Hey, I found Fluid Film is a great penetrating oil also.
I do believe the rear sight is not dove tailed on the 15. The front sight is. You should see a visible line on the barrel and blade that shows center. There are sight adjusting tools that will work best. I've used an AK/SKS on these types as it will slide over the barrel.
As stated, a brass punch, hammer and wood block would work. I bet if you tried some different ammo your poi would change.
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