greetings, I want to acquire some more 17rd mags.  I see pro-mag and armscor/rock island (act-mag) make them (at least).  Any concerns with using either ?  recommendations ? other brands ?  I looked through the fine manual and there's no mention of any form of using aftermarket mags (just in case SIG wanted to say something about it).

pardon the ignorance, rock island used to be a thing a while ago.  does the name imply good things about the quality of the mags they're selling ?  "act mag" sounds a little dubious, but, don't judge a magazine by its name ?  "pro mag" doesn't sound much better...  good or not ?

I'd NEVER buy or use anything "Pro-Mag" - Period.

ACT - Rock Island ?  I've had great luck so far with their M&P Magazines, so I'd be willing to try their Sig P320 / M-17 mags.

Rock Island USED to be a US Government Owned Armory making guns for the US Armed Forces, but like Springfield Armory, it was closed and those names sold off to completely different private companies that had nothing to do with US Military Arsenal Production.

Bigger_Hammer

The ACT Mags are fine.

I have several hundred rounds through the new Magpul Amag (stainless P320 mag) they are good to go. They can be founds for about $26 if you shop.

ACT-Mags have run perfect for me.  I've got four of them.

I got conned into trying some ETS mags.  They're absolute trash.

The ACT magazines are an excellent product and great value. Here is a fairly extensive discussion about them from a few years ago:

P320 9mm mags

The only caveat I’ll offer is that a few members reporting having issues with them feeding when training with them outdoors and dropping some in the dirt. Their experience was that some dirt and debris could get inside them and cause the follower to stick. A possible cause was that although the ACT mags look nearly identical to factory P320 mags, their spring has one less coil than the factory mag. That might make them a little less powerful when trying to push through internal debris. I mentioned that in this more recent thread and shared a comparison photo:

ACT-Mag? What, where, and do they work?

For that reason, I use ACT mags for training only and stick to factory mags for carry / home defense. I really like the ACT mags though and use them on every range trip. They are certainly much more affordable. Greg Cote and Mag Shack have the best prices on them.

Look for change under couch cushions.  Buy factory mags.

ETS mags are garbage, MagPul's new mags seem good to go if you don't mind that they're stainless with black base pads.  

Otherwise, buy OEM mags.

Agree with everything—ETS suck, ACT and Magpul are good to go.

You can't beat the ACT-Mags for their price point. They are worth more, as far as quality goes, in my opinion.

Magpul 17 rd mags are best bang for the buck for 320. Wouldn’t use any other 3rd party non OEM. I have about 400 rds spread through 4 magpul 320 mags and they are great. No issues

The ACT mags are the same Italian mags as other ACT mag products.  It seems Advanced Tactical being a source gets them associated with Rock Island and the Philippines.

The only real noticeable difference between the Mec-Gar and the ACT P320 mags is the ACT mags have a shiny blued finish while the Mec-Gars are a matte finish.  Some Mec-Gars for other guns have the same shiny blued finish.

The 17 round Mec-Gar has a very strong spring and is identical to the one used in the 21 round mags.

The 17 round ACT mag has either 2 or 3 less coils on the spring than the 17 round Mec-Gar.  It’s the same length as the ones in my 17 round M&P ACT mags.

So much this, unless there is some unobtainium no other choice pro mag is the only way you could possibly get a mag, even then don't get pro mags, roll you own out of tinfoil and a Bic Pen, just as likely to work 100%.

They are just one coil shorter. Here's a comparison of a new ACT mag and a new SIG Mec-Gar that I posted in another thread. The designs are slightly different also where the springs transition from skinnier, single stack width loops to double stack width, indicated by the red arrows. The SIG Mec-Gar spring transitions closer to the top, which could reduce the risk of binding in the narrow part of the spring.

Attached File

y'all are great.  I'll let you know how I make out.

Just saw on Instagram that Amend2 makes P320 mags.  I think maybe they were just released?  I have not tried them, and with ACT making awesome, inexpensive mags I doubt I will unless they start making stick mags (for my Flux Raider).   https://amend2mags.com/amend2-a2-320-17-round-magazine/

I wish the magpul mags were some type of black coating instead of raw stainless. I wish they had other base pad colors like coyote. But what I really want is them to make a 21 rounder.

Here's hoping we'll get that eventually, but MagPul is always so inconsistent with their support for "other" colors.  OD and Gray are damn near impossible to find, and even FDE/MCT is incredibly hit or miss on the stuff they do make in those colors.  I've never even seen MCT .308 PMAGs in person.

So I ended up buying 7 of the 32 round Pro Mag P320 mags after speaking with B&T about the APC9 and GHM9 with the 320 lower. The factory 21 and 30 round mags both made by Checkmate and Mecgar were failing to lock back on empty in my GHM9. The 17 round Mecgars and ACT mags worked fine and locked back on empty but the 17 round factory mags made by Checkmate failed to lock back on empty and would sometimes have a last round failure to feed. Apparently B&T tested all of the P320 mags available thinking the Army would want the P320 lower for the APC9. Obviously they didn’t but it turns out from their testing the Promag P320 mags were 100% reliable and locked back on empty 100% of the time. After 2K rounds through my GHM9 with the Promag 32 round mags, that has also been my experience. I ran roughly 1K rounds through one of my P320s using the 32 round promags and they were 100% reliable. The only issue is the AFC on the mag bodies, isn’t. It’s applied very thick, this caused the mags to not always drop free. The other issue was the mag would rattle. I typically only loaded 30 rounds in the mag but even with 32 rounds, some of the 7 mags I had, roughly 3 would rattle when loaded to 30-32 rounds. I’m sure this is some sort of spec issue but it did not affect function. While I won’t be replacing my standard mags with promags, I thought I’d share my experience with them. I think they make a great range mag especially for $20.