The threads are the exact same. A pinned barrel needs the exact same amount of torque as a non pinned barrel. The groove for the pin is generous enough that a pinned barrel that is not torqued up can be turned several degrees in each direction even with the pin installed. In reality the pin does nothing.
"Crush fit" is an incorrect term. If a barrel gets a restriction it is because it is was over torqued. But, a barrel must get properly torqued pinned or unpinned.
You can mount a non pinned barrel in a pinned frame by simply filing the notch in it.If both barrel and frame have clean threads it will spin right in until the rear shoulder meets the frame. Is shouldn't get hand tight hard until past 9 o'clock, although you can feel it start to drag a bit around 5 or 6. From 9+ to 12 you should use a frame wrench. It doesn't even need to be nearly as tight as a lug nut. My wrench only has a 14" handle.
I have over a dozen N frame barrels and as many K frame barrels and 6 or 8 J frame barrels. I have worked with pinned and un pinned frames. I can tell you for a FACT that if a barrel does not torque up in a pinned frame and you install the pin you can turn it back and forth by hand. Adjusting the rear shoulder on the frame correctly is 1000 times more important than the pin
Barrel restrictions. They are real. They are not that common. I check by finding the largest pin gauge that will start down a barrel. It should go from end to end smoothly. It is USUALLY .010 to .012 smaller than caliber A .442 pin will usually slide down a 45 barrel (.452)l, a .418 down a 44 barrel (.429)
