by Seismic Sam on Tue May 01, 2012 2:59 pm
55 reads and not one reply generally means "no". The 200 grain 40 caliber bullet was the original 10mm bullet, and it went out the barrel at 1200 FPS. The spec for the 40 is a 180 grain bullet at 980 FPS, while a 10mm will drive the same bullet at 1300 FPS. To maintain the OAL 0f a 40 round, you are going to have to seat a 200 grain bullet deeper, which means less free space in the case (if any), and that's going to jack the pressure through the roof. 40's have a nasty tendency to blow up if the bullet is seated too deep or sets back upon feeding, so you are playing with fire. If you don't have a chrono, there's no way you can safely work up a load, period. If you do, you are going to have to substantially cut the powder weight with 200 grain bullets and then work back up slowly, looking out for pressure signs on the case and primer, and any sudden spike in velocity of the rounds.