9mm; SP and SR primers
The last few months there have been several threads regards the use of SP magnum and/or SR primers in the 9mm cartridge. I had conducted a test of SP and SR primers in the 357 Magnum and posted the results [https://castboolits.gunloads.com/sho...he-357-Magnum]. In that cartridge with Unique powder there was enough evidence demonstrating the SP Magnum and SR primers could raise the psi enough to warrant caution in doing so.
However, does that correspond to the 9mm cartridge which was the subject of the question. Some definitely thought the substitution should not be made. Others were adamant that using a SP Magnum or SR primer in the 9mm with a given load posed no problem. A video showing a limited test by a commercial reloader demonstrated no different in pressure or velocity. Others stated they found little variance in chronographed velocity as proof there was no difference in psi. I proposed caution be used should it be necessary to substitute SP Magnum or SR primers in the 9mm with a given load.
I have just completed 3 additional more fairly comprehensive pressure/velocity tests of 3 different powders [Bullseye, VV 3N37 and HS-6] in the 9mm cartridge.
A commercial loader request I test the 9mm cartridge with CCI’s 500, 550 SP primers using 6.1 gr VV 3N37 under a 115 gr FMJ bullet. He supplied the powder and the bullets.
To provide a comparative reference I also loaded test rounds with the same primers using 4.9 gr Alliant Bullseye and the 115 FMJ bullets [listed as a maximum] and also included the CCI 400 SR primer and the CCI 450 SR magnum primers. Testing was done in a 10” Contender barrel with a strain gauge affixed and connected to the Oehler M43 PBL. The SAAMI MAP for the 9mm cartridge is 35,000 psi.
The test of the comparative reference load [4.9 gr Bullseye] proved quite interesting. The test results briefly;
Primer, velocity average, psi average:
CCI 500 SP primers; 1331 fps, 35,000
CCI 550 SP Magnum primers; 1341 fps, 35,000 psi
CCI 400 SR primers; 1338 fps, 35,000 psi
CCI 450 SR Magnum primers; 1330 fps, 35,000 psi
Note the test to test variation in velocity is well within the test to test expected variation of the same load. What was really surprising was the pressure for each and every shot, regardless of the primer, was exactly the same…..right at the SAAMI MAP for the 9mm cartridge. Looking at the internals [time/pressure curves, area under the curve and rise to pressure] a slight difference could be noted. The CCI 550 SP Magnum and the CCI 450 SR Magnum primers gave slightly more uniform internals than either the standard SP or SR primers!
I then conducted the second test using the provide VV 3N37 powder. The test results;
CCI 500 SP primers; 1236 fps, 32,300 psi
CCI 550 SP Magnum primers; 1253, 34,500 psi
Note, with the use of VV 3N37 powder, we have a distinct difference in results with this test than with the previous test with Bullseye. The internal ballistic measurements again indicated the CCI 550 primer gave slightly more uniform ballistics. The CCI 550 Magnum primer also gave a noted increase in velocity [20 fps increase vs the 10 fps difference with Bullseye] and an increase in pressure of 2,200 psi.
In a previous thread it was Lloyd Smale (If memory serves me correct as I couldn’t find the thread with “search”] that was adamant with is 9mm load of HS-6 in didn’t matter with his mid-level HS-6 load what primer was used as all were “safe”. He also rather adamantly suggested I test HS-6 and find out. So I did.
Lyman lists 6.2 gr HS-6 as their max load under a 120 gr 356402 bullet. I didn’t have the Lyman bullet but have the Lee 120 gr TC bullet [123 gr cast of COWW + 2% tin], so I chose to use that load. Even though Lyman lists that load as “max” the CUP measurement of 29,300 indicates it is not a “max” load as the CUP SAAMI MAP is 33,000. I have on hand 13 different SP and SR primers [7 SP primers and 6 SR primers] so I loaded up a test with each of them.
Again, the test load was 6.2 gr of Hodgdon HS-6 under the 123 gr Lee TC cast bullets.
The test results by primer used;
Small Pistol primers;
Federal 100 SP primer; 1255 fps, 34,800 psi
CCI 500 SP primer; 1227 fps, 34,700 psi
Magtech 1 ½ SP primer; 1243 fps, 35,000 psi
Winchester WSP SP primer; 1247 fps, 35,000 psi
CCI 550 SP Magnum primer; 1210 fps, 34,400 psi
Federal 200 SP Magnum primer; 1214 fps, 34,700 psi
Winchester WSPM SP Magnum primer; 1253 fps, 35,000 psi
Small Rifle primers;
Remington 7 ½ SR Primer; 1229 fps, 34,700 psi
Winchester WSR SR primer; 1220 fps, 34,800 psi
CCI 400 SR primer; 1237 fps, 34,800
Federal 200 SR primer; 1253 fps, 34,800 psi
CCI 450 SR Magnum primer; 1228 fps, 34,700 psi
Federal 205 SR Magnum primer; 1222 fps, 34,500 psi
Appears Lloyd was certainly correct, there really isn’t much difference regardless of the primer used. Also. interesting to note that 3 of the SP primers pushed the psi right to the SAAMI MAP whereas none of the SR primers did. That is one of the things I really like about this game and that is I’m always learning. In this case I’ve not only learned from actual testing but also through research to find the facts about primers. Turns out, once again, I and most others were misled over the years into thinking SP magnum primers and SR primers would increase the psi with a given load because they were “hotter” or had more explosive power. Turns out that isn’t true. The primers only hold so much compound and the energy produced by that amount of compound is finite. Thus, SP and SR primers essentially hold the same amount pf priming compound which essentially increases the same amount. SPM and SR/SRM primers apparently do not increase the psi per se by themselves. The difference is in the priming compounds and how they “burn”. The SPM and SR/SRM primers compound gives a longer flame burn is all.
So, if that is the case then why did two of the tests [the 357 Magnum with Unique and the 9mm with VV 3N37 powders] show a marked increase in psi with the SPM and/or the SR/SRM primers? The answer to that appears, at least so far, to lie in the nature of the powder used. My guess at this time is any real potential increase in pressure with the use of a SPM or SR/SRM primer will be dependent on what kind of powder is used [single or double based], the kind of deterrent [controls the burn rate] that is used and probably any flash retardant used. Thus, as it turns out, all who participated in the past thread were essentially correct some of the time and potentially wrong at other times. This is evidenced as I’ve not found any conclusive evidence one way or the other to definitively say substituting a SPM or SR/SRM primer in a 9mm load is safe because, like many things we’ve found in reloading, it depends.
I will still, as of this writing, stand by my original suggestion; if one has to substitute a SPM or SR/SRM primer in the 9mm cartridge for a load proven safe with a SP primer developed load then use caution.
or 
