Earlier when I posted photos of an “INERT” T13, I threw one in showing the T13 siting on a letter scale. I triple checked the weight and found it was 13.50 ounces (383 grams.) This particular inert was made during production at Picatinny Arsenal and is exact in every detail right down to simulated lead azide in the detonator cup (see photo.) Wikipedia says the T13 was initially 5.5 oz. but then increased to 12 oz. It also says everything about the T13 became classified. You be the judge here. But remember, the probability of a attaining a 13.5 oz. weight using sand filler and without a triple-beam balance scale is quite slim. Plainly put, 382.71 grams equals 13.5 oz. and my scale had to round-off to the nearest gram.