Combo (not combat) detonations are defined by the primer. So you can have a fire, cryo, tech or biotic combo. All ammo and some skills can prime. Some skills prime right away, others must have points allocated in the skill tree for a prime capability, some skills cannot prime (or detonate). There is no combat primer, hence no combat combo detonation. But … concussive shot is combo detonator.
For me, the best combo character is the Asari Adept … she rocks the joint. Spec her out with Annihilation Field (primer) and Throw (detonator), leave a single point in Lance (detonator)… then go to town with biotic combos. You'll complete the combo challenge in no time. She's an up close and personal fighter … but once you get the hang of her, you can rock the joint all the way through Gold.
Barricade can do damage on it's own and prime if you select electric defense on level 6 skill tree. Otherwise, it does no damage. Instead, it boosts offensive and defensive capabilities.
The damage it does is small. Normally, I either put no additional points in Barricade or two at the most (a total of three).
For the challenge, I respect my character (such as the Salarian Architect, Angara Avenger or the human Sentinel) to fully evolve the skill, then I run solo bronze missions, using the barricade as a weapon. It takes a while to score enough points. At higher levels or playing with others, it will take even longer … since most enemies get shot or blown up long before the barricade does much damage. But eventually, you'll score enough damage to complete the challenge. Then go back to running the barricade with either 1 or 3 points.
It's useful at a single point … I use it a lot when running one of the characters that have that skill … mostly for enable objectives if I'm doing it or protecting a teammate if they are doing the objective. Also, it's handy for hacks, uploads or extraction, when all four folks are competing for limited cover.
Yeah … there are no combat primers, so no combat detonations combos. Concussive shot is a combat skill combo detonator (edit correction: in Combat Mastery, combos caused by combat detonator's is an objective … but the resulting combo will register as a tech/fire/cryo/biotic combo).
Check this combo page out on the Wiki … it lists all the primers and detonators.
Barricade is a combat skill … but the primer option in the skill tree is a tech (electric) primer, not combat. Purging the combat skill "Fortify" … if evolved in the skill tree, will prime a critter for a tech combo. Avenger strike will also prime targets for a tech combo if evolved in the skill tree.
Most likely, the challenge has the wrong word (combat instead of combo) and was never fixed. Combat Mastery has a combat detonation objective … different from the daily combat challenges.
The nature of the combo is determined by the nature of the primer, not the detonator.
The Human Commando, with two biotic skills (and a non-priming/non-detonating combat skill) can get tech, fire or cryo combos if she's equipped with disruptor, inferno or cryo ammo respectively.
Or if she hits a critter with her warp that was already primed by a teammate … she can get all of the above, plus a biotic combo if the primer was biotic.
She can prime a critter with a biotic singularity and detonate with warp … or she can prime with her warp and a teammate can detonate … but she can't both prime and detonate the same critter with two hits from her own warp.
In all cases, critters she primes with either singularity or warp, if detonated by her or someone else, will yield a biotic combo detonation, regardless of the character of the detonator.
Hope that helps. It's not intuitive, that's for sure. Good hunting!
Speaking of not helping … totally misunderstood what you were asking … I went on about combat challenges, you were asking about Combat Mastery. Sorry. See below for some better info.
Indeed there is a combat challenge … which is different from combat mastery. And you'll find that with the dailies, there are combat challenges, tech challenges and biotic challenges … or daily challenges in regards to levels (bronze, silver or gold), or factions (Kett, Remnant and Outlaw) and every daily challenge has a specified map. These are in addition to the Apex mission modifiers.
Combat challenge points will go up for things like grenades (sticky and frag), flak cannon, trip mines and concussive shot. My favorite combat character is the Batarian Scrapper. You might not have him yet, once you do, the combat challenges become pretty easy (today's daily was a combat challenge on Derelict). I use him, because he has flak cannon and concussive shot. I don't use flash freeze (his third skill, which is a tech skill) on the challenge and I don't shoot stuff unless absolutely necessary. I spec him with added charges.
Avenger Strike is also a combat skill, but it counts as melee. Guns and melee don't count toward combat challenges. Fortify is a combat skill, but it reduces damage and if the skill tree branch is selected, primes targets for a tech combo … so it doesn't do anything for your combat challenge. Avenger Strike does count for combat mastery … i.e. kill a bunch of stuff using avenger strike.
Whatever characters you have, pick one with grenades, flak cannon or concussive shot … those are the ones that will help you complete the daily challenge.
I misunderstood what you were asking for earlier … the Combat Mastery (bronze, silver and gold) is different than the combat challenges. Barricade is part of that, as is Avenger Strike. The combat detonations are not specific types of combos … it's the one time the detonator type matters. So I've been giving you bad info … let me back up and try again because I've made a hash of this.
For Combat Mastery … using combat detonators to do combos … you'll still get the indication that it is a fire/cryo/tech/biotic combo … because that's all there are as far as types of combos.
There are only two combat skills that can detonate. Grenades and flak cannon can't detonate primed targets.
Concussive shot starts out as a detonator, even at level 1.
Trip minecan be a detonator, if you spec it that way, but you'll have to go to level 6 and select detonator (the other option is as a tech primer).
So to score combat detonations, you'll either have to play a character with concussive shot (M/F Human Soldier or Batarian Scrapper) or trip mines (Angara Insurgent) (with detonator selected in evolution 6).
Sorry about that, wasted a lot of your time answering a question you didn't ask, instead of the one you did.
I found that the fastest way to get Combat Detonations was to use Concussive shot spec'd for Grenade charges. Then unload them onto targets inside singularity or annihilation fields. It's dependant on team composition, but the good thing about these primers is that they're constantly priming. There may only be one boom, but the killfeed will show combos on every concussive shot.
You see a Hydra or Fiend in a singularity and unload all your concussive shots, you'll get quite a good amount of combos.
For solo play, Batarian Scrapper is best. Snap Freeze a group of unprotected targets and then detonate with concussive. If you're bronze/silver soloing against Kett or Outlaw you should be able to knock this combat combo challenge out fairly quickly