Standard vs. Magnum Small Pistol Primers: My Experience

[Landric]

A little while back I picked up some Winchester Small Pistol Magnum primers since I couldn't locate and standards. I loaded up some test rounds, half with standard primers and half with magnums, same powder charges, same brass, same bullets. I didn't have any overpressure signs with any of them. Here were my results (I have purposely left out powder charge weights):

.32 S&W Long, 100 grain RNFP, Trail Boss:

Ave Std. Primer: 570fps, Std. Deviation 18.08
Ave Mag Primer: 553fps, Std. Deviation 8.13

.32 H&R Magnum, 100 grain RNFP, AA#5:

Ave Std. Primer: 749fps, Std. Deviation 32.98
Ave Mag Primer: 798fps, Std. Deviation 12.11

.38 Special, 158 grain RNL, HS-6:

Ave Std. Primer: 884fps, Std. Deviation 30.27
Ave Mag Primer: 890fps, Std. Deviation 20.86

9x19mm, 130 grain FMJ, HS-6:

Ave Std. Primer: 990fps, Std. Deviation 20.79
Ave Mag Primer: 1043fps, Std. Deviation 19.70

9x19mm, 125 grain RNL, HS-6:

Ave Std. Primer: 1116fps, Std. Deviation 17.54
Ave Mag Primer: 1122fps, Std, Deviation 13.20

The only two loads that the magnum primers made any significant difference in where the 100 grain H&R Magnum and the 130 grain FMJ 9x19mm. The magnum primers seemed to be more consistent overall, though it generally didn't represent a huge change. I tested the magnums with my standard loads and the conclusion I came to is that it is safe to use magnums in place of standards in the loads I generally use. I'd test other cartridges and charge weights before using magnums in those loadings.

I'm happy with the results and I plan to use my magnum primers for the cartridges above.

 

[Remo-99]

By those results, it appears the biggest reduction in std deviation, was in the calibres with longer casings (per diameter), as the shorter 9x19mm had a reduction to a lesser extent.

 

[moosehunt]

Let's take this further. As Small Rifle primers became progressively more scarce, I happened to acquire some Small Rifle Magnum primers. I started some comparisons and found no significant differences regarding loads with either Small Rifle or Small Rifle Magnum primers. I'm referring to group size, placement on target, and fired case indicators. I'm now expanding my observations into Small Pistol primers with the same loads (because Small Rifle primers are not available and occasionally Small Pistol primers are--temporarily). So far--granted, limited testing--I'm finding very little significant differences. I'm getting ready to expand my experimentation to Large Pistol in replacement of Large Rifle primers,--I'll be more cautious here. Point is, we had best start to learn what will and will not work. I'm not looking to find best loads, but loads (primer uses) that will work. I think we had better start being prepared, no?

 

[Oyeboten]

Possibly...different Powders could have differing responses to Magnum verses Standard Primers?


Where...one Brand/kind of Powder would show only a small difference, possibly, another, owuld have a larger difference in pressure/fps?


I've wondered if Magmun Primers, and the right Powder, would allow truely optimum fps for various weight .38 Snubbie loadings...

 

[moosehunt]

You miss the point, Oyeboten. It is not a matter of maximum performance, but what will work when that's all you have available. Become prepared!

 

[Marlin 45 carbine]

I just found myself in the same situ, but different powders. I'll try a few 10% reduced loads w/the mag primers first. good info.

 

[Coltdriver]

The hazard with using pistol primers in a rifle is that the pistol primer cup is more easily pierced in a rifle because they are significantly thinner.

Be very careful. You start with a regular rifle load with a pistol primer and you definitely run the risk of hot gas flowing back up into your face or damaging your rifle bolt face.

Pistols see no where near the pressures routinely found in rifles, hence the thicker cups on rifle primers.

 

[rdhood]

Pistols see no where near the pressures routinely found in rifles, hence the thicker cups on rifle primers.

True, but some are not far off. Look at .40S&W pressures compared to 7.62x39 Russian or .308 Win. Relatively speaking, they are pretty close.

BTW, I have been using large magnum Pistol primers in place of large Pistol Primers for about two months. No problems for me so far.

