I wanted to share the results of some recent testing I did as I imagine some others may find this interesting as well.
I see a lot of people in shooting groups (primarily facebook groups) ask about using large rifle primers in cartridges that "should" use a magnum primer. They seem to get a range of varied responses, but most people cannot provide any data to support whatever stance they take on the matter. With primer availability what it is, it is certainly understandable that someone might entertain the option of using a LRP in a magnum cartridge such as 300 PRC. I actually did that very thing in 2022 for an elk load I was developing. On that hunt, I ended up shooting a cow elk on the coldest day of the trip and had zero issues with powder ignition. It was somewhere between 0F-10F that morning and the daytime high was somewhere in the mid-20's. A sample size of one is not significant data in my experience so I wanted to explore the issue further.
My inspiration for this testing comes from the video series done by Johnny's Reloading Bench where he investigated hang-fires/misfires in 6.5CM using SRP and LRP. His testing was methodical and I found it very informative.
Investigating Hang Fires in 6.5 Creedmoor
After spending a few hours watching the full video series by Johnny's Reloading Bench, I was convinced that the same concepts would apply to 30 caliber magnum cartridges. In his videos, he found that N550 was a very difficult powder to ignite in 6.5CM. For that reason, I chose to use N550 in my test as well.
One of the more intriguing points from the video series was that he did not find temperature to have a significant impact of ignition performance. Loads that ignited poorly at very cold temps also ignited very poorly at higher temps. For now, I am going to focus primarily on cold performance as those are the conditions I hunt in and the conditions where performance matters to me the most.
Given that I had never experienced any misfire or hang-fire problems in my 300 PRC ( or any other cartridge), I was skeptical how possible this really was. To learn more about this issue, I attempted to set up an experiment with the intention of causing cold temperature ignition issues in the 300 PRC. I assumed that a very poor case fill % would exacerbate ignition issues so I attempted to find a powder charge that provided 60-70% case fill. Using my N550 profile in GRT I found that a charge weight of 60.0gr would provide 70.9% case fills and was predicted to produce a MV of ~2520fps using a Hornady ELD-M 225gr with COAL set to 3.778". This felt like a reasonable starting place to look for ignition issues and would give me an opportunity to adjust powder charge down into the range of 60-70% case fill if required.
For primer selection, I was limited to what I had on hand. I chose to do all of this testing using CCI primers even though I did also have a few other brands. I will reserve testing with other brands for another experiment. I chose to shoot 3-shot groups using the CCI BR-2, CCI 200 LRP, and CCI 250 LRMP.
In addition to choosing all my load variables, I had to wait for appropriate weather conditions to provide the needed environmental factors that contribute to poor ignition. With the recent cold snap we are having here in Missouri providing us several night below 0F, conditions were perfect for doing some cold weather testing. For all testing, the rifle and ammo were soaked for at least an hour in outdoor ambient conditions.
I will use the term Hang-fire to describe any condition where there is a noticeable delay between primer strike and powder ignition.
I will use the term Misfire to describe any condition where the powder never ignites.
Test conditions:
All testing done in the temperature range of 0F-10F at 1132' elevation
Load Tested:
New Lapua Brass with 60gr of N550 and ELD-M with COAL @ 3.778"
Results:
CCI BR-2
2463fps Hang-fire
2421fps Hang-fire
2438fps Hang-fire
CCI 200 LRP
2399fps Hang-fire
Misfire
Misfire
CCI 250 LRMP
2470fps No ignition issues
2478fps No ignition issues
2441fps No ignition issues
I was very pleased to find that I was able to produce ignition issues with 60.0gr of N550. I wanted to make certain that the CCI 200 group was not a fluke so I chose to shoot one more three shot group using a brand new sleeve of CCI 200 LRP. That test produced nearly identical results as follows:
CCI 200 LRP
2444fps Hang-fire
2417fps Hang-fire
Misfire
After allowing the 3 total misfires to rest for an hour I carefully removed the bullets and primers. I found that all three primer pockets had black marks indicating that the primer did indeed ignite. After inspecting the powder in the misfired cartridges, there are a few granules that appear discolored but it is in the order of less than 5% of the total powder and none of the powder was clumped together. This is a very different result than what was observed in the videos by Johnny's Reloading Bench where much more powder appeared discolored.
Three misfires showing strong primer strike
At this point I was very curious if there was a way to demonstrate how case fill % affects ignition. I am personally one of those individuals that likes to see case fill above 95%. I debated if I should use a different powder to test this, but ultimately decided to use N550 and a case filler as I thought that would better demonstrate the impact of case fill % on ignition.
