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I was told that and N320 are basically same.
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They are not the same. The only thing these powders have in common is that they're fairly fast burning. However Titegroup is faster, somewhere between N310 and N320. Titegroup burns much hotter, is smokier, and is said to be temperature sensitive while N320 is not. N320 is a single base powder. Titegroup is a double base powder. They have completely different shapes - Titegroup is spherical, N320 extruded. They are manufactured by different companies in different areas of the earth and sell for different prices. Finally, the load data for these powders are
NOT interchangeable. When it comes to reloading, it's best to stick with the manufacturer's reloading data and reliable third party manuals.
On the original topic, a common source of keyholing comes from accidentally swagging lead bullets during the crimping operation. This of course will affect how it engages the rifling and stabilizes the bullet. Another common source is a really dirty (leaded) barrel where little rifling remains useable for engagement. Gas cutting with too small a bullet is also a major cause of keyholing, which tends to lead the barrel too, thus making the keyholing more common as the shooting session continues.