check the serial number--if this is one of the 624s made in the early-mid Eighties, it may be subject to a recall (by S&W) to confirm it has a good cylinder. See the S&W Forum for a complete discussion. Really--do this; it's important information.
I have a 4" 624 from this era, and had it checked by S&W (it's a free service, including shipping). The 3" I just sold, although it's a wonderful N Frame--I just couldn't shoot it. (Besides, I had to pay for my Night Guard 396)
Get that sorted out, and then get issues 236 and 260 of Handloader. Issue 236 is the comprehensive resource for shooting .44 S&W Spl past the SAAMI 15,500 mark, and 260 is an "update."
They describe level I (SAAMI), level II (to 22,000), and level III (25,000) ballistics. I have no interest in level III (aging hands), but the thought of a 200-gr running at 1200 FPS does get me salivating a bit--or a 250 at 1000 or better... you get the idea.
Jim H.