Thread: Brass Bastards I know - 260 Nosler

Standard 6.5x284. Donut appeared on the first firing with both lapua and norma brass. Iv read a few theories but the only way I can see it happening is brass flow converging at the neck shoulder juction casing it to swell internally. Iv had it in a few cartridges but it seems more common with improved cases with 35-40 deg shoulder. Nosler brass in my 280ai was a consistent donut issue with with the first batch but a latter batch in the same chamber with the same dies etc was fine so Im guessing a slightly different composition in the brass resisted the flow maybe?
Sizing down necks is generally ok but when sizing up you are using the thicker brass from the shoulder to form the extra neck so will be a likely candidate for the bulge when sized if you dont turn them.