WARNING! DO NOT TRY THIS! THIS IS F*&^%ING DANGEROUS!!!! OVERPRESSURE IS VERY POSSIBLE!
I added 20gr of corn grits on top of the N550 which resulted in a case fill that was flush with the neck/shoulder junction. When the bullet was seated the boat tail would press down slightly on the corn grits and ensure that the N550 was firmly up against the primer pocket. This was my attempt to simulate how well N550 would ignite if it was possible to achieve 100% case fill.
Results:
2688fps OVERPRESSURE
2652fps OVERPRESSURE
I chose not to shoot the third round
Bolt lift was very significant with this load and I would not recommend anyone try this. I have never personally experienced overpressure with compressed loads, but I also don't normally put corn grits in my ammo either so I am sure that was a contributing factor. The major takeaway is that the loads with 100% case-fill did not have hang-fire or misfire issues like the same load at 70.9% case fill exhibited.
SUMMARY:
Firstly, the CCI 250 magnum primers does ignite in cold temperatures more reliably than the CCI BR-2 or CCI 200. It exhibited zero hang-fires or misfires in my testing, but that was with a load that I was trying to intentionally get to misfire by means of making a very poor powder selection. I.e.- powder was way too fast for cartridge and provided very low case fill (70.9% case fill). If N565 was used during this testing I think the results would have been much different, but that testing will be reserved for another day
If anyone is using primer selection alone as the only way that they are ensuring ignition at cold temperatures I think they are asking for trouble. If there is any variability in primer performance and you are shooting a load with low case fill, you may very well find yourself on the edge of acceptable ignition. Relying solely on the smallest and cheapest component in your ammo is not a recipe for success in my mind.
Secondly, by increasing case fill from 70.9% to 100%, misfires and hang-fires were eliminated. The way I chose to demonstrate this was not ideal (or safe), but it helps illustrate how important it is to have high load density (high case fill %) in cold weather. This is a small experiment with a small sample size, but is an experiment that I think can easily be replicated so I would encourage others to try this for yourself. I will be repeating this same test (not the corn grits part) with other powders and am very curious if I can identify a specific case fill % where ignition starts to become problematic.
For those that are unable to source large rifle magnum primers, I would simply say that your powder selection is very critical for shooting in cold weather. Make sure you are choosing powders that provide greater than 90% case fill and test it for yourself if you are concerned. I've done it myself with success so I know it's possible.
I see a lot of people in shooting groups (primarily facebook groups) ask about using large rifle primers in cartridges that "should" use a magnum primer. They seem to get a range of varied responses, but most people cannot provide any data to support whatever stance they take on the matter. With primer availability what it is, it is certainly understandable that someone might entertain the option of using a LRP in a magnum cartridge such as 300 PRC. I actually did that very thing in 2022 for an elk load I was developing. On that hunt, I ended up shooting a cow elk on the coldest day of the trip and had zero issues with powder ignition. It was somewhere between 0F-10F that morning and the daytime high was somewhere in the mid-20's. A sample size of one is not significant data in my experience so I wanted to explore the issue further.
My inspiration for this testing comes from the video series done by Johnny's Reloading Bench where he investigated hang-fires/misfires in 6.5CM using SRP and LRP. His testing was methodical and I found it very informative.
Investigating Hang Fires in 6.5 Creedmoor
After spending a few hours watching the full video series by Johnny's Reloading Bench, I was convinced that the same concepts would apply to 30 caliber magnum cartridges. In his videos, he found that N550 was a very difficult powder to ignite in 6.5CM. For that reason, I chose to use N550 in my test as well.
One of the more intriguing points from the video series was that he did not find temperature to have a significant impact of ignition performance. Loads that ignited poorly at very cold temps also ignited very poorly at higher temps. For now, I am going to focus primarily on cold performance as those are the conditions I hunt in and the conditions where performance matters to me the most.
Given that I had never experienced any misfire or hang-fire problems in my 300 PRC ( or any other cartridge), I was skeptical how possible this really was. To learn more about this issue, I attempted to set up an experiment with the intention of causing cold temperature ignition issues in the 300 PRC. I assumed that a very poor case fill % would exacerbate ignition issues so I attempted to find a powder charge that provided 60-70% case fill. Using my N550 profile in GRT I found that a charge weight of 60.0gr would provide 70.9% case fills and was predicted to produce a MV of ~2520fps using a Hornady ELD-M 225gr with COAL set to 3.778". This felt like a reasonable starting place to look for ignition issues and would give me an opportunity to adjust powder charge down into the range of 60-70% case fill if required.