 

[Coltdriver]

rdhood that is a great point and it is also a great reason for never using a magnum primer in something like a 40 S&W!

Rifle firing pins arguably have greater mass and hit harder. Thats another reason its relatively easy to pierce a pistol primer with a rifle.

 

[ChallengerT/A]

I've run into the same questions on Standard vs Mag primers because after a 30 year hiatus I'm getting back into reloading. My favorites have been and always will be 38 Specials and 357 mag loaded with 296 powder and mag primers so this info is from that view point but should be relative to just about any reloading for pistols. What I'm left with from the "old days" but still in excellent condition is Mag primers and fast powder.

Let's start with the different primers themselves. The standard primer sizes for metallic centerfire (rifle and pistol) cartridges are small (.175" diameter) and large (.210" diameter). The standard primer types are pistol, pistol magnum, rifle, and rifle magnum.
Rifle primers use tougher cups than pistol primers because the firing pin blow of rifles is usually harder than the firing pin blow of pistols. Rifle primers also contain more priming compound than pistol primers, since rifle cartridges typically contain more powder than pistol cartridges.
Magnum primers are "hotter" and burn longer than standard primers. CCI/Speer typically recommends that magnum primers be used with ball (or spherical) powders, when loading magnum or other large capacity cases, and when it is anticipated that the cartridges will be used at temperatures below 20 degrees F. Ball powders are generally harder to ignite than flake and extruded powders and magnum primers are often called for, even in non-magnum rifle and pistol cartridges. Let your reloading manual be your guide to primer selection.
Reference: http://www.cci-ammunition.com/products/primers.aspx

I would have to assume that the pressure difference occur because of the powder compound in the rifle primers. I am not recommending their use but Vihtavuori did use the small rifle primers in their powder testing for the 357 Mag. Also with the tougher caps of the rifle primers you at least would need a full fall hammer of a revolver with full strength main spring to strike them properly.

So keeping this to just the small pistol primers, standard vs magnum, what is usable? I concluded that they should be completely interchangeable as long as you start with the lowest starting load recommended for the powder.

In comparing data I used the Speer reloading Manual #14 and The Complete Reloading Manual for the .357 Magnum that has 2,148 test load, 82 various bullet designs and 55 different powders just for the 357 Mag, along with many different websites.

In the tests run by Sierra, Nosler, Hornady, Lyman, Hodgdon, Alliant, IMR and Winchester they ALL used small pistol Magnum primers. Speer and RCBS use different primers depending on the powder. Accurate tested only with standard primers and as noted earlier Vihtavuori used small rifle primers.

It's said that Magnum primers should be used only on Magnum cartridges but it's always been my understanding that it depends on the rate of burn of the powder used but even that isn't completely true because Alliant tested Bullseye, a fast powder, with Mag primers. Powder Burn Rates.

Most of the Ball Powders are slower burning, 296, H110, IMR4227 and HS7 but there are others in that burn range, see the link above. Also Winchester tested its faster burning 231 with Mag primers so you'll maybe need to do some web searching to find a good starting load. Since Landric has posted some very good first hand data, I personally would start my loading with the lowest listing for standard primers and sub the Mags. In a MODERN handgun I would not expect to see any problem.

I would also not load a cast lead bullet at more than about 1000 ft/sec to help prevent leading and I wouldn't load a jacketed bullet less than 750 ft/sec to guarantee expulsion from the barrel. At lower velocities on the jacketed bullets there have been instances where the lead has left the jacket in the forcing cone and/or in the barrel.

 

[evan price]

I've loaded small rifle primers in small-primer pistol brass to good effect. I've had the same experience vis-a-vis using magnum primers where standard would normally be all that is required.

I would *NOT* load large rifle brass with large pistol primers. First, the pistol primers are shorter and you may not get enough firing pin protrusion to correctly light them off. Second, the pistol primers are thinner than rifle primers and for a high pressure rifle application it's not a good idea. It doesn't matter if a pistol is "almost" as high pressure as a rifle- that almost isn't good enough! IN a time of great desparation, maybe, but not for the sake of the current situation with primers being scarce. It's not TEOTWAWKI yet!

