A standard twist drill, silver soldered on to an extension will work just fine but you have to withdraw the drill to clean frequently. In a 22 bore, a 5/16 drill can go no more than 1/2 inch before it should be withdrawn and cleaned. With a twist drill, it has to be pushed a bit to center it up in an existing hole. Drill too slow, and it will wander. The shank on the drill also acts to center the drill from the rear. I have drilled a 1/2 inch hole through 54 inches of hydraulic rod by drilling halfway from each end. Where the holes met was within .015" of being aligned. A lot of work though; it took close to two hours. When I was extending a bit for this purpose, I check the bit for straightness ahead of time. If the drill bit wasn't straight, I didn't use it.
One of the big advantages of the piloted drills sold for the purpose is that the drill does a good job of clearing chips. The flexibilty of the bit is what makes the pilot mandatory. GD