I got the 3 kills in 1 life using a birthright or Truthteller. The bit I struggled with was the double kills. I ended up using Tether and a mix of the Colony or a precision GL’s. Mayhem is best for it because heavy ammo drops like candy.

Found a dirty combo for titans. Ashen wake gauntlets make fusions explode on impact on any surface. (Bottom tree solar)So that plus a grenade launcher is disgusting

Oh, also, search Google for "mountaintop quest tips' and there are several reddit posts that have tips as well. I found a lot of tips because this is the first quest I felt like I REALLY needed them. I did searches such as "mountaintop quest sucks", mountaintop quest is outrageous", etc... lol. It can be really frustrating at times so you HAVE to have patience and don't let it get you too tilted. Again, I played nothing but crucible for 3 weeks, using GL in every slot most of the time. 3 hours a night for 3 weeks and it took me a total of 21 hours of gametime or so. It doesn't seem like a ton but trust me, it sure feels like it while you are working on the quest. It has to be the longest and most challenging thing I've ever done in Destiny, I'm pretty sure.

Hunter tether with fighting lion (especially with catalyst) and/or militias birthright...warlock empowering rift with fighting lion and/or militias birthright. Or...you can JUST run colony in your heavy, hover around heavy at all times and pick it up, then unload your 5 shots as soon as you hit a group of people. If you are already decent with GL, a lot of people preferred using play of the game or something similar which allows the use of fighting lion as well. At times, I was making progress as fast or faster, just by using regular weapons to hold my position at heavy and getting colony kills as i did by running around with FL and Militias Birthright. I also ran militia and orewings maul(which allowed me to equip colony) at times but you only get one shot for each per life so you have to make it count. Mayhem is really good for using the hunter and tether strategy but it takes a bit to get used to doing it as there are constant supers all around you. You have to play really conservatively, shoot your tether at ceilings and bait people in as much as possible (because some supers can run through it without being tagged and kill you before it activates.) You can also use mayhen with the colony because heavy spawns constantly around the map but you want tether still because its much harder to kill supers with colony than guardians not using a super, and in mayhem, supers are pretty constant. In quickplay, you can use the empiwering rift and lunafaction boots to spam Fighting Lion at enemies AND it one hit kills them IF its the EMPOWERING rift, NOT the healing rift. I ran triple launcher for a long time and got really frustrated at my slow progress at times(which btw, all those tips I gave are mainly for the double kills). The calculated trajectory medals and overall kills will happen as you focus on doubles, so go for those until they are complete. I completed the doubles and was at 83% Calc medals, so I had to finish it and it was a bit easier because all you have to do is focus on one enemy at a time and stay alive. 3 in one life and bam, you have a percentage imore as on calculated trajectories. Do it all in quick play or mayhem(lockdown works well too because there are zones people HAVE to take and group up on). I advise not doing it in comp because there are less enemies for multi-kills, it's more difficult competition, and overall tougher to get the required kills and medals (even though you get more progress for doing it there.) Whatever you do, BE PATIENT, it's the toughest quest I've done in the Destiny series BY FAR and took me 3 weeks of nothing but GL and crucible matches. I got very frustrated several times because GL can be inconsistent and I didn't get progress for certain situations I thought I should have. In the end, the gun is tons of fun (even though it's not a top tier option), and it feels great to accomplish something that you know not many people have because it's difficult and time-consuming. I also don't know how easily you will get progress during the revelry with unlimited grenades going on but good luck! I think that's all the advice I have for how I did it but if I think of something I missed, I'll update your post. Oh, the reason I keep saying to us tether is because having 2 or more enemies tethered, and killing one, not only shares the damage but counts as double kills with a gl. If you have 3 tethered and get a kill, it's an automatic double kill AND calculated trajectory medal. Not nearly as easy as it sounds to simply keep tehtering groups and killing them with fighting lion though lol. Mayhem will drive you crazy because you have to go FAST. I can't tell your how many times I tethered groups for them to be killed by a blade barrage or some other super before I could fire my shot. I was getting super tilted at the randoms taking advantage of my tethers. I definitely yelled "does it look like I'm tethering these guys for you to kill?" many, many times lol