I have a late 60's M41 (original owner) with one of the two original magazines with the steel follower. The other died in the CCI hi-velocity exploding case episode of a couple of years ago - that thread seems to have been lost in a general re-do of this forum.

CCI replaced the destroyed magazine with a late model red follower type, as well as replacing the destroyed grips.

I had it at the range last week for the first time in ages, and had to stop using the red follower magazine because of repeated failures to feed completely. The rounds would not get fully seated, and consequently the gun would not fire. The magazine spring is considerably stronger, and I'm guessing that the M41 has trouble stripping off the new round with the extra pressure on it. There were no failures to feed in almost 300 rounds using only the old, original magazine.

I'll be in the market for a couple extra of those older magazines.