Can we be sure that the massive and pointed blowing out of Kirks shirt that we have only rather recently seen is not fake and/or an image artifact? I‘m asking because in many of the initial videos I don‘t think I have seen such a massive and pointed blow out as that video is showing.
It was visible in the first, lower-quality video - it just wasn't as clear because of the blurriness.
Pretty sure it's impossible that a bullet that cleanly entered his neck would do that to a shirt. Bullets create little to no shockwave
They don't create a shockwave around them when they're flying through the air, but when they enter the body they create a pressure wave that causes a temporary wound cavity. Basically, the extreme pressure of the bullet entering and passing through tissue expands that tissue rapidly outward at a high speed. Hydrostatic shock may also play a role here, as the watery tissue rapidly expands with the wound cavity and can cause damage to more distant parts of the body, like the nervous system. Parts of the surface of the body might expand briefly and rapidly as a bullet passes through.
I only found one video with a ballistic dummy wearing any sort of clothing - but it is wearing a necklace of sorts. It's not directly analogous, for several reasons: this guy is using joke ammunition and shotguns, it's a dummy and not a real body, and the shots are to the chest, not neck. But it could still give some idea of the transfer of force involved when a stationary body is hit with a fast projectile. Look what happens to the ribbon and medallion when shot just above it, and then again just to the right (three timestamps
here,
here and
here). In the first shot, the whole ribbon gets pulled out in all directions, then the hanging medallion launches up over the head, the weak connections with the fabric of the cape break, and the medallion flies back over the left shoulder. In the second, the medallion launches straight up in front of the face and then gets pulled back down to the chest. In the third, it launches over the right shoulder.

One of the things Gary at PT is planning for his video is to get some ballistic dummies and try out various scenarios. Pretty sure he'll be using clothes and a necklace, so we should be able to get some data from that.
Whatever hit Kirk, it clearly had a lot of force judging by the reaction of his body, the contortions to his face, the flinging forward of the hair at his hairline. If it wasn't a .30-06, I think the most likely solution is that it just wasn't a .30-06. Either the Mauser was rechambered, or it wasn't the rifle used, or he was using an odd type of ammunition. All of those seem more likely than the microphone weapon, IMO. Like RedFox pointed out
Recoil (the launcher not being held steady) is the main thing that could debunk this theory. How do you launch a projectile with enough force without tearing out the shirt in the opposite direction direction?
Also considering that throughout the whole explosive event, the magnetic clip didn't even detach.