Brian Pearce wrote an excellent article for this month's Handloader Magazine. He tested 300 loads for the 308 Winchester and had a very interesting finding when switching to magnum primers. He reported that magnum primers raised pressure by more than 3,000psi in equal loads.
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Magnum Primers in Standard Cartridges
- Thread starter GeauxTide
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They can also lower pressure. It depends on how the maker formulated the primer to make the additional gas a magnum primer needs to produce.
When there is a pressure increase like that, it is accompanied by a velocity increase, making it easy for someone with a chronograph to detect the change.
Incidentally, this article by Allan Jones on the subject mentions that magnum primers in standard cases often improve the ignition consistency of charges that don't fill the case well. The extra leftover space needs extra pressurizing for consistent ignition.
When there is a pressure increase like that, it is accompanied by a velocity increase, making it easy for someone with a chronograph to detect the change.
Incidentally, this article by Allan Jones on the subject mentions that magnum primers in standard cases often improve the ignition consistency of charges that don't fill the case well. The extra leftover space needs extra pressurizing for consistent ignition.
I don't think anyone would be surprised by that finding. Shooters have long used magnum primers in standard cartridges. Quite often reporting better accuracy. And sometimes slightly more speed. I don't know how much difference 3000 psi makes in velocity. I'd expect it would mean enough speed to measure, but unless someone is already pushing the envelope above book loads probably not enough to make a load dangerous.
He reported negligible increase in velocity in several loads.When there is a pressure increase like that, it is accompanied by a velocity increase, making it easy for someone with a chronograph to detect the change.
reynolds357
New member
Magnum primers vs std primers has more to do with the burn rate of the powder being used than it has to do with the size of the case.
Marco Califo
New member
Actually, it is the TYPE of powder. Ball powders need magnum primers for best ignition. 5.56 use WC844 (H-335) and 7.62 uses WC846 (H-BLC2). These ball powder require magnum primers for best ignition and the mil-spec primers (CCI #41 and #34) are "magnum" for this reason. CCI reworked their priming compounds to meet ball powder requirements. They also have thicker cups (less sensitive).
Magnum calibers require magnum primers.
Standard calibers may need magnum primers when using ball type powders.
But in a pinch, standard primers will still certainly go bang.
Here is a good explanation, including text from CCI:
https://www.ar15.com/forums/armory/...cessary_for_ball_powders_/42-405538/#i3794634
Magnum calibers require magnum primers.
Standard calibers may need magnum primers when using ball type powders.
But in a pinch, standard primers will still certainly go bang.
Here is a good explanation, including text from CCI:
https://www.ar15.com/forums/armory/...cessary_for_ball_powders_/42-405538/#i3794634
It's both. All a magnum primer needs to do to meet the definition is make more gas than a standard primer. If you read the Allan Jones article, you will learn CCI reformulated its magnum primers in '89 specifically to better ignite the highly deterrent-coated St. Marks ball powders. Not mentioned is that this was accomplished by adding hot spark making ingredients, like copper and zinc and barium compounds.
Back when German Salazar still had his Rifleman's Journal open to the public, there were some good photos of primer flames showing old magnum primers did not create the shower of white sparks the modern domestic ones do (the Russian magnum primers still don't; Tula and Wolf). However, the spark shower is apart from the fact all magnum primers make more gas for bigger spaces and hot spark making was developed after that. The reason for more gas is that moderate to high deterrent-coated powders can extinguish if the heat and pressure are not high enough to support a good start to spreading ignition. In the larger magnum cases, there is greater total air space between grains than a smaller capacity case has, so it takes more gas to reach a given pressure. However, if you take even a medium capacity case and fill it poorly, say to 75%, then it may have as much unfilled air space as a magnum version of itself does with 100% fill. In that case, a magnum primer can lower velocity SD and improve accuracy.
As an example, at the CMP forum a few years ago a fellow shooting low case-fill Garand loads in the roomy .30-06 reported disappointment with his group size and larger velocity SD than he wanted. I suggested he switch to CCI #34 primers and he reported back that they took his groups diameters down significantly and he was very happy with it. It's important to know the .30-06 case isn't just roomy, but that loads of 4895 commonly used in the old Garands these days only fill cases around 80%, so there's some extra room in there.
Back when German Salazar still had his Rifleman's Journal open to the public, there were some good photos of primer flames showing old magnum primers did not create the shower of white sparks the modern domestic ones do (the Russian magnum primers still don't; Tula and Wolf). However, the spark shower is apart from the fact all magnum primers make more gas for bigger spaces and hot spark making was developed after that. The reason for more gas is that moderate to high deterrent-coated powders can extinguish if the heat and pressure are not high enough to support a good start to spreading ignition. In the larger magnum cases, there is greater total air space between grains than a smaller capacity case has, so it takes more gas to reach a given pressure. However, if you take even a medium capacity case and fill it poorly, say to 75%, then it may have as much unfilled air space as a magnum version of itself does with 100% fill. In that case, a magnum primer can lower velocity SD and improve accuracy.
