I bought a Wingsung 699 recently from AliExpress because I wanted to try out a vacuum filler. Ink leaks from around the nib whenever I cap it, leading to ink getting on the grip. When I write, blobs of ink sometimes burp out onto the page. Is this typical for this brand? I have another no name Wingsung (I think it's actually a knockoff of the Hongdian dark forest) that has no issues.
I have two 699s and both are among my favorite Chinese pens. No leaking... You may have gotten a defective pen, unfortunately. Are you storing it with the blind cap screwed closed the whole way? If the blind cap is fully closed, the pen shouldn't be leaking at all...
The burping can happen with vac fillers as your hand's warmth causes air in the barrel to expand, pushing out the ink. Filling the pen up more fully may help - less air to expand. Are you writing with the blind cap open? This may help as there won't be a sealed off barrel in which the air can expand.
I'm storing it with the blind cap fully closed.
That's interesting that the hand warmth can cause burping when the blind cap is closed, I had thought that closing the cap would fully seal the ink reservoir from the nib.
It does, but there's still some ink in the little section between the feed & stopper, plus ink in the feed itself.