If you've seen the bug report I made, skip this whole bit

Whenever MK5 is called somewhere completly encased by blastproof blocks, such as concrete and etc, it errors badly and deletes everything in a circular radius. The picture above shows a comparison between a little boy, greg nuclear shells (both of which spawn their explosion above the concrete) , and a nuclear missile (spawned the blast within the concrete)

If I were to hazard a guess, the issue would be at the processing, since I checked ray hits using a debugger and they seemed to hit about where they meant to

Specifically the inChunk check, since the only chunk that errors is the chunk where mk5 was actually called at.
Here's a glitched chunk, made by completly encasing a nuclear charge in concrete

Another reason why its probably the inChunk check, is because when I removed it entirely for testing, the blast had the exact same shape, except it was all the chunks it affected

A temporary fix for the missiles would be to simply offset where the explosion is called up, proportional to how big the blast is, I found that 6 blocks up works for a 100 radius missile.

this guy goes into the negatives when processing the center chunk, causing the explosion rays to extend in the opposite direction