Being a gunsmith doesn't mean just putting a gun together from parts. Putting it back together after stripping it to parts is the same skill as taking it apart in the first place. Also, it's important to note that field stripping is different from stripping a gun down to its nuts and bolts. Field stripping is usually a simple process, that can be done without tools, or, at most, with a limited number of tools and that is done just to do regular maintenance or fix easy to fix issues such as jams and such. Taking a gun apart completely is more complicated and will, most of the time, require tools. The main skill in field stripping is to be able to do it quick, without the need to understand that much about how the gun functions.
On the other hand, a gunsmith can build a gun not just from parts, but from raw materials because of his understanding of its functioning principles and design principles. The gunsmith is to somebody who field strips a gun like the architect and structural engineer together are to the common bricklayer.
If you dissemble a gun and you don't know what you're doing, you may lose parts (pins, springs etc) or damage them (some high end optics). You can install a scope badly and then wonder why the fuck it's not holding zero correctly.
You're
really missing the point of the argument. The actions are so similar in scope that there is no reason for them to not be the same skill. You argue that Field Stripping is a simple process done without necessarily understanding the gun's functionality while a Gunsmith fully understands a firearm, could build one from scratch and is the structural engineer of ranged death. So explain to me why a Gunsmith can't Field Strip a firearm? This is the same basic argument as with Field Medic and Surgeon.
Also, if I need Field Stripping for regular maintenance, fixing jams and such, why can my party of Rangers without a Field Stripper use aged, prewar firearms in the
field desert for extensive periods of time without worrying about a jam? Why don't I need training to load or operate a firearm at all? I have never handled one in real life and probably couldn't load an SMG properly, yet Ralphie can with no skill investment.
To the people who are adamantly defending having these multiple skills, do you think that some other skills should be split into different abilities? The most obvious example that comes to mind is Computer Tech. Do you really think that you should need different skillsets for unlocking loot containers or healing party members but everything done on a computer is okay to fall under one catagory? My wife has an IT degree from one of the better schools in the USA and is an excellent programmer but she can't fix her PC hardware, while I, an uneducated gamer who loves computers as a hobby, is able to.
Why do I need 2 skills to move a stock from one gun to another but someone half as skilled (say a level 4 vs a level 8 Ranger) could handle all aspects of Computer Tech with equal proficiency? Theoretically, Computer Tech will cover repairing computers, taking apart computers and everything that can be done with a working computer, roughly analogous to Gunsmithing, Field Stripping and one of the weapon proficiencies all rolled into a single skill.
Lastly, Safe Cracking is only an issue for some of you because there are so many safes in the game. Replace them with lockboxes, remove the skill and we're good to go. Safes are typically opened in RPGs without a skill anyway, as the player discovers the combination or uses something like Perception to hear the clicks, I
really don't want to continue arguing how hard it is to crack a safe, but I'm fairly certain both methods were used well in Fallout 2 (Raider base south of Vault City).