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Im not telling you to use them...but I do and only on loads I have specifically worked up.  The WILL raise pressure and may flash your powder (a real bad thing).  I would only use in large cases and will ball powder which is a bit harder to ignite as well.  I caution against it in 223/556

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What is "flash your powder?"  Sounds bad.

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do you have to reduce your loads when you use the mag primers? usually , YES
are the loads listed in the reloading books worked up for standard primer use? it should tell you which they use on the first page of that particular rounds data
whats a good load using h335, ss109's and magnum primers?I don't know

Magnum Primers
Most components primer manufacturers, including CCI® to reloaders offer Magnum primers. Under certain conditions, reloaders need a more powerful primer than standard primers. It's much like buying a new car and deciding whether to get the standard four-cylinder engine or a more powerful V-6.

When we develop load data, we consider these conditions as indicating use of Magnum primers:

With ball or spherical powders (some exceptions exist)
With large-volume cartridge cases
If the cartridge is likely to be fired in cold conditions (under 20° F)

Magnum primers are engineered to produce a hotter flame of longer duration to meet the needs of the above conditions. However, these characteristics often require a charge weight reduction to keep pressure under control. For this reason, use Magnum primers only where recommended in published loading data.

Our research indicates that some propellant/cartridge combinations do not require Magnum primers at the maximum load level, but can at the start load level for reliable ignition. When we find this, we use Magnum primers for all loads with that propellant.