It fits in a standard Ruger M77 long action. i.e. any donor action for a .300 win mag, .338 win mag etc. will work.
We used an old stainless .338 win mag rifle with the plastic paddle shaped stock as the donor.
Not all bullets will fit in the magazine if they are loaded long.
The image below is a 500gr Woodleigh bullet positioned in standard Ruger long action magazine box.
This load has just over 2mm (approx 80 thou) of clearance when the bullet was seated to the middle of the cannelure. The finished rifle feed this load without any issues. We did not make any modifications to the magazine box or feed ramp apart from polishing some edges to smooth things up.
