1941 Winchester .303

[Alan de Enfield]

An animated 'gif' produced some years ago by forum member Parashooter, showing why / how a sloppy head space COULD cause separations, particularly when combined with thin wall (SAAMI) cases.




Your headspace could be in spec at 70 thou, but using a thin rimmed case of (say) 58 thou means you have a 12 tho 'head clearance' allowing the case to stretch by 12 thou, and the weakest part (just above the web) goes 'pop'.

For me it is an excellent learning aid.