Others have done it, but a 92 full sized 18 round flush fit fits in a 5906 just fine, and a 92 compact 15 round MecGar fits in a 6906 but sticks out maybe 1/4".

Anyway, any ideas how to locate the Smith magazine catch notches in the 92 magazines? I have Dremels with cut-off wheels to cut the notches, and diamond needle files to finish the cuts.

Exited to have 15 round magazines that fit my KelTec P-11

You could use Dykem or other similar layout fluid (or Sharpie) to stain the magazine in the area of the "new" cutout, then insert and remove the magazine several times. This should reveal the path of the tooth on the release lever, and where it terminates.....which would be the location of the new cutout.

Be sure you replicate the size, position and shape of the original cutout as best you can using your hand tools.

__________________
Ret. LE, FA Instr, S&W Armorer

Got to ask why? Mecgar makes both 15 and 20 round mags for the 5900 series

Mec-Gar S&W 5900 Series/915/910/659 9mm 17 Rd. Magazine, Nickel: MGW

__________________
Ret. LE, FA Instr, S&W Armorer

That should work.

I remove catch from frame, noting where 'catch edge' lays.

With slide off, seat conversion candidate in frame. Set barrel
on frame in full rearward 'feed' position. You can use a dummy
or live round in mag, to check feed angle. Once it eyeballs
right, scribe a line on mag tube thru the open mag catch hole.

I use a combination of dremel-type diamond cut-off wheels &
bits and needle files to cut.shape the new slot.

The Smith 9mm & 40 double-stack mag slots are well away
from the Beretta 92 slots, and modded mags still work in a
Beretta.

Haven't tried it on any other Smith autos, but worked on my
SD9VE, too...three catch slots, works in 92, 6906, and Kel-Tec
P-11.

For me, it was mostly a winter-weather "gee, wouldn't this work?"
type thing. And, that Uncle Sammy bequeathed me a fair number
of M9 mags

15 round, almost flush in a 6906? 18rd flush in a 5906 with anti-friction coating same price as a 17rd flush fit Non-coated 5906 mag?

And best of all, 15 rounds with small adapter, in a KelTec P-11, which is the same size as the Hellcat, but holds more rounds.

But the big deal really is an alternative to scarce OEM 6906 magazines. I have a bunch, but mags are wear items that are consumable.

It should still work in the Beretta too, so one mag for a couple pistols. I bought a Beretta 92S in 1983, carried it in law enforcement all the way through the rest of my career in 2008. The mag release is down at the bottom of the grip, not behind the trigger guard where the later models and most pistols have it. Soon, all of the Beretta mags were coming with the release cut up high. When I purchased several new mags, I had to cut new slots to work in my pistol. Getting it lined up properly is not difficult if you pay attention and go slow. Good luck.