You shouldn't call Bullets 'Bullet Heads' it's an uneducated response.
Some retailters (in the UK) call them that as they are dealing with dumb people who don't know any better or are too ignorant to learn the correct terminiology.
Reloading is a precise and complex activity that needs care and attention.
Bullets, you can buy thousands of them if you want to.
Brass cases. you can buy thousands of those too.
Primers and powder fall into a 15kg Net Explosive Quantity (NEQ) limit, above which you need a special licence.
5,750 primers = 300g of explosives.
Most RFD's will sell you 1000 if you have a need and are 'known' you may be able to buy more.
Powder has a similar limit. an RFD will likely sell you a few KG's to start with.
When you combine all these componets into a 'round of ammunition' then this is subject to your FAC limits.
If your FAC says you can have 80 rounds of .243, then you can only have 80 rounds of .243 ammunition in your possession.
It is quite an expensive hobby, very satisfying, quite difficult to get it right and be consistent ..
Don't call Bullets 'Heads' or 'Bullet Heads'.
The 'head' contains the primer which sits in the primer pocket.
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