As an example, at the CMP forum a few years ago a fellow shooting low case-fill Garand loads in the roomy .30-06 reported disappointment with his group size and larger velocity SD than he wanted. I suggested he switch to CCI #34 primers and he reported back that they took his groups diameters down significantly and he was very happy with it. It's important to know the .30-06 case isn't just roomy, but that loads of 4895 commonly used in the old Garands these days only fill cases around 80%, so there's some extra room in there.
For the powders/loads Mr. Pierce actually pressure tested. While possible, would not necessarily mean that happens in all/most loads.
Am using mag primers with 748 for most loads, due to the increased accuracy I personally experienced. Same with AA-7 in most pistol loads am using it for.
Awhile back Fed 215's were supposedly the hottest, but believe CCI 34's now surpass them. That would strictly be guessing.
Am using mag primers with 748 for most loads, due to the increased accuracy I personally experienced. Same with AA-7 in most pistol loads am using it for.
Awhile back Fed 215's were supposedly the hottest, but believe CCI 34's now surpass them. That would strictly be guessing.
Zeke,
When I called CCI a few years back, they told me the priming mix charge in the #34 was identical to that in the CCI 250. So was cup thickness. The only difference was the angle of the anvil feet from the center being shallower to reduce sensitivity to meet military specs.
When I called CCI a few years back, they told me the priming mix charge in the #34 was identical to that in the CCI 250. So was cup thickness. The only difference was the angle of the anvil feet from the center being shallower to reduce sensitivity to meet military specs.
To add to Unclenick's post I saved a copy of my email from CCI. Here is the response:
Also from our friends at 6mm Bench Rest some photographs of primer flash.
Ron
Ron, here are the differences in the 2 primers. So the anvil angle change is the difference, this keeps the free floating firing pins from causing slam-fires in AR style platforms. This does make it so that a light strike will have a less of a change of going off.
CCI-250............................ Magnum primer, Mag primer mix, thick cup, standard anvil.
#34/7.62MM................... Mil. Spec. primer, thick cup, magnum primer charge, angle of anvil change.
Also from our friends at 6mm Bench Rest some photographs of primer flash.
Ron
Federal/CCI are owned by same company and from what I understand Fed is making #41 primer.
I really don't think it's any secret that they used Mag mix on #34/41 primer.
http://www.cci-ammunition.com/products/primers/primer_chart.htm It's down bottom of page.
This is another test on Primers
http://www.btgresearch.org/High-speed measurement of rifle primer blast waves.pdf
I really don't think it's any secret that they used Mag mix on #34/41 primer.
http://www.cci-ammunition.com/products/primers/primer_chart.htm It's down bottom of page.
This is another test on Primers
http://www.btgresearch.org/High-speed measurement of rifle primer blast waves.pdf
I had 3 CCI small rifle primers and was curious about what the difference was between them. These were all once fired Hornady 223R brass with CFE223, trickled up on a RCBS 505. Based on this, I standardized on #400 SRP for my rifle. Other powders or rifles this may not hold true.
Hornady 55 Gr FB-SP Hornady 55 Gr FB-SP Hornady 55 Gr FB-SP
2.206 ±.005 OAL 2.206 ±.005 OAL 2.206 ±.005 OAL
CCI #41 NATO primers CCI #450 SRMP CCI #400 SRP
Series No 3 Series No 4 Series No 2
Total number of shots 10 Total number of shots 10 Total number of shots 10
Stats - Average 2862.72 fps Stats - Average 2833.55 fps Stats - Average 2844.13 fps
Stats - Highest 2904.84 fps Stats - Highest 2903.3 fps Stats - Highest 2882.47 fps
Stats - Lowest 2800.34 fps Stats - Lowest 2780.51 fps Stats - Lowest 2806.38 fps
Stats - Ext. Spread 104.49 Stats - Ext. Spread 122.8 Stats - Ext. Spread 76.09
Stats - Std. Dev 40.15 fps Stats - Std. Dev 33.12 fps Stats - Std. Dev 24.41 fps
Well the spacing really got messed up when I posted, but bottom line, the #400 standard primers were only 18FPS slower than the #41, and had the lowest extreme spread and SD of the three.
