Let's be honest, how many of you actively use things like the Concussion Railgun or the Xangi Xi Self-propelled Concussion Launcher?
I guess it won't be many if any at all, they usually just sit in a station and collect dust. The Conlauncher has a waiting time of an entire week just to make a new one and the Conrails require constant switching of stations to manufacture them.
Also the Conrails are 10k per shot, so it's 100k for a magazine of 10!!!

Many stations sell Conrails, for example Latos N-2 has 1003 Conrails but at the moment but no one can buy them. The Conlauncher isn't listed or sold anywhere.

My suggestion for these two is to let Conrails be bought by anyone that A) Completed the according mission tree and B) Has at least manufactured one Conrail. Also lower the price per shot to something reason, currently it's 10k per shot which is way too much. Maybe it could be 50 per shot (Sun Flares are 40 credits per shot).

As for the Xang Xi Self-propelled Concussion Launcher, it should also be manufactured at least once and the mission tree has to be completed. After that Xang Xi (and maybe Latos N-2) should sell it to players.

PS: If you know any other unloved dust collectors, please mention them in the comment section.

Concussion rails are easily acquired via a mission through nation space, or by manufacturing them.
The reload for concussion rails is pretty cheap. I suggest you do some trading, and you'll find out that credits are pretty easy to get in this game. Or manufacture yourself a capital ship, and get free reloads (or own conquerable station keys, and get free reloads at those stations).

I will say that the concussion rail gun needs a buff. The concussion effect needs to be increased. I think the refire rate should dropped to basically instant.

The Xang Xi Self-propelled Concussion Launcher is a special weapon that is supposed be rare. The one week cool down keeps it limited. If you want more in galaxy, then ask people to build them. In fact, haul everything that is needed for them to a station, and pay people to make them using your part stocks. There is only one item that is required to be fresh.

I use the Xang Xi Self-propelled Concussion Launcher in combat, as i like the the extra kick it gives in a tri rocket setup. But that is just me. They are just virtual widgets, so I use them and lose them without shedding tears.

The point is that they obviously don't get used very often so they should be able to get bought at stations, especially since many even have them listen and N-2 even has 1003 in stock. They could also get a buff but they need to be used in the first place. And 10k per shot for a total of 100k per weapon isn't cheap by any means. Sun flares which are probably better are 40c per shot.

I'm having a hard time understanding this concept. Can you please expand on this idea of yours?

In my opinion, something not being used often does not constitute a justification for it to be sold in the public marketplace. Some weapons should only be obtainable via third parties (or black markets). If you wish to use some rare items, you should need to go out of your way to track them down, and acquire them. This is part of the exploration of the galaxy. And if the weapons are too expensive at the time, then find a way to make funds.

-1, arguing the conc rail isn't used enought and therefore be a sold item is pointless. The point of it is to be a rare weapon. So let it stay rare