Winchester usually makes a run every couple of years, or at least they used to.
"If" you can find some "Winchester brand" 5mm Remington magnums rimfire ammo, You better hold on to them, as i don't think they EVER made any, let alone "every couple of years"!!!
BTW, i have several boxes of Rems. i'd sell for $60.00 per box plus postage, PM me if interested.
Drilling Man