You do not say how you tested the 1300 samples or how you will test the next 850 samples.
But this seems like a very inefficient and costly way to test this quantity to find a reliability (unless you testing something like rivet strength).
Have you looked into conducting a statistical sensitivity test (e.g. Neyer)?
Incidentally with 2 failures in 2150 tests yeilds an approx reliability* of .97175 @ 90 confidence. (with no failures R = .9989)
* I use the approx formula given by Ireson & Coombs.