I Primarily carry an Xcarry and have been training with it. Sometimes when I do a mag change the slide drops, sometimes not. Is there a way to tune it so the slide always drops and/or drops without having to slam the mag in?

It's not supposed to do that. Either the slide release isn't fully engaged, or it's worn, allowing that to happen.

The slide of an autoloading pistol will release and close when a magazine is seated forcefully because inertia tends to keep the slide stationary as the frame (or grip module of the P320) is driven forward. That removes pressure on the slide catch lever and releases the slide.
That happens very commonly with Glocks, and in my experience it’s more likely to occur with a P320 than, for example, a Classic line SIG.

The variables are the weight of the slide and frame or grip module, and the strength of the recoil spring. The greater the difference in weight between the grip and slide, the easier it is to drive the grip forward as the slide remains in place. The less powerful the recoil spring, also the easier it is to drive the grip forward and not have the slide follow. That probably makes it more likely with a 9mm P320 than a 357/40 pistol, but the latter guns have heavier slides, so that might partially offset the spring power.

Another variable is how the pistol is held as the magazine is seated. If the force of the seating is parallel to the magazine well, that doesn’t drive the grip forward, and it’s unlikely to release the slide. If the force is more at a forward angle to the magazine well, that makes it more likely to release the slide. And of course the last variable is how forcefully the magazine is seated; the more force, the more likely to release the slide.

As for “tuning,” I can’t think of any good way to make it more likely to occur. Reducing the power of the recoil spring would help, perhaps, but could cause problems with reliability or durability. It might be possible to modify the slide engagement tab of the slide catch lever so that it doesn’t have to move as far to release the slide, but that’s not something I’d do myself. Do it wrong, and it will prevent the SCL from holding the slide open with an empty magazine.

If I believed having the slide release whenever I seated a magazine was critical, I’d work on my technique. As I explained, the force used to seat the magazine and the angle at which it’s directed against the gun affect whether it occurs. When it happens to me, I let it happen; when it doesn’t, I grab and pull the slide to release it and carry on. The time difference between the two is no more than a fraction of a second.

Moreover, I believe it’s a bad idea to expect it to happen. I have seen many Glock shooters who are accustomed to its occurring hesitate when they’re expecting it and it doesn’t. I take advantage of when it happens to me, but I also assume that it won’t.

I have seen pistols that will drop the slide when the user rams the magazine in place. Unfortunately, the slide dropped when they struggled getting the magazine in the well, and was closed by the time the magazine was seated. It all happened quickly. They lined up and squeezed, and heard a click.

Luckily the steel didn't shoot back. It was just a dumb target.

If they'd done that in a gunfight, they'd have been dead.

Hard lesson to learn.