Excuse me. I've been off updating, hence the late reply!

By VRGun, do you mean ArcVR?
If so, we would appreciate it if you could confirm what ArcVR uses as its base.

I do mean ArcVR and I don't know why no one else is having this problem

The symptoms of the mags not fitting into the weapon vary depending on the ArcVR base. It is most likely a bug that occurs when multiple bases are enabled or when using old ArcVR weapons in NArcVR.

Currently, ArcVR weapons only work when held in the right hand. This is because ArcVR is fundamentally designed to be used with the right hand, and it takes time and skill to get it to grab with the left hand.
(In the meantime, there is an ArcVR for the left hand in production, but it is quite unstable. We do not recommend using it.
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2889152358)

If it's ok with you, try running it with only the mods in this collection enabled and the others disabled. (It is not necessary to uninstall the mods you are using, since the purpose is only to check the behavior and identify the symptoms.)
https://steamhost.cn/steamcommunity_com/workshop/filedetails/?id=2304296032

If it still occurs in that state, it is an unknown bug and we would be glad if you could let us know.

I've had a similar issue, where my gun doesn't accept mags directly from the mag pouch and the mags are way more wobbly than normal, and only mags picked up from the ground go into my arcvr weapons, cocking guns works as normal but the mags are just broken for me unless i drop them and pick them up again, then they work as normal.