Materials should still has a limit of 300 on each player, but one can visit a station to withdraw more if they have the access right. And no guild in the right mind will open it up to just anyone, so people still have to earn it.
Deflection. That's not addressing the point.
The point I made:
The materials one for example. Player A is mining materials on a planet. Player B benefits from those materials, on account of being in the same guild. Player B thusly has access to the extra damaging ammunition, without necessarily having to collect any materials themselves. This puts them in a somewhat better position than Player C, who mines their own ammunition.
So those things have to be thought about very carefully.
As implemented right now, the materials are hen's teeth, and involve a fair amount of prospecting on multiple stellar bodies. It would seem that the intention is that the bonus ammunition is supposed to be very, very scarce, and best employed at a key moment to get the jump on someone, or to blat a target that is attempting to charge FSD.
If you can share materials in a guild then Player A mines materials, is in the same guild as Player B. Player B can withdraw materials, to make the +X%damage ammunition.
Whereas Player C mines their own materials.
So, allowing materials sharing within a guild, tends to promote the routine use of the +X% damage ammunitions, and makes guild effort more powerful than non-guild effort by a substantial margin.
Proliferation of the bonus ammunition affects the meta-game in many ways, for example:
It increases the size of ship that could be shot down with a single clip of ammunition - affecting how viable smaller ships are in pvp, who might be able to escape or evade while the other ship is reloading.
It alters the effective difference between weapon types - Lasers have no bonuses from synthesis, so bonus ammunition proliferation is effectively a nerf to lasers.
There are also social effects, e.g. there are some players, whose reaction times are worse than others, who, rather than being an inaccurate extra gun in a combat situation, would provide more benefit to the group as a whole by mining rocks on planets. They might feel pressured into doing that, instead of something else that they might enjoy more, even if they're not very good at it.
Allowing players to sell materials on the market somehow, and for other players to buy materials, would mean that non-guild players aren't necessarily at a disadvantage compared to guild players, but that would still mean that the bonus ammunition is a lot more common than before, affecting the meta-game. Which is a change from what appears to be the intention.
So being able to share materials in a guild is not a simple thing.
And that's why those things have to be thought about very, very carefully. Unintended consequences and all that.