While not a " 640 " per say, I do like my SAECO # 353 HP that I had Buckshot HP for me. Mine is a double cav.. The mold cavity that was not HP'd cast a solid at 180 grs. My HP version cast at 168 grs. with a generous HP cavity. I've shot this bullet into wet sand and found perfectly mushroomed bullets .700 " in diameter.
My HP pin goes all the way down to the crimp ring on this bullet.
Extremely accurate from my 38 Spec. Marlin 1894 CBC and shoots real good from my 358 Win. I'll include a target ( below ) shot with my 358 Win. , range was 50 yards , 5 shots, with the HP version of the bullet, load was 10.8 grs. of Russian Unique.
Considering the increased cost of g/c's , this bullet has a lot of potential in both full power pistol and reduced .35 cal. rifle loads .
If you have a SAECO # 353, you might want to consider sending it to Erik as I believe that Buckshot ( Rick Tunnel ) is no longer hp'ing bullet moulds .
I'm glad that I have mine, it is a KEEPER ! !
The Hp's that you see below are accurate and deadly ! !