I started with turkeys last year with some eggs I hatched - we got 3 stags, they were norfolk black x bronze so not as large as the BB breeds, but they finished in at around 14.5 lbs dressed weight, which was all we needed as there are only 3 of us!! I don't think you can kill them too young - if you only want a small bird then no point waiting till it is a 40lb whopper!, just make sure they are not mid moult as they are a pain to pluck then!
I shoot mine at point blank with an air rifle at the back of the head, as slitting their throat without either stunning/killing or breaking their neck first is not a nice way to die at all and they do know about it and will feel it, so I shoot mine first then slit their throat and hang to drain, then pluck and hang for a week, then gut etc, they tasted sooooo nice - I would never go back to shop bought ones again!

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This year I got 3 bronze hens to run with the best stag I hatched last year who I kept, I have 8 eggs due to hatch under a broody next week - I can't wait!
If you want to read up on them a great book about turkeys is Katie Thears one - very handy and of course the net. Mine are out with my chooks on an acre but they don't need all that space if you don't have it, they share the chook house too, they just need extra space to roost as they will pick on the chooks either side of them as they seem to want the whole perch to themselves! You also need to worm more regularly if you want to keep them long term with chickens because of histomoniosis - think that's how you spell it!!

- or blackhead disease.
I'll be putting my stag in the freezer at the end of the breeding season - apparently their fertility declines a good bit after their first season so not much point in me feeding him all winter, so I'll get a BB bronze this time I think to put to my 3 girls next year, then they'll go in the pot at the end of the next breeding season and I'll buy in some new hens.
They are pretty hardy birds and don't need anymore than a chicken would do shelter wise so no need to put extra cladding/heating in winter or anything.
They do make great pets though, if you don't want to eat them, as the are very friendly although a bit dim, or at least the stag is!, but the hens follow me everywhere in the orchard, the stag just spends all day displaying to anything that moves and has a thing for my indian game cockerel!! :lol: