Might not be the gun, might be your settings and I/m guessing you strained the primer when putting it into the siphon cup?
There may be something on the nozzle or fowling the nozzle, Also check air pressure and moisture in the air line you are using. If it is blowing out chunks them you need to use a strainer when pouring the paint/primer into the siphon cup. if its just splatter look what I mentioned, its throwing to much paint or the spray pattern isn't "clean" and the nozzle is fowled or defective.
Yup or it could be the viscosity is to high for the gun. For primer usually a 1.8 to 2.5 mm nozzle is used.
I use a Sharpe Finex 3000 for my topcoats as I'm a decent amateur paintr but the good painter use Iwata and other 500 t0 800 dollar guns. The finex is about $125.
I would recommend you spend a fair amount of time on youtube watching videos of the paint types you are trying to spray. They are pretty good on how to spray and also setup the gun.
For your first gun, Go to Harbor Freight and get one of their "better" gravity guns with a couple of tips and practice. They are decent guns to start with. If you do have $125 or so, try the Finex as the first one, it's a decent gun for the price. I'd stay away from the high priced one initially as that's a lot of money to muck up early.
