I'm actually contemplating a 9 major open gun purchase right now. This raises a few issues. Let's break them down:
USPSA divisions
9mm major is only "a thing" in Open. In no other division will the extra velocity get you major scoring while pushing a sub-40-diameter bullet.* I assume you know this, and that we are necessarily talking about open guns.
Open Glocks
I have shot for several years with a guy who had an 9 major open gun built out of a Glock. Well, actually, he used two of those guns - one before a case blew up and the replacement one after. They were built by these guys:
https://stores.sjcguns.com/about-us/ , if I recall correctly. Except for the one detonation, the guns run very reliably. He does go through some c-mores, though.
K.C. Eusebio tried to make open/9 major Glocks work for 3 years (while he was on "team Glock" under contract). They broke a lot (built by a
different smith than the ones I linked to above). KC talked about this in a
Shooter's Mindset podcast not too long ago if you're curious.
By virtue of their flexy frame, Glocks are tough on frame mounted optics, and its also very hard to get the dot to stay in the window with them. And, of course, you can't ever get to the kind of trigger that all the 2011-type open guns will have. But the base gun is cheap, and mags are super cheap. If you can find a smith to do the work/sell you one, you can get into one for around that $2-2.5k range.
Cheap 2011's
There aren't any you can buy new. And the "entry level" ones ($3.5k) often turn out to be finicky. If you look long and hard enough, you can sometimes get a used one for a lot less, but then you have to assess the wear situation and whether the company or smith who made it will help you overhaul it for a reasonable price.
CZ Checkmate
Sweet gun at a little over $3k last time I checked. It will eat slide stops like any CZ, but I hear this is a pretty good gun from the factory that will run 9 major.
Tanfoglio open guns
Tanfo (imported by EAA) has an off-the-shelf open gun offering that is in the $2k price range (the Gold Team Eric). You can get it in 38 super or 9mm. Making major out of these with 9mm is reportedly challenging because they come with
12 popple holes in the barrel (in addition to the comp) - you need a huge amount of powder and gas to actually hit major with that much porting bleeding pressure. There are guys doing it, but that gun really only makes sense in 38 super. And the comp put onto a non-ported/poppled barrel isn't very effective by itself from what I have read/seen.
There may be a better solution that is
just becoming available. A guy (Durso/kneelingatlas) who has built a lot of Tanfo (and CZ) open guns has just come out with a Tanfo-compatible compensator that is effective enough not to need popple holes. There's an active thread or 2 on the Enos forum where it is being discussed (and many prior threads while he was developing it):
https://forums.brianenos.com/topic/266794-tanfo-9mm-major-open-gun-questions/ . This opens up the possibility of getting a Tanfo Limited ($1.1k), buying the appropriate replacement barrel, threading on the comp (probably $600-ish for those parts and the labor, unless you can do the labor yourself), and you're ready to stick on a red-dot.
With any Tanfo Open gun, lack of available big-stick 170mm mags has been a big issue, but MBX has some that
some can make work, and Taylor Freelance
just dropped a 170mm mag extension (total length, not the extension itself); I have one in the mail that may arrive today.
This approach is very interesting to me, as I've been using a Tanfoglio LTD in limited for the past 4 years. I know how those guns work, how to fix them, what breaks, how good the trigger can be, etc. They have approximately nothing in common with a Glock, except that, when everything is in spec, they run very reliably and are a lot less picky than most 2011's I see.
* ETA - mcb reminds me that technically one could shoot a 6-shot revolver using 9 major and get major scoring. Basically nobody shoots 6 shot revolvers in USPSA since they allowed minor-only 8-shot revolvers (with lots of 8-shot array/positions, this is very advantageous), so this is more academic than of any realistic consequence, but he's correct. Technically correct.... the best kind of correct.