12/24 or 300/600?

[Brookers]

Does anyone know what unit of measurement is used in the firearms act for the minimum barrel length/overall length.
I'm building a shorty at the moment and while I intend to make sure it is definitely long enough I was wondering what the act actually says. I have looked around a bit but couldn't see it.

Cheers

Brookers

[ovenpaa]

My FEO assured me it is 300/600 these days however I would work to inches, 12" is 304,8mm so another 5,0mm is nether here not there. Also do remember the barrel length is bolt face to muzzle and I have a 5,0mm brass rod that is marked at 12" and a bit more just to confirm to myself I am on the legal side.

[Brookers]

Thanks for that. I will work to 24" to be on the safe side then. Barrel will be about 16" as it's a Bullpup so I just need to keep an the overall length.

Cheers

Brookers