So this Mekboy special Talent seems a little underpowered to me. For 500XP I'd expect a bit more than just having Reliable weapons and temporarily improving weapons.

I figured a Mekboy worth his teef will have made himself Best-Quality weapons already, and the Reliable trait of the gunz don't apply if he makes gunz for his humie friends.

So what am I missing?

Orks... making BEST quality weapons? For humiez? I have a problem with the premise to this scenario.

One option though: Your Dynasty has challenged another Rogue Trader to some random pointless challenge - the best kind! You have managed to gain access to the enemy Trader's armoury, and "upgrade" all of his weapons, while the Seneschal who came with you walks around unloading all of the weapons.

Kinda niche, but I think if you can do the things that you've described then you probably wouldn't get a lot out of this talent.

The Reliable trait doesn't apply if he makes weapons for his Ork friends either. It applies to Ork-made weapons he uses, regardless of whether they were made by him.

Additionally, Ork-made weapons have their own Craftsmanship modifiers, and none of those include Reliable or immunity to jamming.

In my experience there tends to be two types of gun Meks.

One is the type that tends to have one weapon that they constantly tinker with in an effort to make it the most powerful weapon in the history of things that kill and maim. This archetype goes back all the way to when they were called Mekaniaks and one wielded a kustomized heavy Plasma Gun named Sally. This type of mek probably won't get a huge benefit from the Worky Gubbinz talent.

The other type of Mek wants all the guns. The fact that there might be a type of gun he hasn't used drives him to distraction. The quality of the gun is largely inconsequential as the second it stops firing he will discard it and start shooting a different gun. These Meks tend to have a gun in each hand, a gun in the hand of every nearby gretchin and some sort of shoulder harness to enable 'ands free dakka. They will constantly bemoan the fact that they have only two hands to shoot with. Rather than upgrading existing weapons these Meks will spend their time creating new weapons attempting to ensure that like a Swiss army knife they always have the right tool for the job.

Given that the easiest way to ensure rapid production of guns regardless of component availability is to skimp on quality this style of Mek is likely to see the most benefit from the Worky Gubbinz talent.

Also if we look at the talent itself

Prerequisites: Ork, Tech-Use +10, Willpower 30+

The Ork has an innate and instinctive skill with machinery, allowing him to perform feats of engineering that defy logic, cobbling together random lumps of wrecked technology and scrap metal into something bizarre and startlingly effective. Orks with this talent gain the following benefits:

An Ork with this talent counts all Ork-made weapons as Reliable—his greater understanding of them allows him to use the weapons more effectively than other Orks.

An Ork with this talent may attempt a Tech-Use Test to quickly “kustomise” any device he comes across, whether it needs it or not. With weapons, this takes a number of minutes equal to the number of half actions the gun normally takes to reload. If the test is successful, then the gun’s craftsmanship improves by one step until the next time it needs to be reloaded, at which point it breaks and will need to be repaired. If the Ork “kustomises” another hand-held device or piece of gear, all tests to use the object gain a +5 bonus for a number of hours equal to the Ork’s Willpower Bonus, at which point it will cease functioning. The GM can devise alternative effects for a Mekboy’s “kustomisations.” In all cases, if the test is failed, then the device breaks and will not work until repaired fully.

The area I've bolded out seems to suggest that perhaps discussions with your GM about other potential effects for Kustomizations might be worthwhile. Personally I'd find it acceptable for a Mek faced with an enemy that had a vulnerability to a specific type of damage (say energy damage) to modify his weapons on the fly to cause energy damage until the next reload.

Thinking on this further I'm quite enamoured with the concept of a swiss army gun.

The Mek might have his old faithful a kustomized shoota (reload is a half action) that can be configured for whatever he needs.

Need to climb a wall? One tech use test and now it's a grappling gun.

Attacked by a hoard? Rearrange the gun a bit and now it's a flame thrower.

Found some grenades that you want to shoot? Tweak this, replace the barrel now instead of bullets it fires grenades.

Want to shoot those organ grinder rounds the Rogue Trader keeps bosting about? Just a minute of kustomizing and watch the carnage.

You'd need to talk with the GM about the guidelines to ensure some form of balance but as long as you're not going overboard it could work.

Yes, I did see that line, and started thinking about it.

I think this is a fun talent, but I don't think it's worth 500 XP. Not unless you get to do the things Mr. WeedyGrot suggests. That kind of versatility would definitely be worth it. It may even be a little too much...

A little thread-resurrection here...

How will this Talent affect Melee weapons?

The wording of the talent say he can improve the craftsmanship of weapons, but then goes on to specify durations in terms of reloads, which is only relevant for Ranged weapons. Other items are given a duration in hours, before the break.

Just how would an "improved" choppa break, and what is required to repair them? A normal tech-use test? A Trade (Armourer) test?

I'd assume a Trade (Armourer) test would be needed.

As far as I understand, Trade (Armourer) will let the tradesman improve craftsmanship of Arms and Armour, amongst other things.

But the Worky Gubbinz Talents does not require the Trade skill, and lets you improve things (such as weapons) using Tech-use. It also specifies that the "fix" is quite quick to apply, and has a limited duration.

Indeed that is why I'd go with Trade (Armourer) for weapon repairs because you're actually applying a permanent fix rather than overloading the chainsaw engine (or whatever) for a temporary boost in effectiveness.

Personally I would would let the Melee weapon work for a single combat. Or it gains a clip size and works until it has to be reloaded - depends on how the Mek want's to upgrade it. Gunblade Choppas don't seem out of line for a mek.

Good idea!

And while on the subject: "Until it needs to be repaired". Are there any rules for repairing broken weapons? It's handled by tech.use I think, but time and difficulty?

There are upgrades made especially for ork weapons in both ITS and Hostile Acquisitions. And I think there was a note that Ork Mekboy could use it quite well. So I see absolutely nothing wrong with upgrading weapons using that talent with this things and possibly some new ones you might come up with. It's just that it might turn out TOO good, heh.

As for broken weapons, there aren't many rules for broken weapons to begin with. Only for quality. Broken weapon happens only in special circumstances with abilities or just when GM says so. It's handled by Tech Use, but the time and difficulty you'd better set up yourself. Using crafting rules for reference.