Please forgive me being a bit of a pedant on this, but the proposed amendment was to put reloading components into section 5 of the firearms act (weapons subject to general prohibition) and that section does indeed state that "without authority" an offence is committed if a person owns, possesses or acquires any of the items listed in section 5.
Section 5 also states that the "authority" is the secretary of state or the scottish ministers.
The police and FACs are not mentioned
Section 5A provides exemptions to section 5 where the "authority" of the secretary of state is not required, and in certain cases possession of an FAC is sufficient "authority".
The most well known exemption where possessing an FAC is sufficient authority being expanding ammunition
However, there was no proposed amendment to section 5A meaning that, if the amendment had become law without an equivalent amendment to section 5A allowing FAC holders to own. possess or acquire reloading components, then it would have been necessary to obtain permission from the secretary of state or the scottish ministers to own, possess or acquire these components and an FAC would be insufficient.
That is exactly the situation we have with legally held handguns - permission comes from the secretary of state or the scottish ministers and not the police (although the secretary of state and/or scottish ministers can involve the police in the decision making process)
Cheers
Bruce