Hammer rifles and bags (9)

I believe the answer is:

knapsacks

I'm a little stuck... Click here to teach me more about this clue!

'bags' is the definition.
(knapsack is a kind of bag)

'hammer rifles' is the wordplay.
'hammer' becomes 'knap' (I am not sure about this - if you are sure you should believe this answer much more).
'rifles' becomes 'sacks' (I've seen this before).
'knap'+'sacks'='KNAPSACKS'

'and' is the link.

Can you help me to learn more?

(Another definition for knapsacks that I've seen is " bags".)

I've seen this clue in the Sydney Morning Herald.

Want a hint initially instead of a full solution? Install my app