There has been some discussion here regarding the use of this
propellant. Oftentimes the comments remind us to use magnum primers with this powder.

Is that a “must do” perspective or is the use of standard primers something that has been proven acceptable? 

Thanks for your help!

Tom

The late John Louis filled my bucket with his experiments and experience with this powder. I've accumulated lots of cans of powder over the past fifty years but this is one I've never burned or been able to find. My stash has got this powder covered on all sides of the charts but John took its characteristics and performance a step further and found the secret hand shake. 

Like Olin/WW ball powders MP 300 has a burn retardant coating which generally needs hotter magnum primers to achieve full burn. John spent a lot of time testing primers with this powder. Other true magnum pistol powders like 2400, Blue Dot and AA-#9 burn okay without magnum primers but MP-300 needs hotter primers. John had it figured out and I'm sure those who shot with him in Central CA have the recipes 

Just Spit Balling
Rick

For a bit of reference on what john did, here's one of his targets he shot with the rifle i now have, downloaded it of here a while ago