Hay Morgan, congrats on the new to you 1270.
I never noticed any better target separation when running in iron disc. Being I am only a coin and jewelry hunter when I ran iron disc it was set at max.
Now it was my understanding that the iron disc had some ability to see through iron, but I was never able to prove that.
As for that blast mode, I never really proved it was deeper but at the time I was told that the higher I could run the sensitivity the deeper it would detect. So I maxed it out and let her crackle and pop, then I was really surprised when I hit a good target and it stopped all the noise long enough to give me go clean target tone.
Shooter was my teacher so maybe he will pick up on your thread.
Now by far that little 3.75” coil was my favorite coil, but not just any of those will run on the 1270. If you go looking for one it needs to have the thicker coil cable. Note your 1265x box coils may have the skinny cables. You may have tried your 65 coil on the 70 but my guess is it will plug in and work but it will not detect any depth. Now I think you can put the 1270 coil on the 1265x and it will work just fine.
Good luck, and let us know how you are doing from time to time.
Ron in WV