Primers for 327 Federal Magnum

R

Real Gun

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Speer advises using small rifle primers to reload 327 Federal Magnum in order to preclude "flowback". This cartridge can exceed 40k psi.

Yesterday I shot test loads for all four types of small primers, SP, SPM, SR, SRM. My 327 Federal Magnum load uses 12.0 gr AA#9 and 95 gr Penn LRNFP in fired cases.

I certainly thought I sensed a difference in the magnums, but without any science, it seemed to me that I would stick with Speer's instruction to use small rifle primers.

Small pistol seemed a bit soft, as if pressure was leaking or powder was not igniting, whatever. The magnums had a kick, and the small rifle seemed just right to me. For what it's worth.

BTW I was shooting a 4 5/8" Ruger Single Seven. I don't shoot well enough to judge any accuracy differences. I just wanted to know by feel, when the gun fires. I had no extraction issues, but then again the cylinder has been reamed with a $130 finishing reamer I had to buy to save the gun in lieu of Ruger wanting to just scrap the gun for lack of cylinders or repair capacity.

I forgot to mention that my SR were Winchester, while the rest were CCI.
 
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Stick with the standard SR primers. What a magnum primer does is increase the start pressure, which can increase powder burn rate and, with it, peak pressure, by decreasing the degree of expansion completed at the time the pressure peaks. That extra start pressure should not be required in the small .357 Federal's case volume. I've measured (Pressure Trace instrument) SRM primers raising peak pressure about 10% in the .223 Remington, and would expect they could do more than that in the small case volume you have.
 
I guess I should add that I don't intend to shoot soft loads, but if I did, I think the rationale for rifle primers would be lost, and regular small pistol primers would suffice. Shooting a softer load with a powder that would require Small Pistol Magnum primer detonation wouldn't make sense to me.
 
As I load for more than a dozen different chamberings, I find that I use a -LOT- of small pistol primers... I make and shoot a large volume of 9mm and .38 Special.

So sticking with the proper primer in .327 Federal (small rifle) is not only the right thing to do -- it makes use of a primer I stock anyway (for .30 Carbine and .223 Rem) and keeps me from eating in to my stock of small pistol primers that I use so many of already.

If we step back and compare the .327 Federal to the .30 Carbine -- we see how ballistically similar they are. They REALLY are. And using a small pistol primer in .30 Carbine is an equally bad idea.
 
I'm a newbie at the 327 Federal, and I'll have to admit that I'm still not fully clued in on primers. Since data on the 327 mag is still somewhat scarce, I've been scouring the internet. Brian Pearce says to use small pistol (not magnum) primers. The "official" reloading data (from Hodgdon and Speer) that I've been able to find say to use small pistol magnum primers (Federal 200). An article by John Taffin indicates that he used CCI 500 (small pistol) primers for his loads. Sevens and other knowledgeable reloaders on this forum say to use small rifle magnums. I consider all of the foregoing to be authoritative, but I'm confused by the divergence of opinion.

I've been using small pistol magnum (Winchester WSPM) in my SP101 for near-maximum loads using W296/H110 and CFEPistol, and I've had reasonably good results. I've also read that small pistol magnum and small rifle primers are the same, but I don't know if that's based on fact or conjecture.

Any ideas on why there is such a diversity of opinion?
 
JayCee,

Sevens just said in the post before yours that he is using small rifle, not small rifle magnum. You could use the latter, but you'll likely exceed standard pressures if you use that with a full load developed using a standard small rifle or a magnum pistol primer. Recently, in another thread, a ,member reported speaking with CCI, and they confirmed the priming mix and quantity is identical for the small pistol magnum and small rifle standard strength primers as is the cup thickness and they said their own employees just buy the small rifle standard primers for rifle and pistol, both. CCI small pistol magnum and small rifle standard primers are, according to their phone rep, the same thing packaged in different boxes.

The small pistol magnum and small rifle standard primer cup is nickel-plated brass about 0.020" thick. Rifle magnum uses 0.025" thick brass standard, which can defy the ability of some revolver firing pins to deliver enough energy for dependable ignition. Standard pistol primers, IIRC, usually have cups about 0.016" thick, but don't hold me to that number. I can't find my measurement info, which is about 25 years old in any case, and should be redone.

In any event, what you are looking to have in the .327 Fed is the best compromise between strength and reliable ignition. If you download for some wadcutters or other target and plinking loads, then a standard primer will do the job.


Real Gun,

The main thing is to realize that if you are feeling more recoil from the same powder charge, then you are reaching higher pressures. There's basically no other possibility the laws of physics allow for. If you have a chronograph, you can very roughly estimate the pressure difference indirectly by figuring out how much powder it would take to get the measured velocity increase with the same primer, and then what pressure increase that amount of powder would cause based on the exponential factor the ratio of the logarithms of the pressures in the start and maxi loads give you. Not entirely trivial, but possible. Not entirely accurate as it will tend to underestimate the pressure a little. And you do need the velocity data to make it work.
 
I shoot cast in my 327 BH and all i use is SP in it and I have no other gun that I need SR in so I will not spend the extra on some thing that I will not use in anything else.It works for me.
 
