Two magazines problem
 

My DWM pistol has the hold open lever. One magazine, a Triple K brand works flawlessly. The other magazine, an older replacement type does not hold open the toggle. Visually I can see little difference except one measurement. At the rear of the magazine follwer there is a pronounced lip. On the Triple K the lip is .023 high; on the other it is only .013 high. Would this make the difference? Just what part of the magazine trips the hold open lever? Any help appreciated. And, thank you

The button on the side pushes up the hold open lever.
Some replacement mags are made with an "under-diameter" button; hence won't work the hold open.

Easy fix=different magazine.
Sometimes you can activate the hold-open by pressing up on the magazine bottom to raise it in the mag. well.
dju

Further examination of the 2 magazines: the one that does not activate the hold open has a larger diameter button that extends out further the the Triple K button. I can't figure out why it doesn't work tho.

Sometimes they get stuck in the grip channel. Also if the mag spring tension is very weak, the holdopen will push the button down instead.

Try it with the right grip removed. That will also give you a visual.

So then, where to buy proper magazine spring?

I wouldn't bother trying to fix a mag. Get a good MecGar for shooting.

Wolfgunsprings.com

Has mag springs and lots of others.

GT also has replacement round springs.

It's difficult to disassemble and successfully reassemble Luger magazines without the correct mandrels and tools. GT offers a rebuild service that is worth the cost.

it's less costly to buy a replacement magazine that works for a shooter.

Mecgar!