I dug up my OEM 2013 Subaru BRZ lugnuts and weighed them for you.
1 lugnut = 25 g (actual measurement)
5 lugnuts = 125 g (4.40925 oz., or 0.27558 lbs.) (actual measurement)
10 lugnuts = 250 g (actual measurement)
I weighed them on an accurate scale that measures in 1 g increments. I then measured 100 U.S. pennies as a reference check, and found it accurately measured 250 g, as it should. So, I think you can trust this measurement. Note that the lugnuts were not scrubbed clean and a 0.1 g scale would measure a bit of brake dust adhering to these dirty lugnuts. I hope this degree of accuracy is sufficient for your needs.
Stay safe.
And, thank you for your service.