Mexico has some pretty weird rules, but basically we're restricted to .38 special revolvers and .380 acp automatics. If you take your regular basic nine, and get a barrel made up that duplicates the original with a .380 chamber and a longer lead-in for heavier bullets, you can load the .380 case right up to 9 performance. If it's a 1911 Super or 9 m.m. and you fully support the barrel, you can do 9+P with nothing coming apart.
This "long-slided" Glock 25 will launch a 125 grain Lee RN lead bullet at 1,130 fps all day long without distorting anything.
These .380 acp 1911's with fully supported chambers will exceed the Glock a little bit. The 6 inch version can fire a Saeco 140 grain LSWC at 1,200 all day long. We use small rifle primers for that loading, but we've shot several thousand of them. It's about the top-limit for the .380 case as you basically don't have any more room for powder. They are very accurate.
For our fledgling competitions -- which are just getting started (we hosted a P.P.C. event this weekend with 26 competitors) we separate all firearms into two classifications: SERVICE CLASS, which is any auto or revolver with a barrel no longer than 4.25 inches with or without adjustable sights. Also, we have the TARGET CLASS which are all autos and revolvers with barrels longer than 4.25 inches and shorter than 8.5 inches with or without adjustable sights.
These are arbitrary divisions due to the unique situation we face with the incredibly draconian laws we have to live within, but they work well enough. I am not sure that a 6 inch Model 10 is any less a "service" gun than a 4 inch Model 10, nor am I any more sure than a 5 inch Model 27 is as much a "Target" gun as a 6-inch K-38 but it's the division we make and it works well enough for us so far.
We also have the "SNUBBY CLASS" (the two-inch pocket guns) and the "SUPER SNUBBY CLASS" for the 2.5 inch to 3 inch guns. This Colt would be a "Super Snubby":
Phil's classic 5-inch Pre-Post-War Model 27, under our rules, is a "Target Gun" although it's real-life battle experience was as a service gun on Guadalcanal and Bouganville.
The "Silver Menace" is a long-barrelled K-38 tube mounted onto a round-butt Model 19 frame and marked as a 14-4. There's lots of jokes about Jack Nicholson in "Batman" and his long-barrelled revolver when this one's around.
A Mexican gunsmith reblued this Pre-Model 23, including the hammer and trigger, and when we bought it we replaced those parts with case-hardened versions. It is now the Target Class revolver of one of my best friends.
My own Target Class gun is a Model 14-3 that I have installed an original K-38 H.B. on to, with a Model 64 parts set (cylinder, trigger, and hammer) giving it the two-tone finish. The cylinder has been moonclipped by TK-Custom, and the thumb-latch is one of the excellent S.D.M. latches that really have great surface checkering. The front sight is a .243 red bead that is still sold and the rear is a .160 White Outline.
But you asked about service class guns. My personal choice as a "Service Class" firearm, both for Mexican Shooting Competition and real-life use is my pretty, although used, Heavy Duty. It's got the power. It's got the looks. And it shoots to where the sights point with the "big loads". It's all I could hope for.
So, that's my state of affairs in the "Service Class" situation here in Bananaland.