Here are the basics for the Oklahoma CCW:
You must be 23 years old.
You must take a training class (stupidest class I have ever taken).
You must fire your weapon at a target (no scoring involved, instructor discression).
If you use a derringer, the only thing you can carry is a derringer. If you use a revolver, you can carry a revolver or darringer. If you use a semi-automatic pistol, you can carry all 3.
I used a .22 semi-auto pistol for the test but carry either a .380 or a .45.
I have seen the requirements for the Texas CCP. Talk about a PITA, I don't think many people could pass this. If it were me, I'd get an Oklahoma address, get the Oklahoma one and move back to Texas. Gotta love reciprosity.