I noticed that Springfield just came out with a new XD, the XDs .45 ACP. I saw a youtube video from NutNFancy's visit to the SHOT Show 2012. The term 'Single Stack' was used to classify the handgun.
Does 'Single Stack' refer to the clip/magazine? I only have hands-on experience with a Glock 22, its a buddy's gun, I'm assuming that that clip/magazine is a 'Double Stack' because the witness holes; is that correct? Also assuming, that a 'single stack' clip/magazine isn't a new thing what manufactures make a 'single stack' 9mm? I'm open to any make not just Springfield or Glock.