G'day gents. I thought I'd buy into this as well.
My understanding is Sig & Browning pistols and AUG Rifles are issued to the commando regiment (reserves), H&K USP & Browning pistols and m4 carbine(?) are standard issue with SASR.
One of my mates is in the commando regiment, I'm holding a USP for him while he awaits his civilian licence, he bought it so he could practise with what the 'big boys' have.
Regardless of who got their story right, and I don't claim to be an expert, I think you may all enjoy looking at
it's the site for the unofficial SASR IPSC team.