Have a piece of Blackburn bottom metal for a pre64 model 70 Winchester that has been tucked away for a while. It is 30/06 length and standard depth. Got it out today for a project and it would seem that the bottom of factory magazine box needs to be trimmed for the 2 item to match up.
Have I got this right? It would explain why they advertised them as 4 round and not 5.

I know on the G series classics the magazine box needs to be shortened. But that does not reduce magazine capacity. It just allows the box to sit above the "frame" of the one piece unit.

Thanks Chuck.

I'll try and post a photo of mine here today.

Here is a photo. You can hopefully see how the box sits just above the bottom metal frame and the frame itself then acts as part of the box. No magazine capacity is lost.

I see what you mean. Thank you for taking the time to post the photo.