On 6/29/2015 5:30 PM, Ethan McKinney wrote:

True, but when the western units went to the DS rounds, they also went
to a 120mm smooth bore.  No rifling, no spin.

US introduced 105mm (rifled) APFSDS in 1976. I believe that it simply didn't engage the rifling, although I know that some setups have use ball bearing to let let the round spin very little on its way down the barrel.

IIRC, the penetrator spun freely within the sabot which did interact with the rifling.  It worked, and was effective, but the smoothbore concept was much better.

--
Kurt Feltenberger
kurt@thepaw.org/kfeltenberger@yahoo.com
“Before today, I was scared to live, after today, I'm scared I'm not living enough." - Me