Thread: . 284 Winchester

Originally Posted by cameronjackwhite

.318 neck eliminated the donut issue from necking up 6.5x284 I believe. Pretty sure @GWH knows more on the subject

Yes, a larger diameter neck may offer a possible work-around if you are prepared to arrange your sizing gear to partially size the necks. This has often been discussed on here but perhaps is not necessarily an easy concept to grasp, so I've added some diagrams below that might be helpful:



Above is the starting situation with a donut present.

One possibility is that the freebore may be sufficiently long to allow the bullet to be seated forward in the neck ahead of any possible interaction with the donut. This assumes that having the bullet seated right out is where you want it for jump/engagement with the rifling.

More commonly though - and this is particularly so for the longer VLD-style bullets - the cartridge-overall-length (CoL) has to be reduced because of the size of the rifle's magazine. Then the bullet has to be seated further down in the neck, perhaps with the boattail pushed down into the powder column. This is where the larger neck clearance may be helpful as shown in the second diagram with the bullet in this position.



It works in this way: on firing the neck is blown out to the available neck diameter, and with a larger diameter this will hopefully also be sufficient to expand the donut beyond the diameter of the bullet. By then only sizing back a % of the neck, the bullet may still be held, and the donut is left with the lower part of the neck - un-sized and clear of the bullet shank as shown.