As chris suggested start with a revolver caliber (preferably) as you can adjust powder to lead hardness or softness .
A lee hardness tester is accurate as long as it`s used correctly (the scope is a booger to hold so I came up with this , Don`t laff it works !!
I`m entering the world of 6mm&243 casting & have found the faster twist smallbore calibers are a daunting task , they need hard/tuff bullets to be able to go fast !!
1300-1500 fps is no problem but I`m reaching for 2K
Now back to alloy & what to expect , if ya got some wheel weights use em 50/50 with soft & 2% tin (for a total of 4%tin) for a soft "tuff" bullet for revolver rounds 10-11 bhn if sized to the throats & the throats are equal to bore ya should have no problem to 11-1200fps.
Weight of a given mould does`nt cocern me it`s the size it drops , alot easier to size down than to make em swell !!!
Tin does`nt help after 2% to harden so don`t waste it or an alloy hi in tin .
Antimony in linotype what makes hard shiney bullets !!! good for rifles ,but the harder they are the more likely to shatter upon contact with bone or even soft tissue when hunting !
It`s an age old balancing act in the shooting world for shore!!!
Just a few thoughts leaking thru the key board
For casting overload go to :
http://castboolits.gunloads.com/
& read a bit ,heck join up & ask away !!! good folks here & there , some here are members there also !!
Just remember the most common mistake of noobs is trying to pour bullets(they frown upon boolits over here) with too cold a mold & alloy !!!
Get em both clean & hot & succes will come qwiker !!!
GP