably change if your bullets were seated into the donut and now you seat the bullets farther forward. Changing seating depth for any reason, to avoid donuts or not, can definitely effect accuracy.

 

[Chris Edmondson]

11x with Lapua 6.5 Creedmoor unturned brass is about where I'd notice donuts as well. I suspect it starts a bit before I notice it, lets go with 10x, nice round number. Using any neck turning method to cut into the shoulder buys me enough reloadings to make it to where loose primer pockets make their appearance, that's when I retire the lot. Another approach I've taken once I notice donuts is to cull the herd, keep shooting the good ones until the remaining ones either have loose pockets or there's not enough of them to make it worth hanging on to them.

Sorry, meant to add a picture of some turned necks.

These were turned using a 21st Century 35° cutter, it really helps keep the donuts in check I've found.

 

[rebs]

when I drop the bullet in the case it hits the donut at 1.976, so how would accuracy be effected if I load to 1.977 or 1.978 ?

 

[Ledd Slinger]

when I drop the bullet in the case it hits the donut at 1.976, so how would accuracy be effected if I load to 1.977 or 1.98 ?

I would get a lot farther away from the donut than that

 

[rebs]

I would get a lot farther away from the donut than that

How far would you recommend ?

 

[Ledd Slinger]

How far would you recommend ?

Depends in the reamer and bullet. Where are you at for seating depth when touching the lands?

 

[rebs]

Depends in the reamer and bullet. Where are you at for seating depth when touching the lands?

1.988 is touching the lands

 

[Ledd Slinger]

1.988 is touching the lands

That’s where I’d start, then ladder test loads from touch to jams at .002” increments.

 

[rebs]

That’s where I’d start, then ladder test loads from touch to jams at .002” increments.

I did that and my best accuracy was at 1.976 but that is where the bullet hits the donut
Sorry I meant my jam is at 1.988

 

[Rat Rifle]

I did that and my best accuracy was at 1.976 but that is where the bullet hits the donut
Sorry I meant my jam is at 1.988

Sounds like Your load”likes” the donuts ?

 

[rebs]

Sounds like Your load”likes” the donuts ?

at 1.976 the bullet is just touching the donut

 

[Ledd Slinger]

I did that and my best accuracy was at 1.976 but that is where the bullet hits the donut
Sorry I meant my jam is at 1.988

If it shoots there with “consistent” accuracy, then might as well stick to what you got. If the donut gets bigger or creeps forward a touch, you might see some degradation, just have to watch it. I don’t like surprise losses of accuracy so I just stay away from the donut.

I usually design reamers around a specific bullet so the freebore allows lands touch to be where the bullet bearing surface is only about half way down the neck, give or take. That will always keep you out of the donut area with room to seat jammed, touch, or deeper in the neck.