reg primmers vs. mag primmers help

[T3man]

just a question to anyone who reloads, i've read some stuff that says dont use mag primmers unless the load data specifies that you should but on the other hand i've also heard of guys using the load i use with mag primmers (load data says use reg.) is there any gain or danger from using mag primmers?

7mm mag
60gr. h4831
160gr nosler accubond
rem case

[Dick284]

If you use prudent reloading procedures when developing loads, it poses no danger.

Prudent reloading procedures are:

- Always use multiple data sources
-Never start at a published maximum load.
-Work up loads from at least 5% off of max in 1/2grian steps.
-Never use data from a unspecified source. ie. some internet data
-Use a chrongraph, relying on primer marks, or flattening is not reliable, neither is sticky bolt lift.
-If any component is changed back off and re work your loads.
-If any lot number on components changes, back off and re work your loads.

In some cases Magnum primers can result in slower velocities and lower pressures, while in other instances the opposite happens.

My rule of thumb is, that if you are going to light up 50gr. of 4350 or slower powder in below freezing temperatures, a magnum primer is worth consideration.
All ball powders should use magnum primers.

Good luck

[sbtennex]

Take Dick284's advice.
All the loads I make up for my 7mm RMag call for a mag primer so that's what they get. Pressure changes (hence velocity changes) cannot be predicted by a simple switch to a magnum primer, so almost as a rule if the switch is made powder should be reduced by a minimum of 5% and fired cases inspected very carefully for any change in appearance of the fired primer. If they're now flattening at all and they weren't before (assuming same rifle and brand of primer) you're too hot. There's also no way to accurately estimate pressures by logging velocity changes - far too many variables. Sticking to the book is always the best way to make sure you won't have any trouble.

[jasonburrows]

Use the primers suggested mag primers create higher pressures I once accidentally loaded large rifle mag primer into a 44 mag round wich should have been large pistol mag (had one primer left in primer tube from last reloading session), split the 44 mag case in half and jammed it up in the blackhawk cylinder.

[bobinthesky]

Magnum primers are definately hotter than regular primers so if you're going to switch, make sure you reduce the load and work you're way back up.