It is true that that website did claim it was: " The barrel is steel and button rifled using a 1-10" right hand twist. " I have read that some other american manufactures use a slower twist. The faster 1 in ten I recall was used in the original luger. It is quite a fast twist for such a short pistol bullet, but perhaps the renown penetration of the 9 mm pistol round is due in part to the rapid twist. A 1 in 10 twist is sufficient to stabilize a 220 grain 30-06 round so in luger that might exceed 300 grains or more in weight.