A 7m/m bore dia would be a 222 gauge based on two methods of calculation both of which give same result:
UK Proof Formulae with lead having an s.g of 11,352 (gms/cm3)
and 1m/m= .03937"
Dia in Inches = 4.6578 divided by N ( Number of gauge)
Result 222
or long hand volume of sphere = 4/3 pi r3. r=3,5mm , r3= 179.573mm3, 11,532gms x .1796 = 2.039 gms, 1lb lead = 453.515gms. 453.5 divided by 2.039 = 222.
248 is not gauge number.
Good luck with your new gun, if it is 7X57R then it should be a nice, useable gun. Post back with photos of a hunt.
Regards Hugh Lomas
