Necromunda: Underhive Wars

Rank VI Weapons should not be a problem, you'll get these from enemies starting at around enemy gang rank 4000. You only need 1 two handed weapon for this and they are fairly common. You can also, rarely, buy them from the shop or get them in Rank 10 reward / gambling chests.

Armour will be the main problem, you can only get these from rank 10 gambling chests available on deadly operations and, rarely, fore sale in the shop and in loot drops in mission. You can never get armour from downed enemy fighters.

Completing Deadly Operations shouldn't be an issue given how poor the AI is so get onto these as soon as you can (with Rank 5 weapons and Armour, you can get these from influence rewards quickly), you can have unlimited funds by hiring and fring leaders and selling their equipment, discounts on hiring from the training hall and bonuses from influence, for sale price at the shop and another hiring discount, will speed this up.

With funds you can then hire Champion Gangers (2800 XP, puts them at level IX with full skills). In this way you can be completing deadly operations from your 2nd operation, using the first just to build some influence.

When in deadly a Op make sure to buy gambling chests and any rank VI Armour in the shop when available (every 3 shifts / missions it refreshes), it should only take one or two complete deadly operations to unlock this achievement. The Epic Higher roller bonus can also add up to 6 (for 8-9 total) each shop refresh which will greatly speed this up.

When buying gambling chests and not getting a Rank VI item you need if you dashboard and reload before exiting the shop menu you will be back as you were before you purchased. Keep reloading until you get one for an empty slot.

As a note: If you use a Deadeye you need one less piece as their right shoulder is locked to use the grapple and so you don't need a VI piece for this to fully equip them,