What determines the need for Magnum Primers?

[Shootist43]

Like many of you I have more time on my hands because of the "Social Distancing" currently being the thing. I thought it might be a good time to load up some of my odd-ball calibers. I have enough of the stuff I normally hunt with to last longer than I will. But there are lots of other calibers in the safe that I've never reloaded for. All of them have the word "Magnum" in the caliber, i.e. 7mm Remington Mag., 300 Winchester Mag., 300 Weatherby Mag., 308 Norma Mag. and 338 Win. Mag. My question is this, do all of these calibers require the use of Magnum primers? I put them into my reloads for 375 H&H Mag., 404 Jeffery and 416 Rigby, but are they required for the smaller stuff as well? Is there a drop in velocity when standard primers are used? If so, is it significant?

 

[USMA84DAB]

.338 WinMag has CCI200 primers in AnyShot You Want - that is regular large rifle primer, not the CCI250 magnum, in spite of it's name.

.375 H&H has CCI250s listed

 

[Dewald]

The volume of the case and subsequent column of propellant that needs to ignite. It doesn’t have as much an influence on velocity as it has on consistency.

As a rule of thumb I use Magnum primers on anything with more than 65gr of extruded powder.

 

[crs]

Follow the above example and look at common reloading manuals such as Lyman. You can also find all that information by searching the Internet.

I use Federal mag match primers for any long powder charge that is compressed.
This includes heavy bullet loads for my .405 wcf and .45-90 ( powder capacity is 96 % of .458 Win Mag) .
Gives a clean 100% burn!

 

[Shootist43]

I had my suspicions about what the answer was most likely to be. A quick search of the net provided the following: https://www.grafs.com/uploads/technical-resource-pdf-file/12.pdf

 

[Wyatt Smith]

The Speer manual suggests using a magnum primer on most ball powders, like W760. Or at temperatures below 20F and for charges over 60 grains.

 

[samu]

The volume of the case and subsequent column of propellant that needs to ignite. It doesn’t have as much an influence on velocity as it has on consistency.

As a rule of thumb I use Magnum primers on anything with more than 65gr of extruded powder.

Recently someone claimed they get 100fps more out of 9.3x62 with magnum primer using 4g of N540. Not sure if they included higher pressure required for flattening the primer though.

 

[crs]

samu,
such increases are not uncommon when switching from standard to magnum primers. In one case (Pun intended ) with 400 grain Woodies in my .405, I gained 37 fps when switching from one magnum primer to Federal mag match primers. This resulted in an average velocity variation of zero ( 0) and a pressure peak somewhat above the factory average but still below 50,000 psi. The rifle liked that load and so did the cape buffalo.

 

[TNDave]

Simple rule of thumb I follow:
powder charge >60 grains = magnum primer.

nothing scientific about it, just keeps it simple.

 

[EricB]

I use magnum primers in all my rifle rounds, and adjust the powder accordingly.

 

[Newboomer]

If my rifle caliber says magnum I use magnum primers. Otherwise, it's LR.

 

[bruce moulds]

shooting in sub zero temperatures might require a bit more ignition.
bruce.

 

[DrBob]

Just for grins I have loaded my 470 NE with CCI 200, CCI 250, Fed 210, WIn WLR and Fed 215. With Varget (much slower powers without compression may not be as consistent)
CCI 200 + 3 grains powder= Fed 210
CCI 200 + 5 grains powder= Fed 215
Comparing same load of 85 gr Varget:
WLR - 2131
215 - 2211
250 - 2185

Winchester recommends loading the 300 Win Mag with standard WLR.
The present day CCI 250 is not the same as the modern day Fed 215... versus what was noted in the A-Square book.

I've used CCI250 in match loads for 308 and 30/06 with adjusted loads. Federal African loads seem to be all 216 primers. So... pick your poison... but staying with CCI 250 or Fed 215 for any larger African caliber is a good choice. Anything with a "Mauser" class case (7mm, 8mm, 9,3 etc) standard primers are fine.
`

 

[Opposite Pole]

shooting in sub zero temperatures might require a bit more ignition.
bruce.

The largest case I use standard primers on is 9.3x74R (Fed210M), I’ve shot it in -20C (-4F) with no issues. I know it’s not a giant case but it’s certainly not small either.

 

[fourfive8]

Just a footnote in the current age of component shortages. I found an interesting "nugget" of information about one brand/type of primer. The CCI #34, Large Rifle primer for semi auto rifles, is actually a CCI Large Rifle Magnum primer with a slightly tougher cup. The #34 was designed to help prevent slam fires in those rifles so prone- like a worn out Garand.

I've been using a chronograph to work up some magnum cartridge loads. Good, relaxing activity since most everything is closed except the rifle range.... so far. I've had no issues using the CCI #34 in place of regular Magnum primers. I can tell no difference in the reliability or performance of the CCI #34 compared to other Magnum large rifle primers I've tried- CCI 250, Winchester WLRM and Federal 215.

 

[sestoppelman]

My best loads for the .375 mag all used CCI 200 std LR primers. I use them primarily with ball powders which can be a bit hard to light at times. Or in a really big case. I like to load lighter than standard loads for some large caliber rifles for target work, and for those medium speed powders are used most often and standard primers.

 

[Dr Ray]

I figure that when you have a full/compressed load in a large cartridge then a magnum primer is required.
A fat spark is required and I use magnum primers in my 338 375 and 416.
I believe Winchester primers produce a fat spark primer so if using those then I assume you’ll be ok even with magnum cartridge loads.
I think the real issue is whether the powder is easy to ignite with copious quantities of powder.
I have had only one cartridge that failed to fire many years ago in 270.
I guess the magnum primers are used for magnum cartridges that have heaps of powder to burn.

 

[wswolf]

For the cartridges listed in the OP I would use magnum primers.

For smaller cartridges using ball powders magnum primers often give better accuracy. For instance my .220 Swift does much better with magnum primers when using 760, Hunter or Big Game.

Recently an '06 produced much better groups with Reloder 16 by switching from my usual 210s to 215s. Sometimes switching primers can be beneficial but magnums might increase pressure significantly so reduce powder charges and watch the chronograph.

Cheers