What HP rounds have you tried feeding it? The CCI MiniMag 40 Gr. round nose has no huge difference in profile to the CCI MiniMag 36 Gr. HP. This is an interesting topic and it has sparked my interest. I grabbed a few rounds I have lying around and took a comparison picture of them. From left to right, Winchester 36 Gr. HP (bulk box ammo), CCI 40 Gr. Round Nose, CCI 36 Gr. HP and then Remington CBEE 33 Gr. truncated cone hollow points (same TC design as the Remington Yellow Jackets with the addition of pre-stressed HP - the CBEE's won't load in a semi-auto but it's because they're underpowered). A LOT of people have trouble with the truncated cone design loading properly in different guns. The most ammo complaints I've heard about in a semi-auto are the Remington Yellow Jacket because of it's TC design. There's little difference in the CCI HP and Round Nose designs. Try the CCI HPs if you haven't already since they're easier to find than the CCI round nose rounds. pinecone is right. CCI still makes some good round nose ammo.
By the way, you mentioned that the newer HP ammo was 'longer'. The only HP I have seen that might give the perception that it is longer is the CCI Stinger round since it has a longer case but shorter projectile. Otherwise HP rounds are a big shorter. I'd be curious to hear what you're trying to feed that gun.