Best way to level weapons?

[(XBOX)Epic x B1ade]

I currently have Neptune unlocked (about halfway through) and I run Seimeni on Ceres to level weapons (after uneqipping other weapons). Is there any other ways I can level up faster besides using boosters?

[ashrah]

do spy missions on ceres u get lot xp...solo.....makes some coffee good music.. and u max wepon just like that

[SpeedOfLightPuncher]

if you completed second dream (idk how the progression goes) stofler is really good 

if you didn't, just run Draco (the survival) with randoms or friends, people say it's pretty good 

[(PSN)hirprirode]

Pluto oceanum spy mission solo is easy and give a lot xp if you hack undetected

[(XBOX)Epic x B1ade]

Thanks for the suggestions guys. I'll give them a run if I don't keep getting the "account could not be updated" error at the mission rewards screen time and time again. Had it 6+ times in the past 3 days!

[aligatorno]

Oceanum is great for leveling weapons, you can max a weapon in about 8-9 runs. What I would also recommend, if it's a melee weapon, take a stealth frame like or someone that can open up finishers undetected [ Equinox's Sleep / Excalibur's Blind and so on] and do a grineer exterminate. If you keep up the combo long enough, you can even max out a weapon in one run. 

[DelegadoZero]

Stealth Run
Example : Saturn exterminate 20-22 ( i just dont trust machete that's why saturn) or something like that
1 mission Machete  Rank 5 > 30(with booster but not necessary )  - 5.5k focus
https://postimg.org/image/tyceq8sir/
 

Also : 23k simaris 8k syndicate
https://postimg.org/image/pdq8bb8tf/