I like the metal handguard but with the short barrel, it's kinda just floating inside without the cap. So I made this simple barrel centering ring that uses grub screws to hold it in place. I'll leave the purchase link to the grub screws I use. They have a rubber tip so that it will not scratch up your barrel.

The reason for that little opening is so that you don't have to remove your m-lock nuts to install the ring.

Don't over tighten! I strips very easily. Just need the rubber tip to be touching the barrel and that's it. It uses the M4 grub screws. I'm using the M4x5. You can go with slightly longer ones if you want.

Links:

https://www.aliexpress.com/item/1005001635015496.html?spm=a2g0o.order_list.order_list_main.74.60201802ve4GTK