rocket delay differences

[MadBlaster]

I notice, for example, there is a longer time delay between when you are allowed to fire off the next round of rockets, comparing say ap hvar in the hellcat verses 4.5" rockets in the p38j. The hvar time penalty is short(good) and the 4.5" rockets are slow (bad). Are these time penalties realistic? If I attack a tank with the 4.5", it makes it much more difficult to ensure a hit on first pass because I only get one chance, but hvars I can fire a volley for much better odds and leave the target area without getting shot down. Why would it take longer to arm 4.5" rockets verses HVAR's?