Air Force doesn’t make a Texan model in .25 caliber. They make them in .257, .308, .357, and .457.
The whole purpose of the Texan platform is for hunting. You’re switching from pellets to heavier slugs at high velocities. You’re also utilizing barrels that have no choke and twist rates that utilize the specific diameter and weight of the projectile. If you want to shoot slugs from your stock Condor, you can indeed do it. But to get them to perform to a level beyond just a reasonable measure of accuracy will require modifications. The biggest of which will be a new barrel with a faster twist. The stock Lothar-Walther barrels in .25, .22, .20, and .177 all utilize a twist of 1:17.7. That’s 1 revolution in 17.7 inches. The longer the barrel, the more power the gun is capable of generating. That’s why the standard Condor with the 24″ barrel is capable of achieving 80-100 FPS than it’s SS counterpart with an 18″ barrel. But LW uses middle of the road twists on their barrels. In .25 or smaller they focused in on pellets primarily. Slugs are a secondary, less important option. The 1:17.7 twist is great for pellets but too slow for slugs to be pinpoint accurate. The twist is just a little too slow for the projectiles to achieve adequate gyroscopic stability.
But if you’re interested in converting your AF rifle in any of the smaller calibers to a slug slinging beast, then I know a guy in Russia who will make a custom, carbon fiber wrapped, polygon barrel in any length and in an assortment of twist rates. And believe it or not, he can make it and ship it for $40 cheaper than it cost you to buy a new LW barrel from anyone here in the USA. My cost out the door was $185. That included EVERYTHING.
There are the recommended twists for the smaller calibers:
.22 is 1:16
.25 is 1:14
Not sure about .177. I don’t know of anyone who’s tried to switch their .177 rifle to shoot slugs. But I would imagine you would need at 1:14 twist or faster to stabilize it, because the .177 projectile would have to be 2x’s longer than a pellet in the same caliber.