Ok, my previous deep drilling operations went off pretty well. Carbide
3 flute drills worse used on a couple of them. One to start holes for a hand ground split point, and the smaller hole with just a carbide jobber drill. Both actually met up in the middle close enough. One for a hinge pin and the smaller one for an injection cavity feature. They worked. Didn't actually do any gun drilling.Now I am looking at an application that will need to drill straight (size is not highly critical), for from 20 to 28 inches for a water jacket.
The only machine i have I think would be suitable for it is the 14x40 engine lathe. Throwing a 20x30 inch piece of plate on the chuck is obviously not the answer. LOL. I was thinking to use some sort of tool holder in the spindle, and make a mount and support for the plate on the carriage. After doing a bit of reading gun drilling does not just use hydraulic pressurized oil. It is also done with pneumatic air mist under pressure. Now the trick I think is to figure out how to pressurize a spinning gun drill inside a lathe spindle. I have some ideas, but they are kind of vague at this point.
The thought of buying and setting up a dedicated machine down the road is not out of the question. Right now I am looking for the shade tree get it done short term solution.