Overview of the UK/US gun reform:

US gun laws are brought more inline with the UK gun laws

Only sport shooting allowed

Break action centerfire rifles are legal

Bolt action centerfire rifles are legal

Straight pull centerfire rifles are legal

Semi automatic rimfire rifles are legal

Pump action rimfire shotguns are legal

The rest are illegal

UK gun licenses are not blanket licenses anyway

US gun licenses are simplified into an age 18 long gun license with full control or a prohibited gun license (for maritime and museums)

While the UK long gun licenses are not simplified in the reform, the age requirements are to prepare for the U.S.E. under DC law

Borrowing rifles/shotguns with supervision is set at age 16

Borrowing airguns with supervision is set at age 14

Raising the ages for most gun requirements but lowering the age for supervision to age 18 (to satisfy the US NRA and thus the future U.S.E.)

DC minimum long gun lengths are a 16 inch barrel and 26 inch overall length for rifles, and an 18 inch barrel and 26 inch overall length for shotguns

UK minimum long gun lengths varies for specific guns and will remain unchanged until the U.S.E.

So in laymen terms it's English/Scottish NRA standards for the American NRA (and UK gun laws mirroring the new US gun laws)