Either the Speedbeez or the Blade Tech holster will fill the bill - but you want to stay away from the competition, speed holsters with the cut down front. Here's why: The 4" Model 28 will be more competitive in IDPA matches - still at a slight disadvantage, but not as great as trying to use it for USPSA. So you want to get a holster that can be used for both.
In USPSA, if you shoot major, with your Model 28, that means magnum loads and the long case of the magnum cartridge does not lend itself to speed, especially since you will be using HKS speed loaders. You will be shooting against .45 ACP revolvers with more of a push recoil, than the sharp snap of the .357, plus they will be loading with moon clips - very fast. If you decide to shoot minor, you are doubly cursed - six shots vs. eight, and again, speed loader vs. moon clip.
The way to go with your gun is IDPA, Revolver Division, minor PF using speed loaders. The HKS loaders are not as fast as Safariland Comp III's or Jet Loaders, but at a beginners level it will only be a minor hindrance.
I don't want to dissuade you from trying USPSA or IDPA, I'm just pointing out what you will be up against. Your Model 28 will be a fine revolver to get acquainted with the game, but don't spend a bunch of money on it, because you really can't correct its non-competitiveness. The idea is to shoot what you have until you are sure that you like the game and are going to stick with it. That also gives you an opportunity to see what your competitors are using and what works best - then spend the money on a more competitive rig.
I'd get either the Blade Tech or the Speed Beez holster, as long as you get the ones that are approved for both IDPA and USPSA. That 4" N-frame holster will also work with a Model 625, which would be a good gun to move up to when you decide the games are for you. Major caliber, moon clip loaded and can be competitive in both IDPA or USPSA.
Good luck with whatever path you choose.
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