For primer selection, I was limited to what I had on hand. I chose to do all of this testing using CCI primers even though I did also have a few other brands. I will reserve testing with other brands for another experiment. I chose to shoot 3-shot groups using the CCI BR-2, CCI 200 LRP, and CCI 250 LRMP.
In addition to choosing all my load variables, I had to wait for appropriate weather conditions to provide the needed environmental factors that contribute to poor ignition. With the recent cold snap we are having here in Missouri providing us several night below 0F, conditions were perfect for doing some cold weather testing. For all testing, the rifle and ammo were soaked for at least an hour in outdoor ambient conditions.
I will use the term Hang-fire to describe any condition where there is a noticeable delay between primer strike and powder ignition.
I will use the term Misfire to describe any condition where the powder never ignites.
Test conditions:
All testing done in the temperature range of 0F-10F at 1132' elevation
Load Tested:
New Lapua Brass with 60gr of N550 and ELD-M with COAL @ 3.778"
Results:
CCI BR-2
2463fps Hang-fire
2421fps Hang-fire
2438fps Hang-fire
CCI 200 LRP
2399fps Hang-fire
Misfire
Misfire
CCI 250 LRMP
2470fps No ignition issues
2478fps No ignition issues
2441fps No ignition issues
I was very pleased to find that I was able to produce ignition issues with 60.0gr of N550. I wanted to make certain that the CCI 200 group was not a fluke so I chose to shoot one more three shot group using a brand new sleeve of CCI 200 LRP. That test produced nearly identical results as follows:
CCI 200 LRP
2444fps Hang-fire
2417fps Hang-fire
Misfire
After allowing the 3 total misfires to rest for an hour I carefully removed the bullets and primers. I found that all three primer pockets had black marks indicating that the primer did indeed ignite. After inspecting the powder in the misfired cartridges, there are a few granules that appear discolored but it is in the order of less than 5% of the total powder and none of the powder was clumped together. This is a very different result than what was observed in the videos by Johnny's Reloading Bench where much more powder appeared discolored.
Three misfires showing strong primer strike
At this point I was very curious if there was a way to demonstrate how case fill % affects ignition. I am personally one of those individuals that likes to see case fill above 95%. I debated if I should use a different powder to test this, but ultimately decided to use N550 and a case filler as I thought that would better demonstrate the impact of case fill % on ignition.
WARNING! DO NOT TRY THIS! THIS IS F*&^%ING DANGEROUS!!!! OVERPRESSURE IS VERY POSSIBLE!
I added 20gr of corn grits on top of the N550 which resulted in a case fill that was flush with the neck/shoulder junction. When the bullet was seated the boat tail would press down slightly on the corn grits and ensure that the N550 was firmly up against the primer pocket. This was my attempt to simulate how well N550 would ignite if it was possible to achieve 100% case fill.
Results:
2688fps OVERPRESSURE
2652fps OVERPRESSURE
I chose not to shoot the third round
Bolt lift was very significant with this load and I would not recommend anyone try this. I have never personally experienced overpressure with compressed loads, but I also don't normally put corn grits in my ammo either so I am sure that was a contributing factor. The major takeaway is that the loads with 100% case-fill did not have hang-fire or misfire issues like the same load at 70.9% case fill exhibited.
SUMMARY:
Firstly, the CCI 250 magnum primers does ignite in cold temperatures more reliably than the CCI BR-2 or CCI 200. It exhibited zero hang-fires or misfires in my testing, but that was with a load that I was trying to intentionally get to misfire by means of making a very poor powder selection. I.e.- powder was way too fast for cartridge and provided very low case fill (70.9% case fill). If N565 was used during this testing I think the results would have been much different, but that testing will be reserved for another day
If anyone is using primer selection alone as the only way that they are ensuring ignition at cold temperatures I think they are asking for trouble. If there is any variability in primer performance and you are shooting a load with low case fill, you may very well find yourself on the edge of acceptable ignition. Relying solely on the smallest and cheapest component in your ammo is not a recipe for success in my mind.
Secondly, by increasing case fill from 70.9% to 100%, misfires and hang-fires were eliminated. The way I chose to demonstrate this was not ideal (or safe), but it helps illustrate how important it is to have high load density (high case fill %) in cold weather. This is a small experiment with a small sample size, but is an experiment that I think can easily be replicated so I would encourage others to try this for yourself. I will be repeating this same test (not the corn grits part) with other powders and am very curious if I can identify a specific case fill % where ignition starts to become problematic.
For those that are unable to source large rifle magnum primers, I would simply say that your powder selection is very critical for shooting in cold weather. Make sure you are choosing powders that provide greater than 90% case fill and test it for yourself if you are concerned. I've done it myself with success so I know it's possible.
Last edited:
memtb
