We start at Cooke's Prison Break. At which point the Powder Gangers split into 3 factions: The NCRCF Powder Gang, The Bison Steve Escaped Convicts and The Vault 19 Powder Gang (originally simply 'Cooke's Faction' before reaching Vault 19).

We'll now go over all these factions, starting with the Bison Steve Escaped Convicts.

Leader: Escaped Convict Leader.

Several Unnamed Convicts (both called 'Escaped Convicts' and just 'Convicts')

This faction is unaffiliated with any other Powder Gang and does not have any implied affiliates who use Powder Gang Reputation.

Next we'll go over the Vault 19 Powder Gang

At Vault 19

Leader: Samuel Cooke

Opposition: Philip Lem

Several unnamed members labelled 'Escaped Convicts'

This group does not use Powder Ganger Reputation.

At Whittaker Farmstead

A few unnamed Powder Gangers who use Powder Ganger Reputation.

These gangers are explicitly linked to Samuel Cooke only in a cut note and by proximity to Vault 19.

Now we have the big one. The NCRCF Powder Gang. The main faction of Powder Gangers. All members use Powder Ganger Reputation.

At NCRCF

Leader: Eddie

Second in Command: Scrambler (could also be called 'Main Bodyguard' or maybe 'Enforcer')

"Doctor": Hannigan (6 months training as a medic)

Trader: Carter

Front Door Guard: Dawes

The NCRCF is also home to the unaffiliated non-member ex-inmate Meyers, at one point Meyers would've had his own small group of 'Deputies' if he was put in-charge of Primm (there is still some reference to them in dialogue).

Joe Cobb's Gang, which could also be called Joe Cobb's Crew.

Leader: Joe Cobb

5 other members

A raiding party of the NCRCF. They charge 'tolls' to travelers on I-15, some of Joe Cobb's gang (though Ringo says they attacked without warning).

Boxcars' Crew which could also be called 'The Nipton Crew'

Possible Leader: Boxcars

Other Members: Oliver Swanick, Legion Captives, Legion Crucified

The ill-fated Nipton party. Called 'my crew' by Boxcars. Use Powder Ganger Reputation.

Tricked into a deathtrap by the Legion and corrupt Nipton Mayor Joseph B. Steyn. Oliver runs into Radscorpions and if you save the Captives they run into Ghouls. So, its safe to say that this crew has been disbanded.

Other NCRCF Gangers

The unnamed Gangers found at Powder Ganger Camp North, East and West.

The Gangers around NCRCF (such as on I-15, I don't think the ones currently around the sacked caravan are Joe Cobb's Gang due to their lack of participation in the Goodsprings Raid).

The Primm Powder Ganger Ambushers.

Now for the Chavez Splinter Faction which could also be called 'Chavez' Crew' or the 'Camp North Splinter Faction'.

At Powder Ganger Camp North

Leader: Chavez

3 other members

Chavez refuses to respect Eddie's authority, so Eddie orders him dead. On the the matter of the other members of this splinter faction Eddie says "Chavez is the ringleader. Without him, his crew will fall apart, and I don't give a shit about those guys."

Now we go onto the Unknown Affiliation Powder Gangers who have no direct hints as to which faction they're a part of.

First we have Hawkins, named in-game simply as Powder Ganger he is found dead by Quarry Junction, implied to have killed a Deathclaw before he was killed by them. He was presumably killed a fair bit after the Gangers stormed and claimed Quarry Junctions Dynamite, which means he was either a loner, a member of the NCRCF Faction who went too far north or a member of Vault 19 who went back that direction.

Now we have the Hunter's Farm Powder Gangers

Located in proximity to Whittaker Farmstead and Vault 19, they nevertheless have no content cut or in-game that directly ties them to the Vault 19 Powder Gang and they use Powder Ganger Rep, meaning its possible they're a far-northern NCRCF Crew.