Again, that's different than how I interpreted it.
Every weapon has 2 values - shots per load, and max (capacity) you can carry for that weapon. The Mantis was 1/9, meaning you needed to reload after every single shot, and you could never carry more than 9 shots total for it (capacity). Predator is 12/60, Locust is 20/240.
Start a mission w/ those weapons and a full load of clips, take your 9 shots with the Mantis, and you'll still have 60 shots' worth of clips for the Predator and 240 for the Locust. Take a dozen shots with the Predator to complete the battle, and the first clip you pick up may refill your Predator's capacity or that of your Mantis. You'll need to pick up more than one clip to completely refill your Mantis, however.
At least, that's how I remember it working - it's been quite a long time since I played ME2.
I wasn't saying that's how I interpreted it. I'm saying that's how it should have worked if we were going to get nitpicky about "not following lore".
The way it worked in Mass Effect 2 was that every weapon consumed ammo separately. Firing a shot with your Mantis only consumed a "Mantis ammo", however picking up a Thermal Clip gave you a pre determined amount of your spare ammo back for every gun you had. This wouldn't account for your current "clip" being partially empty like in Mass Effect 3, so if you wanted to get back to 72 total shots with your Predator you had to make sure to reload the gun first.
If one wanted to make it 100% strict lore following the way it would need to work would be:
1. Since spare ammo is just thermal clips all guns need to have equalized spare ammo. So it would change to say 1/9 Mantis shots, 12/108 Predator shots, and 20/180 Locust shots. Basically you can carry 9 spare thermal clips(or whatever the number they decide on would be).
2. Reloading the Mantis now reduces your ammo count by 1 Mantis shot, 12 Predator shots, and 20 Locust shots. This is because you consumed 1 out of your 9 spare Thermal Clips, so all guns lose the ammo that they could have gained from that.
3. Reloading a partially expended Thermal Clip now makes you lose the entire rest of the clip. If you fire 6 Predator shots and reload, you lose the remaining 6 rounds(as well as the Mantis and Locust rounds).
What I'm noting is that I don't think people would have been happier with that system if the complaint was they felt ammo was too limited, unless they drastically increased the total capacity of Thermal Clips you could carry which is just increasing the ammo count which has nothing to do with making them a universal pool.
That's great - but since a lot of the battles throw more enemies at you than you have SR shots available, you will need to use powers, swap weapons, rely on squadmates, melee, and/or pick up clips to get through some of them. But I've pretty much said that all along.
The goal is to use only sniper rifles for the entire game and basically never fire another weapon. I'm still allowed to use powers and picking up ammo is fair game(although I will avoid using nothing but powers to beat entire fights). The only exception will be the first mission where I'm limited to just a pistol, but as far as I recall there isn't any other cases of that happening in Mass Effect 2. I also basically never used melee to begin with in ME2 anyway.
This is an experiment as to if a playstyle is viable(in this case, playing with strictly a sniper rifle as my firearm), not how badly I can gimp myself while still being able to beat the game. Not using powers makes as much sense to me as saying "I want to beat Mass Effect 1 without spending a single skill point while wielding an unmodded Avenger I as my only weapon".
Most likely I would play as an Infiltrator and rely primarily on Tactical Cloak and Disruptor Rounds to increase my sniper rifle damage. The alternative is Soldier, but I don't think I'll need the time dilation of Adrenaline Rush to increase headshot reliability.