im realy curious because when ever i use it i cant kill anything with it and when i see other people use it its a monster i mean it doesnt even have any cannon rounds any advice?
Yep, and what others have told you explains why the P-51 is good, in the hands of some pilots, very good!
But what really makes it great is a combination of two other factors, the same factors that made it great in WWII.
The first is survivability! The P-51 is fast, and can extract you from situations that many other aircraft can't. For example, if you are in a fight and other enemy aircraft turn up, you can disengage, drag chasers away from the crowd and resume when it is 1v1 again. Or, if you are in a fight and begin to lose position, say the enemy aircraft is entering the control position, you can disengage, extend and re-engage from a neutral position. In that way you can even out maneuver Zekes by turning with them at high speed where your turn rate and radius will match theirs, and as soon as your speed drops, enter the "Disengage, extend, reverse, re-engage" cycle. It may sound boring, and if you are 1v1 with a better turning aircraft (and that includes most of them) it can become protracted, and that is where the second factor I mentioned comes in.
In real air combat it is very rare for anyone to fly as a single ship, that was a lesson learned very early in WWI. With a wingman, the strengths of the P-51 come into their own, and there is a synergy between that and the survivability factor I mentioned earlier. It is as if the qualities of the P-51 were designed with wingman tactics in mind. That also explains why most real fighters pilots in WWII on both sides wanted aircraft that had similar qualities to the P-51.
When the P-51 is flown in a two ship with a lead and wingman who know and understand wingman tactics and who have good communications and situational awareness the outcome can be stunning. Two P-51s can work enemy groups of up to 6 (that's 3-1 odds) superior aircraft and kill them all and if the situation becomes dangerous they can extend and use a rolling retreat. Again, if two P-51s are extending using the rolling retreat and being chased by LA7's, Spitfires, and other P-51s all acting as individuals, they can kill them all.
It is about team work and the synergy between wing tactics and the attributes and qualities of the P-51, each one on its own can make it good, when used together something almost magical happens... it becomes great!!
Unfortunately, if you don't take advantage of either factor, the P-51 can leave you wondering why it had the reputation it did. Now you know why.
Badboy