Yes, everything is possible... but this poster, doesnt have a firearm, and is trying to give 'us' the impression that he/she know nothing about guns... do you get them at a gunshop??
Doesnt pass the sniff test especially the part about the mags....
If it wasnt so suss, I would have suggested seeking specific advice 'offline'.... and/or making application from the authority under the firearms act to possess and use a high capacity mag. But given that the poster's naivety suggests a teen who's just finished school and is bored, or a snooping/fishing LEO.... I dont see the point.
As far as nothing's banned; thats how it is; we have licensing categories (and therefore licensing) for most everything, even auto rifles and auto handguns. You can own them under 'normal' cat A/B licences.
Most rifles have a detachable mag limits of 10 or 15 rounds (no limit for fixed/internal).... but there is always provision to seek a variation to this.
I would say there are many thousands of semi-auto rifles around the country(cat D), that survived the great firearms purge of '96...even auto(cat E). It was said that back 'in the day' a certain importer brought in container loads of semi autos including M1Carbs.... one shipment were (unknowingly) autos
.... I wonder how many were handed in...
The category covering 'machineguns';
-definitions-
category E longarm means any of the following—
(a) a machine gun that is a longarm;
(b) a tear gas gun or projector;
(c) a shotgun or rifle with a length of less than 75 centimetres measured parallel to the barrel;
(d) a mortar, bazooka, rocket propelled grenade or similar large calibre military firearm designed to fire an explosive or projectile or any other similar prescribed firearm;
(da) a cannon which is not a black powder ball firing cannon;
(e) any other firearm prescribed for the purposes of this category;
(f) any other firearm that is declared under section 3A(1) to be a category E longarm;
(g) any other firearm that is declared under section 3B(1)(b) to be a category E longarm;
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section 10
(5) The Chief Commissioner may licence a person to possess, carry or use one or more category E longarms for the reason specified in the licence.
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Section 13
Reasons for applying for a longarm licence, category E
(1) The Chief Commissioner must not issue a longarm licence for category E longarms unless—
(a) the applicant can demonstrate that the licence is required for an official,
commercial or prescribed purpose or for a purpose authorised by an Act or regulations; and
(b) if the application is in respect of more than one category E longarm, the applicant can demonstrate a compelling reason for more than one such longarm to be possessed, carried or used under the licence.
(2) For the purposes of demonstrating that the licence is required for a purpose specified in subsection
(1)(a), the applicant must produce evidence that the licence is required for that purpose.
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Cat E can be owned under a collectors licence, however must be permanently castrated.
everything is do-able
If you're a pro-shooter they make sense but as a recreational shooter I don't see the point. He has a goal of making a living from shooting and should be encouraged in his pursuit. 
needs a 30 round mag for a 7615 .223 
