The advice above is all good, particularly the sharp tools part. You need them to be really sharp.
Here's a bit of additional advice:
Once you fix those inlets, and before you inlet anything else on the gun, practice on some scrap wood. Use maple if you can, or just get a scrap of good hard wood. Then practice inletting on it. You can try practice with scrap metal that you have lying around, or just get some from your local big-box store. It would be worth practicing inletting various thicknesses of metal as well - in other words, something thick as a trigger plate or tang, as well as something thinner like a .040 thick brass inlay.
As stated above, put a small amount of draft (or bevel) on the edges of the piece to be inlet. That will go a long way. And use way less inletting black.
I'm not great at inletting, and my first inlets looked pretty much like yours. A bit of practice really helps, and it's dirt cheap to practice with scrap, and time well invested.
Hope this helps,
Norm