RL-15.5 ????? what does the .5 tell us about this stuff///

"Normally" a higher number is Slower.
So, being point five, 1/2 step. Just faster than Reloader-17.

I think RL15.5 is a temperature stable version of RL15
Probably the burn rate differs a fraction as well.
But for confirmation go into thd Alliance website and read their info.

It would be wonderful if the .5 meant another 1/2 pound in the bottle at the same cost

It's not too hard to use Google.
https://www.alliantpowder.com/...r/reloderts15-5.aspx

quote:

It's not too hard to use Google

For some it is.

Great minds just come with something new when they cannot keep up with old standards. They are just following Hornady's example! Ha Ha