[spxyu02]

Nice guide, I was using a similar method and this video helped me refine my route.

HOWEVER, I just fulfilled all the requirements and the achievement didn't pop. Anyone have a solution or similar experience. I'm gonna paste here what I commented over at TA:

I had it glitch on me solo/easy (local) also. Bought quick revive [1] & speed cola [2], went down, revived, bought who's who [3], other building and bought mule kick [4], jug [5], double tap [6] and finally pack-a-punched the ak74u from the wall [7]. I also built the trample steam in the early rounds to watch my back, if that means anything.

Locations (if those matter) were:
[1] Quick Revive - normal place
[2] Speed Cola - Other elevator that goes to top floor of spawn tower
[3] Who's Who - Last elevator in spawn tower, tops out at PDW floor
[4] Mule Kick - Power Room elevator, right hand shaft
[5] Juggernog - Power tower shaft that doesn't go all the way to the top
[6] Double Tap - Power Room elevator, left hand shaft
[7] PaP - Power tower final shaft, only goes to roof and floor just below

I'm going to give it another go on a solo custom game, instead of choosing "Local" from the main zombies menu.

UPDATE: Just got it in a Solo custom game on Easy (set privacy to invite only). Used the same strategy as before, PaP'd my starting M1911 to Mustang & Sally since I was able to do this by Round 8 with a beastly 2x streak training zombies in the bottom of the upside-down tower after getting my spawn tower perks and before getting jug/mule/double/PaP. So the main differences were Public (custom/invite-only) instead of Local (still on easy), and I PaP'd my starting pistol, and the PaP was not the final perk (double tap was last, in that 2-floor only elevator that paints you into a corner).

Good luck guys!

PS The final thing I did differently on my successful attempt was to not pick up any parts whatsoever. On my first attempt I had built the trample steam, but on my successful attempt I didn't pick up any keys or building pieces.