Problem:
The weapons in arma reforger some weapons act as bullet shields.
This feature is a gimmick and is unreasonable and does not fit in with gameplay.

Solution:
Let modders edit the .xob files OR, override gamemat files,
which would provide many ways to tackle this problem and
any other future problems similar to this.

It would in general be really cool to edit / override bits of XOB data or override gamemat files.

Back to the problem of weapons acting as bullet deflectors:

Weapons which use the weapon_metal.gamemat are often acting as bullet deflectors in gameplay.

The problem is that this is from a gameplay standpoint this is a weird gimmick,
which is unbalanced and doesn't fit with the rest of the gameplay.
also this can cause confusion and make players think there's something wrong with hit detection or net code or anything else
As something like this is not expected behavior.

From a realism standpoint, this does not make much sense as well.
It would only make sense if the guns would break in the game and
after deflecting 1-2 rounds, the gun would degrade and stop blocking bullets.
However, currently it seems like the guns can deflect as many bullets as the deflection calculation decides.

https://youtu.be/m1P0dP3M7fE?t=420
This video demonstrates how weapons can protect from some damage,
they are not reliable as bullet deflectors, such as is the case in arma reforger right now.