I've read an article on the doughnut effect this past week and it was the first time I have ever heard about it !

What I would like to know is how bad is it realy especially in calibres 303 and 375 H&H as I've also read that the 243 is one that is mostly affected by it ?

Will I really need to cut the outside and inside of the neck all I have been doing tha last couple of years is to trim them down to size ?

This is more of a problem with benchrest shooting where you are dealing with a tight chamber and reloading the brass many times 10 to 50 times. It will effect group sizes where you are concerned about 1/10" smaller group. Good Luck

Arguably, you want to maintain that doughnut in the .303 because that cartridge really stretches, both by design and by the actions it's normally chambered for. The doughnut can slow down stretching and inevitable head separation in the .303, so it's a good thing in that cartridge.

Actually the doughnut effect is quite nice, especially when used with the .243 Coffee...

I have found that cutting a doughnut is a waste of time, it is much better to just pick it up with your fingers...

What? Oh!

Never mind...

I generally get "the dreaded doughnut" after case forming operations. However, my .243Win. seems to delight in donut formation when I use light-to-moderate loads (1,750 fps) in it with cast bullets (87 grs.) When I use high powered loads in the same rifle, that rarely happens. To remove the donut I use a Forster reamer of the appropriate size (check their catalog) to return the inside of the neck to its "original" dimension.

Thanx all,

That article in the magazine made it sound bad enough to do something about it but as far as what you guys say I will just stick to sizing them to size only.

Another thing to remember is that the expander ball irons it out, if you use one. That's probably why it is only an issue on target rifles (bushing sized). FWIW, Dutch.

Am I the only one that's still looking for cops, and donut shops?

Hate to try to get over all the wise ass comments to answer a serious question from someone, but I'll try.

The donut is usually as the result of having a neck whose wall is thinner than the wall of the shoulder at the junction with the neck. This comes about as the result of neck turning. Another good reason not to turn necks. This can be as result of turning for a tight necked chamber in a bench gun, or for a wildcat cartridge where the neck is formed in the thicker body of a parent case. Typically most of your commonly used brass has a thickness approximately the same in the shoulder as the neck so that when that portion of the shoulder eventually folds into the neck when sizing, there is no effect since the walls are all the same thckness.

In a tight necked bench gun the necks could be thinned several thousandths under the thickness of the shoulder so that when the case stretches for any reason, the thicker shoulder starts folding into the base of the neck producing the donut.

The only times I've experienced the donut is when I haven't turned brass for a tight necked chamber properly. You need to cut into the shoulder a smidgeon without cutting too much, which will break off the neck. Too little and you'll get a donut eventually. I've also experienced it when forming Jamison cases out of 404 Jeffery. Necks of the Jamison are way into the body of the Jeffery and the necks have to be both turned and reamed. For hunting ammo in this cartridge you have to set the shoulder back slightly each time you size and eventually you'll get a donut at about 8 reloads. In normal use with standard unturned cases you may never see a donut, except at a donut shop.