Warframe

Update 19.5 Scythe, Pole-arm and Staff Weapons List

Scythe
• Anku
• Caustacyst
• Ether Reaper
• Hate
• Reaper Prime

Pole-arm
• Kesheg
• Lesion
• Orthos
• Orthos Prime
• Serro
• Sydon
• Sydon Vaykor
• Tonbo

Staff
• Amphis
• Bo
• Bo Mk1
• Bo Prime
• Broken Scepter (Reward for completing The War Within)
• Tipedo

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Unlocking Weapons

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

There are quite a few of these weapons as Blueprints on the marketplace, like Orthos, Bo and Anku.

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

The Scythe Hate is acquired from defeating the Stalker.

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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.

If you wish you can start off with the MK1-Bo when you may pick your first Melee weapon.

On the Market you can also get the blueprint for in-game credits from the "Amphis" & regular "Bo", who are both Staffs. Also there is in the Melee blueprints the "Orthos", that is a Staff with a blade on each end.

This one unlocked when I got the MKI-Bo to 30. I assume this is a glitch. Someone else reported the same type of glitch with a different one (pistol) but I didn't have that happen with it so I imagine it's random when it occurs

What i did, and it's working is when you are close to level 30 with any weapon go to any mission and immediately, when you hit level 30 close game. Repeat that process 3 times and you will earn the achievement.

You can check the progress on the achievement tab to see if it works :).