I also need to know how strong it is, as in the objects it can penetrate and the effects it could have on a human if it were hit with one bullet. Simple stuff. Oh right, and the amount of ammunition it carries with it before it needs some reloading. If this is too strong, or powerful, I suggest having a very time consuming way of reloading to kind of balance it out.
The horse, it needs more detail. Buki Buki no mi, ok great; if anyone read this they'd have to either guess or get off their asses and look for the ability of the fruit (or know what it is irl). Assuming I don't now what this fruit is, (which I don't) try and add the effects of it, as well as what the effect is on your horse. A horse with the human human fruit can talk, fight, and look different. Try and be specific on the abilities that the fruit gives the horse specifically. I also need to know how much the horse can carry before it, y'know, can't carry.