I've been told that you need to worry more when shooting heavier vs shooting light.....so if a 1:10 works for 50gr, it should shoot 36gr ok/well, but if you wanted to shoot 75gr, you could run into some problems.

if 1:10 is ideal for 50gr, then over 50gr, you would want a tighter twist....like a 1:8, for lighter bullets, a 1:12 or 1:14 may be ideal.

though if a 1:14 would be ideal for 36gr, and then you used 50gr in it, accuracy may be thrown out, so I think manufacturers tend to use tighter twists, to cover the spectrum better. ie a 1:8 would work better for everything, whereas a 1:14 would only work for the lighter bullets.

Sure other guys will have a more precise answer for you.

If you do decide to use that rifle with the 1:9 and barnes recommends a 1:10 for 50gr, but you want to shoot 36gr, you may consider using a heavier load, or another rifle/barrel with a twist more ideal for lighter loads.