Adding Mag primer to your load

[MGYSGT]

I have always read that adding a mag primer to your load, equals adding 1 gr. of powder. Is there any real evidence to support this statement or is it just a SWAG?

Tom

 

[necchi]

It's just a rule of thumb guideline that's used help people understand that there will be a change.
The actual powder, case and application are the variables that determine to what degree the change is.

If a guy thinks he'll save a .1grn of powder for each load and make up the difference by using a mag vrs standard primers and keep all other things equal,,
Well, :-\

 

[357Mag]

MG -

Howdy !

Can say that w/ my 6mm wildcat of case capacity in 6 X 47 - 6XC capacity range, change from use of FED LR Match to Fed LR Magnum Match boosted vel by 80fps, while groups opened slightly.

Barrel: 28" SS Broughton 5"C" 6mm

Loads: Sierra 95 MK 40.5gr AA3100 FED LR Match = 3,420fps
Sierra 95 MK 40.5gr AA3100 FED LR Magnum Match = 3,500fps

Found this vel difference out, while wringing out various primers; tryng to find the best grouping load.

Ended up going w/ use of FED LR Match in the load, for se on both paper ; and groundhogs.

* You results may vary


With regards,
357Mag

 

[markr]

It would depend which standard primer you are using and which mag primer you are going to. There is not a formula for an answer that I know of except that you reduce the load 10% when you change any component and work up to max (if thats where you're going). This is a basic reloading rule found in all good reloading manuals!

 

[MGYSGT]

Thanks for the info. Was just woundering if any one had done testing to prove or disprove the statement. Looks like 357mag did a little testing and found velocity changes that seem to indicate more pressure.

Tom