Magnum primer usage

the mag primer just burns 'hotter' to give more consistant and complete burn. Although, you don't want to use mag primers in high pressure 'non-magnum' cartridges like 40S&W.

I have used the Win small pistol primer in some .357 loads with H110, and the performance wasn't the same as the same load with CCI Mag primers. THere was more unburned powder, and the rounds were a bit inconsistant, especially on cycling the slide of my Desert Eagle.

You can use mag primers in 9mm and .40s&w.. just lower your powder charge by 2gr.

In 9mm mags might be overkill... but I think that a mag primer may be used with a heavy powder like blue dot or 800x enabling a reloader to get similar performance without the need of powder compression. (my next range trip will be to test this hypothesis in .40)

FITH ........ ''2 grains''???

I mean .. my load of N-340 in 9mm is 5.5 grains ... I'd not expect to load down to 3.5!! with mag primers (if I were to use em!)

Do you not mean ....... 0.2 grain?

Sure ..... mag primers have (should have) a hotter burn but .....



I reckon mag primers come into their own only really with big loads of slow powder .... 2400, H-110 etc ..... in hot mag loadings.

*cough Cough*

Down 2gr and work up!

That's what I'm doing now with some hot .40 loads. Each 5 rd test has a companion with matching powder charge yet loaded with standard smalls so I can accurately document the change.

I believe it may pay off with 800x.

FWIW 20% may be a better way to decrease the charge... the powders I plan on using with the mag primers are in the 10-12gr range...

Magnum primers in small cases like 9mm and .40 S&W make HUGE pressure differances. In my early days of reloading I ran out of standard primers and made same LIGHT 165 gr .40 load with Universal but with magnums. HUGE case bulge out of my Glock 24P. Easily a millimeter. Cases wouldn't roll they were so bulged.

Took me a while to figure out what had changed. Didn't have a chronograph at the time so couldn't tell you any velocity differance but it probably would have been minimal.

What happens is the hotter and larger ignition source ignites ALL of the powder at once instead of it building pressure normally and giving the bullet time to unseat and move down the barrel creating more combustion space. Going with a magnum primer is much like switching to a much faster powder.

I have no doubt that if I had been loading full power loads and not very light target loads I would be bitching about how my POS Glock KaBoomed on me.

I load quite a bit of .357 and .44 Magnum full power ammo. I quit using magnum primers in handguns many years ago. I use only Remington standard pistol primers in all of my hanfgun loads and I 've had very good results.

Thanks, kamicosmos.

Got some H110 I want to work through for my Win94 357mag lever gun, but ran out of magnum primers. Guess I'll go get some more rather than try it with standard primers.

Last friday I loaded and tested some reduced 800x .40 s&w 135gr loadings with and without mag primers.

FOLLOWING IS LOAD DATA THAT HAS NOT BE PRESSURE TESTED FOR SAFETY! THESE LOADS DID NOT BLOW UP MY GUN BUT MIGHT YOURS. USE AT YOUR OWN RISK!

From a G22 standard barrel (4.5"), 65F, winchester brass.

With 9.0gr of 800x, 135gr nosler, an OAL of 1.130", and a winchester small magnum pistol primer I only got a 22fps gain over the control load.

At 9.5gr with the same conditions velocity gain was 105fps....

Note: From my previous trials, 800x proves to be fairly inconsistent with a high standard deviation. I think for the bulkier powders one should expect a gain of 50-100fps as you near max pressure.

For the complete workup go
here and look near the bottom of the page.
-FITH