Semi-jacketed are that way so that the nose area is softer and hence it starts to collapse at lower speeds than a fully jacketed slug. The part of the SJHP slug that touches the gun is jacketed, so there's no problem there - the gun can't tell the difference between full jacket and semi.
BUT: most SJHP designs are out-dated, esp. in 38. It turns out it's better to go full jacket and run a big hollowpoint cavity in 38Spl. Winchester pioneered this with the 130gr "Supreme" 38+P and then Speer took the concept to it's ultimate in their 135gr 38+P Gold Dot. If you can't shoot plain lead 158gr hollowpoints then the Speer 135 is the ultimate. If you can't find that, the Winchester 130 ain't bad or the Speer 125gr Gold Dot "big cavity design" in 38+P. These beat ALL 38Spl or 38+P SJHP designs.
Sidenote: the only SJHP rounds that still get respect are in higher-speed calibers like the 357. They're still considered "old school" but I was excited to score a 50-box of the Remington 125gr classic 357 SJHP a few days ago. They may be stone-axe primitive but doing well over 1,400fps they work REAL well (and have a good record for expansion).
