Warframe

It's not working this way (one sword which give you both achievements at same time) so I found another way. When you are close to level 30 with one sword go to any mission and immediately, when you hit level 30 close game. Repeat that process 5 times and you will earn achievement.

Update 19.5 Sword List

Weapons in brackets are Variations on that Sword, so there is a Skana, Skana Prime and Skana Prisma.

Swords
• Broken-War
• Cronus
• Dakra Prime
• Dark Sword
• Ether Sword
• Heat Sword
• Jaw Sword
• Mire
• Pangolin Sword
• Plasma Sword
• Skana (Prime, Prisma)

Dual Swords
• Dex Dakra
• Dual Cleavers (Prisma)
• Dual Ether
• Dual Heat Swords
• Dual Ichor
• Dual Kamas (Prime)
• Dual Raza
• Dual Skana
• Dual Zoren
• Nami Skyla
• Twin Basolk

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Unlocking Weapons

Mk.1 Weapons you can buy for Credits from the Marketplace and provide quick replacements.

A few swords are easily acquired through bosses or quests, these are;
Cronus Blueprint is found from Captain Vor on Mercury (level 1-6)
Heat Sword is from the Once Awake questline (level 7-12)
Broken-War is from the Second Dream questline (level 25-30)

A few more swords are acquired through Alerts, similar to Daggers are all exclusive Alert Rewards, keep an eye out as they pop up ingame or watch the Xbox Warframe Alerts Twitter feed. These include Dark Sword and Plasma Sword.

For all your other Sword needs, there are plenty of weapons on the Marketplace for one of the more populated weapon categories, making five Rank 30 weapons a simple thing.

Lot's of weapons require a Mastery Rank, but by leveling weapons you increase your Rank so this shouldn't be a problem, just make sure to Rank up regularly.
Check here for required Mastery Ranks or the Marketplace.

Prime Weapons require Void completion, often high level Survival/Defense 'Rotation C' drops. These are endgame. I use Primarch Prime Part Guide

Other weapons like Prisma, Vandal and Wraith Weapons are Limited Time exclusive weapons, some re-appear as Sortie or Week/end event rewards but some are gone, maybe for good. (Dex are Birthday weapons and they pop up once a year around April for free)

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Leveling weapons to Rank 30

The best way to level weapons is to play Survival or Defense missions and kill lots of enemies, then extract for the bonus exp, you'll get lots of weapon mastery whilst unlocking all worlds, doing alerts, unlocking other achievements and just playing the game. Remember to always swap for you next weapon and have one ready to swap.

Lots of Dark Sectors have Affinity bonus (+Shotgun), use a Warframe that supports you but doesn't really kill enemies so you rely on your weapons, being in a group spawns more enemies for more exp.

Elara on Jupiter is a great mission for Affinity, as the anti-moas spawn early and often, and they give a fair amount of affinity around 7-9x the exp of grunts.

It's my first guide in this site, so if you vote it negatively tell me why.

I think that this achievement is glitched, because I unlocked it reaching Rank 30 with a single Longsword, Skana exactly. You'll unlock Blade Mastery and Blade Proficiency (Reach Rank 30 with any single Longsword or Dual Short Blades) at the same time

At the moment (11 Sept) it's still possible to unlock it ;)

PS: Sorry for my bad english but I'm Italian

***This has been fixed in update 17****

There is apparently a glitch that happens in the game where if you click last mission results you can potentially get all the master achievements for that specific slot (ex. Primary, secondary or melee).

In order to get this glitch to work you have to finish a mission and ONLY when the weapon levels up from 29 to 30 in the end mission screen will this glitch work.

When this happens usually you should get the proficiency achievement if you have not gotten it and the mastery achievement for that specific weapon.

So when you return to your ship go to the back and equip a new weapon in the same slot that you just leveled up to 30 with the previous weapon. Now click the menu button and navigate to the last mission results option. When the screen pops up both achievements should pop for that weapon you just equipped. Rinse and repeat for the others you are missing in that category.

If you level up the weapon during the mission instead of at the end of the results screen this glitch will not work.

PS. If your weapons is a 29 and really close to leveling up or about half way. Go to a void mission and do one of those because it usually gives you a good amount of experience to be able to hit that 30 when the match ends.

Leave any comments on how this helps you and please if voted negative let me know. Good luck

Thanks LSK ArchDeific for proving this works