Brother in law called and asked if I have any use for a brick of magnum brimers. I don't but thought I'd ask here. Do these have any use in the single shot black powder / smokeless games we play ? He was traveling at the time but 95%+ sure they are Winchester. Can they be shipped thru normal channels?

Primers by law have to be shipped hazmat.

I use mag primers in my 32-40 and 28-35 with 300mp and when I used 4227, they give me better ignition. 

My dad is still using them in his 45-70 black powder.  That was the main line of thinking from the 90's

I use them with Goex Fg powder.  I have some of that left over from a long time ago.  That lot of powder won't shoot well for me unless I use magnum primers.

Chris

I use Rifle Magnum primers with Swiss FFFg in .38-50 Remington Hepburn, .40-60 Maynard, .40-65 and .45-70.

The hotter primer helps burn off fouling and improves accuracy.

I also place a newspaper wad inside the case over the flash hole exit to prevent BP packing in the channel resulting in a fuse effect resulting in variations in timing of ignition which affect accuracy.

First.... thanks to those who shared their experience using Magnum primers with 300MP, that's Definitely worth knowing..!

Yo Dave,

Thanks for this observation "regarding, over the flash hole exit to prevent BP packing in the channel resulting in a fuse effect resulting in variations in timing of ignition which affect accuracy.

Back when I was keeping good records and experimenting with all the variables I could think of I was shooting a 45-70  
Swiss  1 & 1/2 F, .1 compression, drop tubed from a 30" up. 

The rifle was essentially locked in a rest to reduce shooter error and  chronographed 

I got my best Extreme Spread and Standard Deviation numbers using a news print disk over primer as well. But my best numbers were achieved shooting Large PISTOL Primers.

I experimented with Large Rifle, Large rifle Magnum, standard and match primers.

I was under the impression, perhaps wrongly so, that the pistol primers, with their reduced brisance, was less disruptive to the powder column consistency which in turn resulted in a more even flame propagation from the base of the case towards the projectile. 

From the depths of my degrading memory there were several studies on primers that included not only flame patterns but the force / pressure on the powder column. If someone has a index of articles in PS / Precision Shooting magazine I think you might find the treatise defining the parameters of that study. 

"regarding, over the flash hole exit to prevent BP packing in the channel resulting in a fuse effect resulting in variations in timing of ignition which affect accuracy.

I had not heard of any studies where this was explored, although it would be an interesting rabbit hole to investigate. 

One avenue which might be worth researching would be to take the Pistol primer vs. LR Magnum question to the next level would be to shoot Black Powder using small rifle or small pistol primers. 

Years ago one enterprising individual developed steel sleeves which when pressed in a Large Rifle Primer pocket, it enabled the use of a small rifle or small pistol primer in a other wise large rifle cartridge.
As to reduced fouling with magnum primers, I think most of us wipe between shots when shooting Black.

Unfortunately I live in a condo, a community which frowns on shooting off my patio. So it's time to set up a 'GoFund Me' account so I can buy a farm from which I can perform all the experiments fellow ASSRA members want me to perfor

Thanks Mike.

All my primer evals were done with black powder..!
I appreciate the opinions and observations of others.
Certainly helps..

For me, Without all the other related qualifiers like neck tension, crimp type, bullet jump or jamb, full length sizing etc. etc. it's hard to sort out the benefits of one type of primer vs. the other.

Not everyone chronos so that would be good info.

THANKS


4570mike wrote on Jun 20^th, 2026 at 5:04pm:

FWITW , 
The following link is to Primer Power factor that was done by an individual

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Hypo5.0 wrote on Jun 21^st, 2026 at 10:57am:

Good observations  Rick,.. I'll check my saved editions .

"Audette developed a method to determine the “sweet spot” for a given rifle by varying the powder charge. He referred to this method as the Incremental Load Development Method, (ILDM). He would typically load a series of 20 different powder charges while using the same bullet, primer, case brand, and overall length. The powder charge increment was small (remember this was smokeless powder), 0.2 or 0.3 grains."

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AKA the Ladder test. 
burntwater wrote on Jun 21^st, 2026 at 4:39pm:


RJ