Furthermore, loading large rifle primers in pistol brass that is not intended for rifle primers could cause problems due to the increased height of a rifle primer protruding above the case head of the brass. In a revolver this could lock up the cylinder and in a semiauto it could cause rounds to not chamber properly.

Please note the italicized caveat- I am aware that there are cases that specify rifle primers (the large Magnums) and it is possible to bore the primer pocket deeper, permanantly modifying the brass for large rifle primers.

 

[Redneck with a 40]

I've been loading .308 ammo for my dad's FN-AR, with AA 2520 powder and standard primers. The initial results were horrible, 6" group at 100 yards. We decided to try magnum primers and the groups tightened down to 1.5", everything else being the same, wow. I do believe that in medium and large capacity rifle cases, with slow burning ball powders, magnum primers are much better, much more consistent ignition. We're runnin' 44 grains of AA 2520 behind a Nosler 168 gr HPBT, federal brass.

 

[Doug b]

Redneck with a 40 that's been my experience to working with .223 and H335. Doing parallel loads changing only the primer,20 rnd groups went from 3" vertically strung with a standard small rifle primer to " were ever you put the cross hairs thats were the bullet went" with a mag primer and I'm talking well under 1" @100 yrds.

Now I'm working with 22 hornet and W296 and smr primers and getting the same kind of results.2'' and 3'' groups reduced to touching bullet holes @100 yrds. by going to a mag. primer.These were only 5 rnd. groups though.

Ball powder imho needs a mag prime.My next step will be 30-06 and ..........

 

[Kevin5098]

How many rounds of each load were fired?

 

[Redneck with a 40]

If that question is aimed at me Kevin, the answer is 12 of each. 6" groups with standard primers, 1.5" groups with magnum primers.

 

[claphoto]

I have lately been using large pistol primers in place of large pistol magnum primers for the same reason. (had to buy what was available) in .44 magnum loads. By golly they still go bang! Accuracy is still great, and barrels are still clean. I shoot the same loads in a wheel gun and a carbine. YES! we will find what works!

 

[Kevin5098]

Sorry Red, the question on number of rounds was for Landric. The statistician in me can't help but want to run some more statistics on his data.

 

[Landric]

Twelve rounds of each with the magnum primers. The standard primer loads are my usuals, so I've shot thousands of those.

 

[Kevin5098]

FWIW, the 32 S&W Long showed a small but statistically significant difference with magnum primers yielding lower velocities:

Two-Sample T-Test and CI

Sample N Mean StDev SE Mean
1 12 570.0 18.1 5.2
2 12 553.00 8.03 2.3


Difference = mu (1) - mu (2)
Estimate for difference: 17.00
95% CI for difference: (4.83, 29.17)
T-Test of difference = 0 (vs not =): T-Value = 2.98 P-Value = 0.009 DF = 15

Kevin

 

[ArchAngelCD]

Landric,
Thanks for posting your data but it didn't surprise me at all.

I always laugh a little when someone tells a reloader how they will have to drop the charge "way down" when switching to a Magnum primer instead of a standard primer. They warn of major over pressure problems if they don't.

BTW, I'm a little surprised the SD numbers didn't drop more with the Magnum primer when used with HS-6. I've found HS-6 performs better with Magnum primers because it's hard to ignite. I've gotten low single digit SD numbers in .38 Special +P rounds and a 158gr LSWC/HP bullet using HS-6 with a Magnum primer.

Again, thanks for sharing the data...

 

[bonza]

It used to be that Winchester used to recommend a magnum primer be used with their ball powders.....I don't see that anymore, what changed?

 

[moosehunt]

Bonza--I think I'd like to meet your Mom!!! How mean is that ocelot?

 

[ArchAngelCD]

It used to be that Winchester used to recommend a magnum primer be used with their ball powders.....I don't see that anymore, what changed?

bonza,
I don't know what changed but you are correct, my older manuals listed a Magnum primer for HS-5, HS-6 and HS-7. That's the reason I tried a Magnum primer with HS-6 and HS-7. I guess they are too lazy now to add the asterisk and footnote mentioning the Magnum primer.