I'm guessing but Frankford Arsenal .30-06?
measurments are col83.80mm 3.301" cal 7.80mm 0.307" rim 11.86m 0.446" case is 63.27mm 2.491" long
Not got a book handy but the measurements look about right. I think the numbers are dates, so a Frankford .30-06 round dating August or March (is it an 8 or a 3?) 1919 possibly?
I'm by no means an expert, but I just had a quick squint in the Lee manual. Lists COAL as 3.340, cal as .308, and rim diameter as .473 for 30-06, so some of those sound a bit far out even allowing for variation in measuring, batch etc.?
Proportions look wrong for 7.62x51, would say that's it is a good chance as has been said it's 30-06 Springfield
Link here to a page that has almost identical markings to yours,as CSL says Frankford Arsenal
its f a 31. thats on the base and they are in a 5round clip my m8 dug up hundreds of them in a field along with some other stuff
Oh ok... probably 1931 vintage then
And just googling the clip looks like it's from a Model 1903 Springfield rifle
Springfield 1903 Stripper Clips | Military Surplus | MonsterMarketplace.com
Was the land once a US Military Base?
Chances are that they are for 1903 Springfield and the stripper clips aid with speed loading,M1 Garand has a totally different clip that holds 8 rounds.
The picture shows the clips if you click on the image
Bugger he types faster than me