If done properly (port landing in grooves between rifling), the cyclic rate of the rifle is unaffected by gas port wear over the life of rifle due to bullet passing over it.
If done improperly (port landing on rifling instead of grooves), the bullet shear increases, thus increasing fouling.
Insas has a six groove barrel, compared to 4 groove barrel of AKM. This would require greater precision from the manufacturer.
Port erosion can be dealt with the gas regulator. Don't really know why this is being done.
The gas block is angled typically indicates that the hole in the barrrel would also be angled, but then, this is not necessarily or always the case.
One has to see the barrel with the gas block removed to see what it looks like.
For general interest, an angled hole looks like this:
It is not uncommon to have an angled gas block with perpendicular hole in the barrel. Many aftermarket repairs of the Kalashnikov have parts from different sources, say the barrel from Romania and the gas block from Yugoslavia. As long as the holes line up, it should work fine.
Regarding bullet shear if the drill lands in the rifling, many DYI discussion fora talk about drilling holes as an aftermarket activity. Some say the first time a bullet is fired, it clear out any obstruction and the subsequent bullets will pass through just fine, but then, one couldn't be too sure.
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My speculation is that this is a cost saving measure. The barrel has been slightly elongated from the older INSAS, and uses the same gas pipe. So, instead of using the straight block, they are using the angled block so that the angled block can reach up to the hole in the barrel, which has moved forward. Now, the question is why didn't they just drill the hole closer to so that the old perpendicular block used in the old INSAS could be used? One possible answer is, those few extra millimeters of barrel will add to the thrust and thus increase range of the bullet, before the gas gets sapped into the gas block. Anyway, this is just speculation.
