The Firearms Forum banner

Magnum Primers

2K views 18 replies 11 participants last post by  gdmoody 
#1 ·
Ay what point, if any, do you go from large rifle primers to the magnum primer? Are they really needed?
 
#3 ·
Magnum primers are recommended for powders based on ignition requirements. Some powders ignite more efficiently with magnum primers, while some powders do not need the effects of magnum ignition. Remember, by using a magnum primer in place of a standard primer, will affect the internal ballistics of your load, you could see an increase in chamber pressure, and/or a (+ -) difference in velocity.

In most cases, your reloading manual will recommend when to use a magnum primer for powders that perform better when used.
 
#4 ·
Like howlnmad said, in cold weather a magnum primer will help ignite your powder a little better. In particular spherical, double-base powders are harder to ignite as the temp drops compared to single-based (usually an extruded/stick form) powders.
A magnum primer has a bit more priming compound and will give you a larger flame for ignition.

I use magnum primers for almost all of my spherical powder loads, but especially my winter ammo for the yote rifles.

And also keep in mind that there are magnum primers available for both sizes small and large. Small rifle, Small rifle mag, large rifle, large rifle mag, etc...


Generally, and especially for a beginner, stick with what your data source recommends.
 
#7 ·
I have seen large loads of H110 clumped in a chamber/barrel from standard primer not igniting the powder. Powder was good, other loads worked well with magnum primers, just not enough "ummmph" from a standard primer to ignite a heavy load of a slow burning powder. Some powders are harder to ignite so a magnum primer is needed (H110/W296, and WC820 I reload gets a magnum primer). I mostly go by reloading manual recommendations...
 
#8 ·
What puzzles me is why Winchester came out with large pistol primers that say they are good for both standard and magnum loads. I guess the explosive charge is somewhere between standard and magnum strength meaning it is not optimized for either one.
I just noticed that the other night while in Cabelas. What up with that?
 
#12 ·
What puzzles me is why Winchester came out with large pistol primers that say they are good for both standard and magnum loads. I guess the explosive charge is somewhere between standard and magnum strength meaning it is not optimized for either one.
I just noticed that the other night while in Cabelas. What up with that?
Those are WLP, which is a Standard Large Pistol primer.
They have had that statement on their boxes back at least 20-25 years when the boxes were still white with the red/orange and horse-n-rider logo across the top.
Not sure why they chose to label them that way except that they don't have a Large Pistol Magnum primer in their lineup.

They also don't have a small rifle magnum primer in their lineup, just the WSR.

For small pistol and both large rifle, they do have standard and magnum primers.
 
#13 ·
What firearm, powder, bullet are you using? Large charges of slow burning powder need a mag primer. Most everything else uses a standard primer
I'm considering the magnum primers for 7mm Rem Mag/.300 Win Mag and .300 Weatherby Mag. Powders for these include H1000/H414 and H380. Maybe IMR 4064, Retumbo and Magpro although I haven't loaded any of these yet.
 
#15 ·
For those big magnum cases (the belt has nothing to do with it...just the large case capacity), I would definitely use a Magnum primer if your load data calls for it even for the extruded/stick powders. There's a lot of powder to ignite in those cases.
Start out with the min loads and the mag primer and work up from there.
If you already have a load brewed up that uses a standard primer, be sure to back it off and work up again too. It might wind up being the same charge or it might not...too many variables to predict so it's always best to load safe. :)

H1000 and Retumbo are stick powders. But are slow burners and, as mentioned above, benefit from the hotter ignition of a magnum primers especially with large charges.
The rest you listed are spherical powders and they usually perform better with the hotter ignition too even in smaller charge weights.
 
#18 ·
Local gun shops were out of magnum primers. I loaded a half dozen rounds of .300 Weatherby Mag using standard large rifle primers and 80gn of Win 780 Supreme with a 165 gn Nosler bullet. The rounds fired fine. I have my order in for LR magnum primers since that's what the book calls for.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top