Re: help on rifling twist
I have never had a problem stabilizing any bullet up to 140 gr in a 1-9 twist barrel chambered in my 6.5mm Allen Xpress which is based on the 300 Dakota parent case. Slightly larger but still in the same performance class.
I would probably still recommend the 1-9 twist just so you were not limited to the 120 gr bullets. Who knows there may come a situation where a 140 gr bullet would be a better choice. If you have a 1-9, your set, if you have a 1-10, stuck with the 120s for the most part.
The velocity difference between a 9 and 10 twist would not be worth trying to figure, extremely low if any.
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