Since search is limited.  Who makes the best colt smg mags?
Thanks

Colt...

9 m.m.?
Metalform or the re branded ones.

Promags dont feed when it's freezing outside.
C Products that I own, seemed to need break in time.
YMMV.

I really like the Brownells Colt 9mm pattern mags.  I have a dozen and have had zero problems.

Metalform also makes the Palmetto State Armory version

This. PSA branded  Metalforms and PSA mag well adapter have been humming along for 1000’s of rounds.

Not to thread jack, but has anyone had luck with the pro mag drum for colt smg's?

and to answer the op question, my answer is metalform.

Plus 1 on metalform mags from cdnn

No problems with my Duramags (c products) I have a bunch of ASC mags and had to file the feed lips down to get them to work, but they have been 100% since then. No experience with the metalform mags

If you have the milling jig.... just cut a slot in an Uzi magazine for ultimate indestructability and reliability. No BHO, however.

Metalform are the best.
My old Cproducts I had to mill about .032 to lower the magazine.

Just adding to the Metalform recommendations.  They are the standard by which everything else is judged, in my opinion.  I had gotten out of the 9mm AR game in the mid-2000s, but came back in the mid-2010s.  I stocked up Metalforms for my current gun.

Had a bunch of RRA-converted Uzi mags that worked pretty well.  You lose the LRBHO but a properly-converted Uzi mag is usually a solid choice.  Cheap Uzi mags are still out there, but will likely require some cleanup effort on top of cutting the catch.

I had a ton of bad experiences with the CProducts 9mm mags.  I remember those were so hotly anticipated back when they first came out as a cheaper alternative to Metalform/Colt.  And they suuuuuuuuuuuuuuucked.  Then the CProducts legal drama llama showed up and the company flaked out on their initial efforts to "fix" them.  Some folks had luck with them, but you had to get your mag block just right, or tweak the mag catch slot just right, or they misfed constantly.  Sold the two I had for a song just to be rid of them.  The current CProd mags are OEM for IWI's 9mm Tavors and Colt's 9mm ARs.  Big endorsements I suppose, but I don't trust them after my early experience.

I tried a Promag, and it was terrible.  I give them credit for stuff like the HK93 mags, but their Colt-style 9mm mags were straight up garbage.  I think I ended up throwing it out.

Definitely NOT the ProMag (not surprising) poly ones.  They crack at the feed lips.

I got gifted an original colt 9mm upper and it came with duramags. Have about 15 of them and they all run flawlessly.

I found one of the promag drums on sale for $58 and FO'd. Wouldn't ya know it the damn thing ran. I'm not about to run more than one load through it right now, but it's looking good. Typical chinsy plastic promag construction and I may have gotten lucky, but I'm optimistic.