Originally Posted by JTJ
It varies with the bullet design. I have found that XTP's have a good ratio. I carry a 380 at times and the XTP does not expand as much as some so it penetrates better in the 380. Others will not expand at all and over penetrate. I was ready to go to hardball when I found the XTP info.
I often use 180 gr. XTPs in my 4" .357 Mag. This is not a snub nose gun to be sure and, you'd probably never shoot 180 gr. slugs from a snub nose gun but, I can tell you that the XTPs do not often give much expansion at all. Usually they perform much more like super-hard cast bullets than jacketed hollow points, i.e.. more penetration.
This is not all bad. Wyoming requires that hunting bullets be "expanding" so; that rules out the hard cast bullets. The XTPs, however, because they are JHPs, qualify as "expanding" and yet offer penetration on par with the unacceptable cast bullets. This can be a very good thing if your trying to punch through heavy bone.
The very best expanding bullet I've found for the .357 is the 180 gr. Nosler Partition Gold HG. This bad boy has a hollow point like an ash tray and opens up on impact wider than anything I've ever seen. Unfortunately, it was discontinued a few years ago and I am now down to my very last box. It's almost enough to make a man cry...
None of this, of course has anything to do with bullet performance from a lightweight carry gun except that XTPs do come in lighter, more snub-friendly sized slugs. So if penetration is your goal, they may be worth a serious look.