I’ve got a Ruger P90. Factory mags haven’t been available new since around 2020.
1911 mags seem to fit and feed but the catch slot is different and in the wrong place. A few old threads found a couple people have cut a new slot in a 1911 mag and it worked fine.
Whats the best way to cut a new slot in a 1911 mag? I have a Ruger mag as a guide.
Rotary tool?
I thought I’d find a guide for a similar project easily but, nope.
That would be what I would use. Interesting, I haven’t seen a P90 or even a P89 in a long time.
I would 100% be thinking cut off wheel in the dremel machine. But damn. If you could find someone with the laser cutter it would be better. Not sure how they work of if that would be possible on a non-flat piece of metal.
Drill, then open the hole to the desired shape.
Machine shop would(almost) always be the way to go to nail the cut right if shop time cost doesn’t kill the deal. Multiple mags at once might be better, maybe?
Ebay has several factory mags in the $50-$70 range such as
Another option is looking around at gun shows. I recently went to my first one in over a decade and thoroughly enjoyed looking at the historical items.
Dang, makes me feel old. P90=historical item 
. That’s like the first time I heard Van Halen playing on a classic rock station- I was like WTH?!!
Me, either!
I bought it just because it was in excellent shape for $300. It’s a decock-only version.
Excellent trigger. The DA is better than a 226 / 220 or HK DA.
Oo..i like this idea! Thanks!
I saw and lost a bid on one. This is probably just going to be a fun and / or stash gun. I don’t need many mags for it, especially at $50+ each. But 2-4 extras would be nice.
I got a Promag for it…yea, i know…it fits, though not well, and cycles inert cartridges so, it might actually work well enough for the range. But it’s definitely crappy.
A few quality 1911 mags that fit would be great. I have a nice, 8 rd Mecgar one with removable base plate. That’s the one i want to try and mod.
That sounds like a decent show.
Most shows the guns are 70-85% boringly common.
It is something I’d look for there.
I used to pick on the P series, too. Even though my experiences with them were fine.
I also recently picked up a P94 .40. It too, has a very good trigger and shot very well! Soft, too! These are pretty good guns!
Yea.the P94 i just got has that patina of faded / brown, old bluing on the slide. Like on Dad’s “old guns”.
But my P94 could be over 30 years old. I haven’t looked into that.
I’ve got other guns that old that are also reliable and i would trust to carry.
I spent an hour machining a new slot on the Meg-Gar mag.
The drill idea didn’t work because the bit walked on the rounded surface. Tried to punch a divot, but the metal is a little thick for that. Can’t punch enough of a divot without risking collapsing the body.
So i used a cutting disk. That worked well. The i could enlarge the slot
It all went okay. But it won’t work. The 1911 mag body isn’t as wide as a P90 mag. I knrw that but the difference wasn’t extreme so i tried. But the mag is too narrow.
Oh well. I did some machining on the Pro Mag so it fits much better now. The spring doesn’t seem any weaker than the MecGar or Ruger one and it feeds rounds manually and locks the slide back. Will fire it soon.
Anyway, was worth a shot.
The couple guys who said they made it work? Who knows? People make stuff up.
How much narrower is it?
Could you shim it with something?
I just did some more checking.
It’s not the width. They are all .5445-.545" wide.
It’s the shape. The front of the Ruger & P90 Pro-Mag is much more square than the Mec Gar 1911 mag. Therefore the new groove in the 1911 mag is just too far away from the mag catch.
Extending the mag catch would help, but modding the gun & mags to get them to work together isn’t worth the effort.
If i really like the gun after firing it I’ll know if i want more cheap mags, another Ruger mag, or neither.
If the crappy Pro Mag 8 rd mag works, they also make a crappy 10 rd mag for this gun. Pretty sure they make one longer than that but the odds of it working even most of the time are similar to Voyager One returning to Earth. 
I can report the Pro Mag actually ran perfectly! How about that?!
The P90? Well, it was accurate. I had one malfunction with a soft lead RN reload, and a factory +P round was ejected along with a fired case. Both occurred with the factory mag. Fired about 125 rds.
The gun is a bit “flippy”. Higher bore axis & 230 gr bullets i guess. Grip is too slick. The P94 .40 didn’t rotate so much.
I’m satisfied with the ProMag.
Will keep the .40 P94 until i have no more .40. But the P90 .45 will likely get sold or traded eventually.
Also, the P90(and 85/89) trigger guards are sloped down forcing the hand down. Basically the total opposite of undercutting the trigger guard to better manage recoil.
The P94 doesn’t have that issue.
Man, i didn’t consider that. I need to give that a closer look. Interesting!
Yes, you’re absolutely right.
And now i find that P90 trigger guard shape really annoying. 
I’ll give it another range trip to decide whether to keep any length of time.
Lol sorry
A buddy had a P89 for awhile and I noticed recoil was less manageable than my Glock 17 despite the P89 being heavier so I started looking at differences and picked up on that as a biggy.
Might not be an issue now, but the skinnier early 20’s me got a fairly large gap between the web of my hand and the top of the grip tang because of the downward slope of the trigger guard.
Weird that was done that way since high hand grip mods were already a thing with 1911s.
Never held one, but I suspect an Israeli HI Power(Kareen?) had a similar issue due to what was effectively a upside down beavertail extended tang from roughly the same time frame.