Originally Posted by Larco
The MK319 BS is a size between the -3 and -4 rivets. I have seen them used in -4 holes with good results so If the hole is not oversized beyond that maybe ok. Try it on a sample and see. The 319 seems to fill a 1/8 inch hole ok from what I'v seen.
The ideal hole size for an MK319 is #34, so a #30 hole from a 426AD4 rivet is too big. If it was dimpled after drilling, or over sized from rivet removal, the situation would be even worse.
A flush Cherry rivet would be a better choice. Depending on the hole location, a CS4-4 might be acceptable.