magnum primer equals how much velocity increase?

R

ReloadKy

New member
I have never used a magnum primer in any of my rifles. I have been using Winchester large rifle primers in everything I reload including my 7MM Rem Mag. My question is, how much velocity increase have any of you experienced when switching from a large rifle primer to a magnum large rifle primer?

The reason I asked is that I have started to shoot longer distances and I am trying to some cost analysis between buying a new powder to try for more fps or trying the magnum primers. Thanks for all info.
 
You don't use a magnum primer to get more FPS. You use a magnum primer ONLY because the particular powder you are using requires it.
 
As I recall,the WLR,while not designated a "Magnum" primer, MIGHT be specified for a book load in a cartridge like the 7mm Rem.
The thing to do is use the components specified by your load manual.

The concept of hot rodding by going to a hotter primer might be OK racing out a Techumseh motor for your highspeed riding lawn mower,but you are talking about tinkering with over 60,000 psi hot gas a few inches from your eyeball.


Something to think about,if the spec'd primer already gives you a MAXIMUM PRESSURE load,and IF you got more velocity from a magnum primer,where did the velocity come from? More pressure? Huh?

Yes,sometimes you CAN bump up PRESSURE with a magnum primer.

Bumping up pressure can increase velocity. I wildcat some.I develop my own data,some. I look at many things. One indication I have "hit the max load wall" and pressure is spiking is when my chronograph tells me I don't get as much velocity for the same charge increase. You reach a point where pressure is spiking faster than velocity.


When your manual calls for a magnum primer,use one. Use THE one they ask for. Some powder is harder to light up.Its harder in larger cases.

Sometimes a hotter primer gives more consistent ignition,for more uniform velocity,and better accuracy.


If you had a two stroke chain saw or dirt bike,would you put in a hotter than recommended spark plug for more horsepower? That's one way to put a hole in a piston.
 
ReloadKY,

You're barking up the wrong tree, I'm afraid.

In large primer cartridges, the difference is often close to zero. Sometimes you actually get lower velocity from a magnum primer because of the way it was formulated taking too long to add its extra gas. But usually, you get a little bit more. For example, in this test of 16 different primers in .308 Win, the difference from lowest to highest velocity was 25 fps out of about 2800 fps. Here's the irony: the lowest velocity was from a Remington 9½M, a magnum primer, while the fastest was from the same company, the Remington 9½ LR, their standard large rifle primer.

At the other extreme, I remember Handloader had a test of a 223 load with a Reloader 10X and a 55-grain V-max that went from 3150 fps to 3300 fps with the hottest primer. Probably about a 10% pressure increase.

Anyway, the bottom line is that, especially for the larger cartridges, changing to magnum primers to try to get more velocity is pretty much just a way to spend more money for much the same performance. You'll be way better off increasing powder quantity.
 
Magnum primers tend to burn hotter and are often recommended for ball powder and cartridges that have to ignite larger volumes of powder. Your 7mm Magnum is right on the borderline of needing magnum primers. But the Winchester primers you're using have a reputation of burning hotter than many "magnum" primers. I wouldn't change if you're happy with the results you're currently getting.
 
Magnum primer use is more about getting more consistent burns on powder charges or slower burning powders then actually increasing velocity. As stated above, certain ball powders ( BLC-2, XBR, CFE223 etc) can see gains in velocity in calibers like 223/556 and 308 but more often then not it results in lower SD/ES's as the burn is more consistent. In powders like VARGET and RL 15 the difference is nearly non-existent due to the stick nature and the minute gaps in the charge providing the perfect environment for standard primers to do their thing.
 
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