CCI 350 Magnum primer [Archive] - Glock Talk


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11-10-2012, 18:34
From what I can gather in bits and pieces between threads, magnum primers kick up bullet speed 50-100fps. It ignites the powder mass near concurrent manner vs regular CCI 300 primer.

I need to know if magnum primers RAISES pressure inside barrel. Does it? How significant?

Specific case: 180gr XTP or Nosler, new cases, 9.30 +/- .05 gr of LongShot, 6" KKM barrel. Expecting near 1,400fps...

If you could spend a few minutes on your experience with Magnum 350 vs regular 300 CCI primer, please do.

Thanks in advance!

Pressure is a direct function of powder mass. But isn't the 350 really accelerate burn rate? Once the bullet is some distance down the barrel, pressure is really independent of primer type? Because powder mass is the same?

11-10-2012, 20:30
ModGlock17, I do use the 350 primers to help with more uniform ignitions, the extra pressure is only at the point of peak pressure inside the cartrdidge, which will be slightly higher it will add to the overall pressure curve as well even into the barrel.

I have gone to 9.4 grains of LongShot under the 200 XTP's which copied SwampFox's 1240 fps loading...One thing I have seen is the shorter 180 grain bullets only gain a few extra fps. However your 6" barrel is likely to see about 1325-1350 fps with that loading. ONLY testing will so for sure.

11-10-2012, 21:22
Thanks, Shadow!

Based on what you're saying, I'm no where near Living Dangerously at the edge, using 9.3gr LS for a 180 gr with CCI 350.

Some people threw out a couple of numbers that caused me to think twice about that load. They said Magnum raises pressure about 5k PSI. Second, they said the pressure built up is roughly +10%. May be I should also load a few at 9.0gr and 8.7gr.

Logically, regardless of which primer used, the powder amount remains the same at 9.3gr (on any grain) which only give so many gaseous molecules for expansion, I think. Igniting them more thoroughly in a shorter period of time should only cause the volume of gas to expand more quickly, but not more in volume (therefore pressure).

So I don't see the logic of their argument and need to check with you guys.

Best Regards.

11-11-2012, 09:06
You are in the performance range with your loading, I would watch for timing issues while using the longer barrel, you may see smiles on casings develop if the unlock occurs too soon. By that I mean, if you see a "smile" that exceeds the exposed area in the chamber where the cartridge sit normally. I don't think you will see any smiles at that loading in you 6" if the cartridge has good support.

A disection of Underwood ammo was done and posted over at 10mm Firearms site

He is using IMR800X in his loadings, now sure what primers he is running. But I work up my loads with magnum primers first to find out where I'm at then make change to standard primer look for differences in performance.

Best Regards!

11-11-2012, 09:37
I just switched to Winchester WLP primers for every 10mm load. In between a standard and mag primer strength wise, and will not cause extra pressure spikes that a dedicated mag primer will. In the small 10mm case it will reliably ignite any slow powder you throw at it.

11-11-2012, 10:04
Igniting them more thoroughly in a shorter period of time should only cause the volume of gas to expand more quickly, but not more in volume (therefore pressure)

Yes, but the inertia of the bullet is constant and therefore i think the dwell time is fairly constant too, if you light off more of those powder grains in the same amount of time i think the pressure will go up.

I'm no where near Living Dangerously at the edge, using 9.3gr LS for a 180 gr with CCI 350.
I would say that is true.
Personally, Id go back down to 9.2grs, that seems to be the magic number with the 180gr jacketed slugs for some reason, and do an accuracy test between the 300's and 350's. Id bet the 300's will work better

11-11-2012, 15:09
Thanks for your comments.

I've got some quickie data for using LS on 180gr with CCI 350 (1.255"-1.259"), on 6" KKM G20.

8.7gr just 3 shots: ave. 1312fps (1304-1325fps)

9.0gr just 3 shots: ave 1349fps (1343-1360fps)

9.3gr on 9 shots: ave 1355fps (1343-1379fps) [Shadow correctly est. this one)

On regular CCI 300, I had found that improvement in speed leveling out at 9.3 gr, that is my reason for 9.3gr at the start.

It seems that Mag primer helped to reach the leveling off a bit earlier, at 9.0gr or so.

Inspection of cases: they all appear the same. No visible deformation, except for primers seem to start flatten out (say 20% rather than totally flatten), even at 8.7gr of LShot. My 8.7gr LS with regular CCI 300 still have rounded primers.

11-11-2012, 16:54
ModGlock17, Thanks for the report! I don't care who you are those are great numbers from the 10mm, very respectible.
About the primers, yes they do start to show some flattening at these levels.