Noticed that on the Sierra SIG V-Crown 9mm 124 & 125gr bullets the can is at different points as well as the differing profiles... Since they are for semi-automatic calibers I'd believe the concept stated above probably applies...?
Yes, that's one that has a faux cannelure. Can't remember where I read it but it's for core retention & to control expansion.
Another is (was) Hornady's 45 caliber 200 & 225gr FTX bullets. Back in 2013 I bought a box of the 225gr FTX bullets specifically to try the "dual cannelures" and seat them to different depths but still be able to give them a roll crimp.
The Hornady literature at the time showed the "two cannelures" as did the picture on the box of bullets I purchased.
I was surprised to find the bullets in the box only had one cannelure so I emailed Hornady to get an answer on the difference.
They said, "This bullet actually has a single cannelure for loading. The small cannelure close to the base of the bullet is not intended for loading, it is there to aid in core retention and to put the top crimping cannelure on the bullet. We have recently developed a process to do this without the need for the bottom one."
You can see the different in their catalog pictures from 2013 & 2022 below.
Hornady's 45 caliber 300gr XTP does have two crimping cannelures to give you two different seating depths, & COAL", depending what cartridge & firearm you're loading it for.
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