Hornady 55 Gr FB-SP Hornady 55 Gr FB-SP Hornady 55 Gr FB-SP
2.206 ±.005 OAL 2.206 ±.005 OAL 2.206 ±.005 OAL
CCI #41 NATO primers CCI #450 SRMP CCI #400 SRP
Series No 3 Series No 4 Series No 2
Total number of shots 10 Total number of shots 10 Total number of shots 10
Stats - Average 2862.72 fps Stats - Average 2833.55 fps Stats - Average 2844.13 fps
Stats - Highest 2904.84 fps Stats - Highest 2903.3 fps Stats - Highest 2882.47 fps
Stats - Lowest 2800.34 fps Stats - Lowest 2780.51 fps Stats - Lowest 2806.38 fps
Stats - Ext. Spread 104.49 Stats - Ext. Spread 122.8 Stats - Ext. Spread 76.09
Stats - Std. Dev 40.15 fps Stats - Std. Dev 33.12 fps Stats - Std. Dev 24.41 fps
Well the spacing really got messed up when I posted, but bottom line, the #400 standard primers were only 18FPS slower than the #41, and had the lowest extreme spread and SD of the three.
In, IIRC, 2006, Charles Petty had a series of articles on testing components, including primers, in a .223 Remington Cooper Phoenix. He was using a 55-grain A-max and 24 grains of Reloader 10X in all the primer tests, IIRC. I forget whose brass it was. He got velocity ranging from 3150 fps with his mildest primer (Federal 205, I think), and 3000 fps from the warmest magnum primer (I've forgotten which one it was).
If finally got to read Pearce's article on .308 loads. In the larger capacity cases, the velocity difference is typically smaller. If I simulate Pearce's 3000 fps pressure increase in QuickLOAD, using the start pressure over a load 4895 with a 168-grain match bullet, I get only about 20 fps increase. It's not a lot, but it is measurable. However, what is more interesting is Pearce's description of increasing peak pressure with a Federal 215, but getting a muzzle velocity drop. What explains this is the higher peak pressure accelerating the bullet early enough in travel (the peak occurs within an inch or two of the throat) that the expansion rate became too great for the powder choice to make gas fast enough to keep up, so late-barrel pressure and post-peak acceleration dropped. It's an example of how this stuff can fool and, under some circumstances, be counterintuitive. The main point I would make is to watch out for velocity changes (in either direction) as an indicator ignition and pressure have changed and then, of course, keep watching for pressure signs.
If finally got to read Pearce's article on .308 loads. In the larger capacity cases, the velocity difference is typically smaller. If I simulate Pearce's 3000 fps pressure increase in QuickLOAD, using the start pressure over a load 4895 with a 168-grain match bullet, I get only about 20 fps increase. It's not a lot, but it is measurable. However, what is more interesting is Pearce's description of increasing peak pressure with a Federal 215, but getting a muzzle velocity drop. What explains this is the higher peak pressure accelerating the bullet early enough in travel (the peak occurs within an inch or two of the throat) that the expansion rate became too great for the powder choice to make gas fast enough to keep up, so late-barrel pressure and post-peak acceleration dropped. It's an example of how this stuff can fool and, under some circumstances, be counterintuitive. The main point I would make is to watch out for velocity changes (in either direction) as an indicator ignition and pressure have changed and then, of course, keep watching for pressure signs.
Actually, it is the TYPE of powder. Ball powders need magnum primers for best ignition. 5.56 use WC844 (H-335) and 7.62 uses WC846 (H-BLC2). These ball powder require magnum primers for best ignition and the mil-spec primers (CCI #41 and #34) are "magnum" for this reason. CCI reworked their priming compounds to meet ball powder requirements. They also have thicker cups (less sensitive).
I recently began to use some TAC I had left when I was shooting 223.
According to Ramshot, modern ball powders do not require magnum primers.
No issue using them, can play with and see if it helps accuracy of course, but not needed for ignition.
I don't know about W 748 or other mfg ball powders.
I find it odd that these pressure increases do not seem to translate to higher muzzle velocities during real world testing and in many if not most cases the use of a magnum primer leads to lower velocities. I have also read that certain powders perform better with certain primers
http://www.rifleshootermag.com/reloading/magnum-primers-for-non-magnum-loads/
http://www.targetshooter.co.uk/?p=2662
http://www.targetshooter.co.uk/?p=1471
They do seem to have a impact on SD's however. This week I am running a test on primer tests on one of my favorite loads. Nothing as extensive as Laurie Hollands tests above but 4 sets of ten rounds each using CC1 400, Rem 7 1/2, Fed GM Match, and CCI 450's. I will post the chrono results and targets. I am more interested in SD and group size. Since the load is a slow poke (2700 FPS) load almost a full 3 gn's below maximum I am not worried about over pressure
http://www.rifleshootermag.com/reloading/magnum-primers-for-non-magnum-loads/
http://www.targetshooter.co.uk/?p=2662
http://www.targetshooter.co.uk/?p=1471
They do seem to have a impact on SD's however. This week I am running a test on primer tests on one of my favorite loads. Nothing as extensive as Laurie Hollands tests above but 4 sets of ten rounds each using CC1 400, Rem 7 1/2, Fed GM Match, and CCI 450's. I will post the chrono results and targets. I am more interested in SD and group size. Since the load is a slow poke (2700 FPS) load almost a full 3 gn's below maximum I am not worried about over pressure