Sniper, some Norinco SKS were originally imported with a bayonet, some not or at least were not allowed to leave the import impoundment area with that bayonet attached. However, the one in question is being modified differently from the way it was legally imported. It will no longer be considered an "imported" SKS but a US manufactured.
Well, only if he does the 10 or less game, of course. And if he does, then import restrictions no longer apply. And there are no restrictions on bayonets on US made rifles that I'm aware of, either in federal law or Texas law. It's simply not an issue on US made rifles.
I may be wrong, but I believe there is a possibility it loses its imported status with the Federal protection granted that bayonet. Additionally, I know of no sporting event that might occur at the shooting range that includes the use of a bayonet. Thus, Texas may not agree one can attach a bayonet onto a US made rifle.
But again, there are no restrictions on bayonets in Texas. The only issue here is whether it's considered a "knife" that would be over the legal length. And since it's attached to a rifle and does not have the ability to be quickly removed and used by itself (unlike a typical rifle bayonet), I don't see how it could be classified as a knife. It is simply a blade that is part of the rifle. One doesn't need to prove there is a "sporting purpose" for a permanently mounted bayonet on a US made rifle any more than one would need to prove "sporting purpose" for any other feature.
I guess what I'm saying is that if the 10-or-less game is won, the rifle becomes legal to possess with such evil features. The folding bayonet is a part of the rifle, not a separate knife. As long as it remains attached to the rifle, I simply don't see how it could possibly be classified as an illegal knife, and therefore is not an issue.
I'm not a lawyer, nor do I play one on television. Just trying to apply common sense to it (which can be dangerous, I admit). But I'e never heard of anyone in Texas getting in trouble for an SKS bayonet or being charged with an "illegal knife".