[CompanyMan]

I have an M17, which came with 2 21 rd mags (and a 17). What are the best options for more (want, not need) rounds?

So far I have found:

Extensions:
Springer Precision (makes a +10 for $50) or Taylor freelance
Expensive, uneven profile may affect mag pouch fit,

Aftermarket mags:
ETS 30 round ($20) early reports of not dropping free, not feeding last round.
May have bbe fixed by now? New spring and follower may fix?

Promag makes one, but even with a new spring and follower I wouldn't have
warm fuzzies. Most mags they make for most guns are trash.

Am I missing any?
can anyone with PERSONAL EXPERIENCE chime in?

 

[Twister]

I decided to give a ETS mag a try but the mag release will not lock into it in one of my 320s and it won’t even fit into the grip on the other, done....

I did put a TT +3(?) extension on a 17 round mag and it works fine in my X5 grip.

 

[Nilla]

While I don't have the Sig P320 I do have P229 9mm, P226 in 40s&w and 9mm I've found Sig Sauer magazines at good prices and in stock here on https://www.scheels.com

Here the link for P320 Magazines also https://www.scheels.com/search?q=sig p320 magazine

Hope it helps.

 

[JamesPettigrew]

I would stick with the sig 21 round mags that you KNOW will work.

 

[Buds]

First off I do not have a firsthand review of any magazines other than Sig Mags.

Here is the Springer Precision +10 Baseplate:

https://springerprecision.com/p320-9mm-10-base-pads/

I do not see a review of this setup on youtube but usually Springer Precision mag Baseplates seem to function fine.

At $54.50 to add 10 rounds you can easily purchase a 21 Round Mag from Sig and still have $10.00 in your Pocket.
It is not a option that I would choose but that's just me.

As far as ETS Magazines there are a lot of reviews about them on youtube..

https://www.youtube.com/results?search_query=ETS+30+Round+Sig+Sauer+P320+Magazine+

I did not see a review for the ETS 30 Round Sig P320 magazine @ $21.99[/B]
Part # SG9-320-30

https://www.etsgroup.us/ETS-30-round-9mm-mag-fits-Sig-P320-p/sg9-320-30.htm

Good luck in your quest for a larger capacity P320 Mag.
Hopefully someone will have a first round account for you.

 

[DirectDrive]

I would stick with the sig 21 round mags that you KNOW will work.

This ^^^
I have Springer +10's on 17's (they're really +9 w/o Grams kits) for the range.
Carrying Springer 26rd mags would be a thinking error.

 

[DBX]

It may not be the number of extra rounds you want (+10 or so). But Taran tactical makes P320 base pads, +2 for 21-round, and +5 for 17-round. They are designed to fit 140mm gauge for USPSA CO and limited division.

https://tarantacticalinnovations.com/base-pad-for-sig-sauer-p320-9-40-magazines/

I use the +2 for the 21-round. The mag remains almost identical length but now holds 23 rounds. It uses factory spring and functions perfectly so far.

 

[ddc]

It may not be the number of extra rounds you want (+10 or so). But Taran tactical makes P320 base pads, +2 for 21-round, and +5 for 17-round. They are designed to fit 140mm gauge for USPSA CO and limited division.

https://tarantacticalinnovations.com/base-pad-for-sig-sauer-p320-9-40-magazines/

I use the +2 for the 21-round. The mag remains almost identical length but now holds 23 rounds. It uses factory spring and functions perfectly so far.

Just for fun I put the TTI +5 base pad on a 21 round mag.

Functioned fine with the TTI spring. Didn't try the factory spring.

I guess I could use it for the nightstand gun.

 

[DBX]

Just for fun I put the TTI +5 base pad on a 21 round mag.

Functioned fine with the TTI spring. Didn't try the factory spring.

I guess I could use it for the nightstand gun.

Wow, interesting try. Didn't even think about it and didn't know it would work.

I probably won't use it for nightstand when 100% reliability is needed. Besides, it is hard to fathom a situation when 21 rounds isn't enough but 26 is...

 

[ddc]

Wow, interesting try. Didn't even think about it and didn't know it would work.

I probably won't use it for nightstand when 100% reliability is needed. Besides, it is hard to fathom a situation when 21 rounds isn't enough but 26 is...

I agree. If 21 doesn't get it done I'm in trouble.

Plus it was on a compact frame and slide which made for a rather funky looking combination... lol...

 

[Deadpool392]

I have the ETS mags (1 17 round and 1 21 round)that work ok. I only use them for the range as I wouldn't trust their quality for carrying. They will not drop freely from my P320's and they are prone to sticking when I insert them unless i press the mag release as I insert. The 21 round mag also alters the ejection pattern and cases casing to impact my Romeo 1, not sure why that mag causes it though. I bought them to try out of curiosity, i have plenty of mags for my P320's.

 

[DirectDrive]

Any P320 mag with the "notorious notch" at the bottom of the tube will not be a good candidate for a mag extension.
For example, the excellent 17rd ACT-MAG's have this notch and the spring gets caught in the notch and stops rounds from entering the extension.
I believe that some of the 21rd mags have this notch.

I used Checkmate and MecGar manufactured 17rd SIG marked mags with my +10 Springers. (no notch on these)
Note that the Springers require a divot be cut into the tube base flange to allow the Springer set screw keeper to pass through.
I used a Dremel "burr" (cutting bit) that was 1/16" in diameter (steps down from 1/8" shank).
It's a tiny scallop cut that is required for the Springers.

 

[BigRed502]

Henning Group has a extension for the 320s out recently. It is a +3 extension I believe. For reference, they are the company which makes the Legion base pads for sig. I have a couple of them ordered but have not tested them out yet.