I know .40 isn't as popular with private citizens anymore so a lot of people probably will not care, but why does the full size Sig P320 in .40S&W hold 14 rounds, only one more round than the P320c??  Their full size gun is 5.5" tall, and their full size 9mm holds 17 rounds, same as their competitors, (M&P, Glock, etc).

Most full size 5.5" height .40S&W pistols hold 15 rounds like the M&P, G22, etc.  Heck, Springfield's XDm holds 16 rounds, though it is a 1/4" taller than the others.  I just bought a conversion slide and am kind of irked as to why and what reason capacity is being denied by one round compared to all other comparable full size guns?  Usually a mag large enough to hold 17 rounds of 9mm can be designed to hold 15 rounds of .40S&W.

On the other end of the spectrum, it's surprising that their P320c .45 holds 9 rounds, only one less than the full size and one round more than competitor's compact .45s!  I handled a P320c .45 recently, and was surprised and impressed that such a small compact frame can accommodate 9 rounds of .45 when S&W and Springfield's comparable compacts of the same size can't.

Seems very inconsistent.

I'm not an expert on P320, only have a 9mm carry model.  But if I had to guess, maybe due to the interchangeable frame grip sizes?  Not talking about going from carry to compact or subcompact, talking about just the swapping of frames.  I would assume having the ability to go from large to medium to small gripped frames where they are changing the entire frame instead of just grip back straps or side panels like other manufacturers, might require them to design their magazines differently to fit all three grip sizes.  Just a guess though, I'm new to Sig handguns and it's been interesting trying to figure out all their different variants of each of the models.

SIG and HK seem to play conservative with their magazine capacity.  The P228 and P229 originally had a capacity of 13 in 9mm.  You could get flush fit aftermarket Mec-Gars with 15.  Now the P229 ships with 15.  You'd have to ask someone from SIG exactly why, but I suspect they sacrifice some capacity to ensure proper feeding (whether the follower is larger, or the spring doesn't get as compressed or whatever).

If it bugs you that much, just think back to AWB era and be thankful that you can have more than 10!

It's well known 229 9mm used to be built on a carbon copy of the 228 frame, and then they switched to using the 40/357 frame for all 229's so they only had to build one frame. which is why old 229's use 228/229 magazines and new ones use what they call 229-1 magazines.

as for 320s... who the hell knows. I'm really waiting for mecgar to start selling mags for them under their own name. I live in NH and go to the Sig proshop for mags. 320 compact mags are always out of stock even at Sig.

I wonder if that will happen now that Sig has won the big army contract, it might be against their agreement to allow mecgar to sell mags under their own brand name.  

The Glock 17/22 and M&P 9/40 are basically the same frame, so I don't think it's that.  For some funny reason, it reminds me of the EAA Witness Tanfoglio 10mm pistol.  The first mags were not mecgar made and held 15 rounds but had reliability issues.  Mecgar then got commissioned to design a magazine, and they made it with a 14 round capacity.  If 15 rounds works and feeds reliably with glock, Springfield and S&W, you'd think it would be something easily implemented.

I'm sure that is the case, they dont sell the 229-1 15 rounders under their own brand either. I'm sure with the army contract shitty pro-mags will be made and flood the market.

I still see no reason why a full size 5.5" pistol in 40S&W can't accept 15 rounds like every other full size.

I'm fine with the 14 round flush fit, but I'd really like to see the 18 round extended mags (like the 9mm 21 round mags) get released. More would be better!

One less capacity due to mag taper at the top??

The sig 320 mags seem to have a longer tapered shape from the top down, than a similar size mag from, for example, a glock.

Maybe the taper/angle of the cartridge column has led to one less capacity?

That's what I think it is, honestly!  I think it has to do with how Mecgar designs their mags.  Glock, Springfield, and Smith and Wesson are the same size but have their mags designed differently to allow for the increased capacity.  

At least their 9mm's are the same capacities as the rest!

I could take your first post and claim it as mine.  I have the exact same questions you do. Drives me nuts. I hate that Glock is the only natural mag capacity. 17-9mm is 15-.40 is 13-.45.  Just makes sense.  The rest of the Glock I wouldn't melt down to use as raw material for the Sig.

gun mag warehouse claims they have them.

Based on personal experience, the 13rd 40 mags seem to be maxed out much more than 15rd 9mm mags. As in the 13th round BARELY fits in the 40 compact mag. I assume the small increase in length between the compact and full size mags isn't enough to fit another 2 rounds. But yeah, I agree it's annoying it doesn't hold 15 rounds like Glock.

And yet they manage to fit 13 rounds of the .40 S&W in their compact, but can't / won't allow the full size to accept 15 like all other .40 S&W full size pistols...

One extra round isn't worth the grip size increase from compact to full.  


Another interesting note, their 140mm "game reg length" 21 round 9mm magazines "only" hold 21 rounds.  Other comparable 140mm 9mm mags hold 22 or 23 rounds.  The 21st round fits very easily into the Sig mag with little effort, I'm sure they could have designed it to accept at least one extra round.  In fact, here is a company that offers a +2 base plate for the Sig P320 21 round 9mm mag that keeps the mag in the 140mm overall length, but allows a 23 round capacity!

http://shop.springerprecision.com/product.sc?productId=383&categoryId=45

Thank you, ordered 2!!
For anyone interested, ammunitiondepot.com also has them, but the shipping was a tad more through them.