Let me add another side to this discussion. I won't get into exactly how many 12 grams I have used, but suffice it to say that I have been shooting only first strikes for the past three years. lnitially, I shot those rounds through a Tiberius T8, T9, T9.1, and, now, through two different SR1s. Up till about a year ago, I ran the Tiberius guns exclusively with 12 grams. I don't care about efficiency. I only care about accuracy and velocity swings impact accuracy.
Initially, I went away from HPA with an Electro because I hated, really hated, using a remote line and filling HPA bottles. Accuracy was the reason I jumped to first strike years ago, but doing away with HPA tanks, air lines, and hoppers was a huge bonus. I sold all that stuff when I bought into the first strike gear.
About a year ago I started conversing with some other serious shooters who were getting +/- 2-3 FPS on their T9.1s using HPA. No matter who hard I tried, I could not duplicate that (or even come close using 12 grams). My swings were in the +/- 5-10 FPS range. Reluctantly, I purchased the 13/3000 CI HPA tank and tested that. My consistency immediately improved to +/- 3-5 FPS.
When I first got an SR1 Protype, I tested the gun using both HPA and 12 grams. While the SR1 was slightly better than the T9.1 with either propellant, the differences between 12 grams and HPA were still apparent to me. I probably shoot over a hundred rounds over the chrono just testing the gun's velocity with 12 grams and HPA using different velocities as starting points.
A couple of things were apparent to me during the testing. When I first put in a 12 gram, the velocity usually spiked a bit. Not much, maybe 6-8 FPS higher than usual. Also, before the gun ran completely out of air, the velocity began to drop just a bit. Not a lot, and probably not noticeable to the eye of the shooter, but the chrono saw it.
When I bought my own SR1 I ran the same tests on it hoping for a different result. I reached the same outcome. With HPA in my SR1, I am seeing +/- 2 -3 fps difference. With 12 grams, I see a +/- 5-8 FPS variance.
Your own mileage may vary and, for some players, those kinds of small swings may, in the end, not mean enough to make much difference to them. In fact, for most players that kind of variance isn't worth buying and lugging around a small HPA tank and remote line. Let's face it, the SR1, no matter how you shoot it, is a very consistent gun. Unfortunately, for me, a +/- 5-8 FPS velocity variance means I will be carrying that Ninja tank and using a remote line.
Just another line of thought.