All you do is set the round on the follower and push it down until it seats under the rail. Then the next one gets pushed down until it seats under the other rail. Repeat until the mag is full. Just make sure the base of the cartridge is against the back wall of the magazine box. Been the most simple and reliable set up since 1898 iirc.
A double stack detachable mag loads exactly the same. A single stack mag requires you to press the cartridge down and rearward against the follower .
Old timers tip for fixed internal box mags !!! If you want to load the mag but not have a round in the chamber push down the top cartridge so that the bolt will close over it leaving all the cartridges in the mag but the chamber is empty. You may have to load one less than the absolute total capacity for this to work.
You will have to have a stock with the cut out, and a box mag and proper trigger guard.
I agree- no difference in loading a DBM or an ADL. Slide the cartridge to rear and they feed perfectly. I prefer the ADL (I have two) BC of the smooth bottom. Four rounds is plenty for any hunting situation I will ever be in.
It may be easier to buy a new stock and bottom metal if you are not so handy.
Only one of the 3 pieces are the same between ADL and BDL in the magazine I think, suddenly I can remember which one is the same, the spring or follower.
Then you would have to inlet the stock to accept the BDL metal. You would no longer use the small screw in front of the trigger guard or the small screw that holds the box to the action of the ADL.
Yes, you can do it, it just be more practical to shop some used bottom metal ($150 new) and pick up a stock of some kind depending on what you want.
well after reading to OP again that is what he wants. The MagPull would fit in the BDL inlet. If you wanted to use a factory detachable mag additional inlet would be needed unless it was say a factory or Houge with it already cut.