CERTAIN POWDERS are dangerous with reduced loads
Certain powders are NEVER to be used for reduced loads. They are the slower powders and if they don't generate sufficient pressure are apt to have pressure spikes. These are completely unpredicatble and have given ballisticians fits for decades because they cannot be reliably reproduce in the laboratory. Someday, perhaps. They are still working on it.
H110 is probably the most well-known of the powders not to reduce. H110 is a really great powder, but NOT for reduced loads (according to its maker).
The advantage of the slower powders is that they (when properly pressurized) burn for a long time, impelling the bullet with steady pressure and less felt recoil. Faster powders don't have the burn time to reach high velocities unless you use a lot of them, which produces higher pressure over a shorter time than a slower powder, higher peak pressure to achieve the same velocity and more felt recoil.
The maker of H110 advises to not reduce the maximum load any more than 3%. Check their web site.
If you want moderate velocities, use faster powders. This is why we tailor loads and pick powders that 1) give enough pressure to expand the brass to seal against the chamber walls, 2) give enough pressure that the powder burns as it is supposed to, 3) produces enough pressure for a long enough time to ensure the bullet does leave the barrel and 4) produces pressure below that which will damage the gun or the shooter.
For every desired velocity, there is a powder that balances peak pressure and burn time for optimal efficiency. The handloader's task is to find it. It keeps those who are of a personality for it interested. Kind of like searching for the Holy Grail or working out a puzzle. A really LOUD puzzle.
Good Luck. Be safe always, all ways.
Last edited by Lost Sheep; June 16, 2011 at 10:08 PM.