Magnum Primers with Compressed Charges in Non-Magnum Cartridges

[South Pender]

Magnum primers are often recommended for use with ball powders in standard, non-magnum cartridges. I get this; the space between the kernels (spheres) is less than with extruded powders, and a more forceful primer is needed to ignite the whole powder column.

However, with extruded powders that are compressed (for example, a 105% capacity load) in standard cartridges, like the .270 Win. or 6.5x55 Swede, this compression will presumably reduce the space between the stick kernels. In this case, are magnum primers called for?

 

[Evanguy]

I would say no not normally, but if you wanted to you could start a little low and work your way up using magnum primers.

personally I use them in everything. I need them for some of my big bores and they work fine in my smaller bores so it allows me to stock pile one type.

although I though it was about how easy extruded powders are to light compared to ball powder, the irregular shape causes hot spots so it begins lighting faster then something the disperses the heat over the whole object. ball powder is still had to light even when you only have a half case of it

 

[B]

Ball powder has more deterrent compared to extruded powders. Airspace around compressed charges is not a reason I have ever heard used for choosing Magnum over standard. I also just use Magnum primers for all my loading. ES/SD is almost always significantly lower and accuracy is of course generally better because of that.

 

[Potashminer]

Magnum primers are often recommended for use with ball powders in standard, non-magnum cartridges. I get this; the space between the kernels (spheres) is less than with extruded powders, and a more forceful primer is needed to ignite the whole powder column.

However, with extruded powders that are compressed (for example, a 105% capacity load) in standard cartridges, like the .270 Win. or 6.5x55 Swede, this compression will presumably reduce the space between the stick kernels. In this case, are magnum primers called for?

You could be correct, but is different than what I understood - I thought ball powders had various deterrents added to manage their burning rate - which meant the ball type was harder to ignite than the "log" type - needed more heat / flame. As mentioned, I could be mislead about that. I am quite certain I read that the larger powders manage that burning rate with holes through the log, and other physical characteristics, to control the speed of the burn ...

 

[Meroh]

I would say no not normally, but if you wanted to you could start a little low and work your way up using magnum primers.

personally I use them in everything. I need them for some of my big bores and they work fine in my smaller bores so it allows me to stock pile one type.

although I though it was about how easy extruded powders are to light compared to ball powder, the irregular shape causes hot spots so it begins lighting faster then something the disperses the heat over the whole object. ball powder is still had to light even when you only have a half case of it

I use them all the time in 6.5 x 55; in compressed loads over compressed Dominion 4350 SC powder. Why? I have read in a number of articles that it increases the temperature stability of powders. It does not hurt. Start one grain lower and work your way up.

 

[Potashminer]

From wherever, I was "under the impression" that magnum primers were preferred for ball powders, for larger volume cases like with belts, and for more dependable cold weather (minus 20 C type of cold) ignition. Is actually sort of surprising to me to hear people commonly use them for everything - regardless of powder type, case volume or temperature - but also pretty consistent that has to be worked up separately, than a loading done with a "normal" primer.

 

[Evanguy]

That is what they were designed for

I started using magnum primers when i was shooting cast bullets in my 303's using a few gr of w231 and then in all my cast relaoding and after that in all my cases that fit LRP no matter what im loading (cast or jacketed, low or high pressure, 3gr or 100gr, ball or extruded)

 

[mbogo3]

I use magnum primers in all my loads but cast.

 

[Andy]

My understanding of powders is that:

1. the highest surface area for a given volume (weight) of powder is the "flake", followed by "extruded" (log-shape), and the lowest is "spherical". Hence the shape that inherently has the fastest burn rate is flake, which is what we typically see in pistol and shotgun powders and rarely (nowadays) in rifle powders. Spherical would be inherently the slowest to burn for a given volume;
2. burn rate is further influenced by the powder's composition, the addition of burn deterrents, and modificatons to the shape such as holes, indentations, etc.; and
3. the spherical shape tends to pack most tightly in a cartridge, particularly with very small spheres, and hence the room for air (and for the flame to travel) is reduced over other shapes. Compression further reduces that.

"Magnum" primers can assist in getting the burn initiated when conditions are not favourable, such as lack of air-space, cold weather, large payloads, etc.

 

[nitro-express]

At the core it's an ignition issue. In cold weather powder gets a bit harder to ignite, and could need a hotter primer. More powder requires more primer, makes sense. Ball powders by their very nature can sometimes need more primer.

Bottom line, the only test I know of is to chronograph the load and see if there are ignition issues. Not all primers are the same, there are differences in brisance. Some primers are more magnum than others. Some primers do a better job of igniting ball powders.

Before buying a chronograph I just used more primer than I thought was required just to be safe. That is not the best approach, too much primer has it's issues as well.

Unless unavoidable, I avoid compressed loads. Back in the day I used H870 in the 7mm RM, drop tube and compressed, worked well. Always with a F215.

Nitro

 

[bearhunter]

I use them all the time in 6.5 x 55; in compressed loads over compressed Dominion 4350 SC powder. Why? I have read in a number of articles that it increases the temperature stability of powders. It does not hurt. Start one grain lower and work your way up.

This,

I use magnum primers for everything and have for fourty years.

As Meroh says, use a bit of common sense, one grain of powder isn't going to make enough difference for most chronies to detect, unless it's a small capacity case.

 

[South Pender]

My understanding of powders is that:
...
3. the spherical shape tends to pack most tightly in a cartridge, particularly with very small spheres, and hence the room for air is reduced over other shapes. Compression further reduces that.

This is the phenomenon that got me wondering about tightly-compressed charges of extruded powders.

 

[BigUglyMan]

I grew up using magnum primers in standard cases for years because we did a lot of hunting in sub-zero (significantly) and I remember at least one of the Old Man's handloads in the 30-06 used 760 which was probably another driver behind it. Not sure if it will make a lot of difference, but if I was hunting in the cold I would probably still use the magnum primer.

 

[CzyHorse]

I either read or was told by my mentor once you exceed 60 grains in a rifle case, it's time to think about a magnum primer.

IMO, for the same reason Engineer's require fill to be installed and compacted lifts. It's a more important to have consistent compression thru the powder column. I'm an Environmental Civil Engineering Technologist.

My recent experience with compressed loads in my 444Marlin using LRP, N130 and 265gn FN Hornady bullets has me using a 20" 'powder drop tube' to get a more consistent compression thru the powder column. I made a powder drop tube with an old arrow shaft.

Before I started using the powder drop tube, I was having a lot of issues with the rifle jamming. Even with a heavy crimp, the bullet was jumping the crimp from the combined force of the powder pushing on the bullet and the heavy recoil. Top end loads with N130 & 265gn bullet are over 2400fps.
Once I started using the powder drop tube, I no longer had issues with bullets jumping the crimp under the heaviest recoil. The 2280fps accuracy node I settled on has an SD under 10.