I didn't end up actually building any alloy rifles. I just ran up and point blanked **** with plasma rifles, called it a day.
I built one just to see how they work. They DO hit harder than Plasma Rifles up close. I thought it was a good trade off. Slap it on an Assault guy with Run&Gun and then double tap at point blank. Drops baddies pretty quick.
with 40k its best to get the rules straight then apply imagination and rationalize; you will only get annoyed doing it the other way round
~Bullymike