Don't know if a factory sporter barrel has enough meat to thread, will have to get your calipers on it.
As for the twist, it isn't about bullet weight; it's about bullet length.
Google: "JBM Stability Calculator" You can look-up bullet lengths and imput them into the stability calc to see if you will have a prayer in stabilizing them.
The next step is to not over-spin things. MV*720/Twist = RPM Sierra has the highest 22-cal RPM limit in their Blitz line, or approx. 320,000 RPM. Hornady runs approx. 290,000 RPM. Barrel smoothness and actual twist rate dependant of course.
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