Avoid the donut by necking down instead of up?

[NZVarminter]

Why is it that everyone seems to neck 243 Lapua brass up to 260 instead of necking 308 down?

If you neck up, you will create the donut out of the thicker shouder wall material, but if you necked 308 down, you not using any shoulder material?

Am I missing something?

 

[ShaneG.]

I necked 308 down for my 260ai. It was a better fit to my chamber.

 

[Lostcreek]

I use 308 lapua brass for my 260. I always neck down when possible for the reason NZVarminter mentioned.

 

[Elkbane]

NZ,
Because by necking down 308 brass, you'll have REALLY short necks. New Lapua brass measures from 2.013" to 2.015" long. When you neck it down, it gets a little longer, about 2.018". Nominal length of 260 remington is 2.035". With the short necks, you will eventually get a carbon ring in the throat of your chamber tha can be quite difficult to remove.

Now that Norma and Lapua make 260 brass, it's not much of an issue, but before that, getting decent qualty brass was a PITA for this caliber.....I tried necking down 308 Lapua brass and got short necks. Tried necking up 243 Lapua brass and got doughnuts on the third firing. Best I found before Lapua and Norma started making 260 Remington was 7mm-08 Norma necked down to 260......longer necks and no doughnuts..., but have since turned those cases back into 7mm-08. Had to turn the bottom of the necks to take off the shoulder material that had flowed into the necks while they were in 260 Rem configuration, but they are OK now.....

Elkbane

 

[NZVarminter]

ok, that makes sense

 

[brian427cobra]

I'm cheap so I neck down Win 7-08 to 260, turn the necks to .0135, uniform the pockets and deburr the flash holes from the inside, I FL everytime and it shoots great for the competitions I shoot in where I don't get my brass back, Lapua makes great brass, but for me its simply not worth double the price when Win 7-08 works so well.

 

[Lostcreek]

I have 1400 rounds through my 260 with lapua 308 brass and it is still as accurate as when it was new,no carbon problems at all. Yes the necks are shorter but with proper barrel cleaning it is a non issue.