Stick with the standard SR primers. What a magnum primer does is increase the start pressure, which can increase powder burn rate and, with it, peak pressure, by decreasing the degree of expansion completed at the time the pressure peaks. That extra start pressure should not be required in the small .357 Federal's case volume. I've measured (Pressure Trace instrument) SRM primers raising peak pressure about 10% in the .223 Remington, and would expect they could do more than that in the small case volume you have.
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If we are saying that small pistol magnum and small rifle are the same primer, at least within a given brand, then maybe a better way of saying this is "not to use Small Rifle Magnums". Is there enough uniformity among vendors' primer specs to refer to primer types in generalities?
 
I shoot cast in my 327 BH and all i use is SP in it and I have no other gun that I need SR in so I will not spend the extra on some thing that I will not use in anything else.It works for me.
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It should be a concern for the upper end of the pressure limits (hot loads). You might be using a different bullet then or adding gas checks.
 
I can only speak to CCI brand primers and I have seen enough evidence direct from CCI/ATK to believe that small rifle and small pistol magnum are the same primer. In nearly three decades, I have not yet ever purchased a small pistol magnum primer and years ago I transitioned to the small rifle primer for slow burning powder magnum revolver rounds (.357 Magnum.)

Other brands? No idea and I have seen no evidence either way.
 
Real Gun said:
Is there enough uniformity among vendors' primer specs to refer to primer types in generalities?
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Unfortunately not. There was a good study in the Rifleman's Journal, showing tables of actual pressures and velocity differences produced by different rifle primers, but unfortunately German Salazar took it off line for general viewing. It was probably being linked to so often that the bandwidth cost became more than he wanted to pay for, but I'm not actually sure of his reasons.

About all you can say for sure is that magnum primers make more gas than standard primers of the same brand in order to increase start pressure, and that SRM's have the thickest small primer profile cups, SR's are next thickest and identical so SPM in at least the CCI case, and that SP primers have the thinnest cups. And so, as usual, the handloader gets to experiment to determine the specifics that apply to his gun, cartridge and component combination. A chronograph quickly tells you if one primer is producing higher peak pressure with your powder charge than another, by virtue of the higher mean velocity that results using the same charge of powder under the same bullet in the same cases. Occasionally you get a funny situation where a magnum primer produces lower pressure and velocity, which can happen for a couple of different reasons I've mentioned elsewhere. If it occurs for you, check the SD of the velocity. If that has worsened along with the velocity drop, you want to use a milder primer.
 
Excellent thread

As a new member ( this thread lead me to join ) and a recent purchaser of a SP 101, this thread was something missing from most reloading journals. My problem was which primer to use since the load data for the .327 is all over the place in regards to primers. Knowing now that the cci spm and sr are the same has put my mind at ease on loading this caliber. You guys are awesome!
 
For what it may be worth, I've done a bit of load development for the .327 Federal Magnum, and CCI regular small pistol primers were used throughout.
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Not a problem, until you get toward the maximum pressure end of the scale, the real magnums. In lieu of powders that require it, it's not about ignition but rather pressure.
 
Not a problem, until you get toward the maximum pressure end of the scale, the real magnums. In lieu of powders that require it, it's not about ignition but rather pressure.
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I'm not sure what the point is, but all other things equal, for any given propellant charge, peak chamber pressure will be lower if ignited by a non-magnum primer.

In all events, tests by people I trust conclude that magnum primers are never needed for AA#9, nor for any load with H110 in the .327 Federal Magnum.
 
RKG, the point is that ATK/Federal designed the .327 Federal Magnum to run at a 45k PSI max pressure and use a small rifle primer due to the fact that the round simply generates MORE pressure than most (typical) handguns rounds operate at. The small rifle primer isn't (necessarily?!) wanted or needed for it's hotter/long flame properties but rather for it's thicker, stronger primer cup.

As the .30 Carbine is extremely similar (and also spec'd for a small rifle primer) and runs at 40,000 PSI max, the .327 Federal running an even higher pressure is loaded with a small rifle primer.

There is only one of the big-name ammo producers that has EVER made factory .327 Federal ammo, and that is ATK/CCI/Speer. And they have only ever used a small rifle primer.

What Buffalo Bore chooses to use? Or you choose to use? Or what I choose to use? Or what Brian Pearce chooses to use? That is whatever it is, I suppose, but the original specification for the cartridge by the folks that created it and the only original source from full spec factory ammo... uses a small rifle primer.

As long as we can agree on that and understand why that is... going forward with out own plans is acceptable as long as we know the risks.

Heck, on the load data for .327 Federal thread, I have been doing a lot of testing with extremely oddball bullets that also goes way, WAY outside the original design spec of the cartridge. ;)
 
OK, I interpreted Real Gun's comment addressed to the magnum vs. non-magnum issue.

The small rifle vs. small pistol issue is addressed in Pearce's article in Handload #294, at pages 31, 34.
 
The small rifle vs. small pistol issue
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The issue is [small rifle] versus [small pistol magnum]. I don't think there can be much of a debate about whether small pistol is fine for loads that don't approach max pressure specs.
 
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