Ive a bit of loading too, under my belt.
Stretching can be controlled, its not voodoo or even rocket science. YOu learn that going through so many ARs and rounds a year, at one point wiht another family we were involved in a number of ARs and making sure that they all ran right and all loaded ammo was around 100K rounds a year...
In a small case, the ONLY way I'll increase powder is .1 at a time.
in 223 the ONLY way I'll increase is .2 at a time.
YMMV, I'm comfortable with whats worked for us for years and won for years and with zero of the so called blow ups or damaged guns.
heck I've even had some ammo piezo pressure tested due to concerns, to find it was just fine for what it was....
I would not be scare of a 5.7 either. I don't have a use for one, but would not bother me.
You have to understand a LOT of things in loading though, length of bullet, length of bearing surface, rifling you are using, any coatings, case capacity, chamber, ogive, lead angle and so on...
Folks that don't pay attention and substitute components on the fly can be asking for trouble if they are not backing off each time they change anything, including a primer etc....
