Since I don't carry a hand gun while riding. Use to carry rifles and shotguns years ago, but never found a real use for a handgun
Found that a 20" double barreled 12 ga more than took care of anything I could possibly encounter (including deer when in season
). Of course your only options are a scabbard or to sling it (sling giving you the option of it on your person or your saddle)
Today I don't take anything (although I'm thinking of getting a tradition recurve bow and move to mounted archery). Decided I'd give the ears of my more recent horses a break
so no more firearms. Although today, with the popularity of mounted shooting competitions, they have ear plugs for horses which is certainly more than we had back when I use to hunt mounted (although I don't think I'd have used them while out riding the roads and woods to hunt so it wouldn't have mattered).
Anyway, for those in love the Glock (even though I prefer revolvers) I'd recommend the CZ 75 over the Glock. And if you want the compact Glock go with the CZ 75 P07 Duty (the standard mag holds 16, so you're 1 up on the Glock there too). With both clips and starting with one in the chamber you'll have 33 rounds (if you honestly need that many so you can send a stream of lead down range.....and scare the poop out of your horse and anything else within 25 yards.....even if you miss
). Also has enough weight to it that you can go through 100 rounds and your hand doesn't feel beat up when you finish.