I have two HKS (22-HR) 9-shot speed loaders for my H&R 999 Sportsman. They align and drop cartridges into my 999's cylinder just fine.
Of course, once the chambers in the cylinder get too dirty, cartridges won't drop in fully.
One thing I've noticed is that older revolvers seem to have better finished chambers than the new revolvers I've purchased in the last 10 years. All the later made revolvers have had tighter, tool marked, un-polished chambers. While anything I bought that was made earlier, the chambers in the cylinders were better finished. Especially noticeable in the rimfire revolvers I've bought.