CCI No. 34 primers and 338 Winchester Magnum

460harry · Sep 15, 2021

I know CCI advertises these things as being magnum grade, equivalent to their 250 primers in charge. Normally I would get the usual large rifle magnum primer but the ongoing ammo crisis being what it is I had to settle for the 34s.

I shoot 300 Win mag and 338 Win mag. I expect to get no different experience with the 300 than a typical CCI 250 primer but does anyone have experience using 34s in 338 Winchester magnum or any non-7.62mm large rifle magnum caliber? The 7.62mm designation on the box makes me a little anxious.

Nevada Ed · Sep 15, 2021

CCI 7.62mm NATO-Spec Military Primers are a military large rifle primer containing magnum priming mix. The CCI #34 primers are a great choice for reloaders that use military cartridges. These primers are specially made to be harder to ignite which prevents slam fires in military type rifles with a floating firing pin.

Not needed if you are shooting a bolt action......

and they may be higher in price due to company marketing ploys and advertisement.

LAH · Sep 15, 2021

I shoot a bunch of these with 4895 powder in my 30-06. I can't answer your question but can say I have a nice Winchester M-70 that won't fire them 100%. Like Ed said, they use a harder cup.

rockquarry · Sep 15, 2021

I'd use them, but as a precaution would back off my regular load a grain or two and work back up. I doubt you'll see any difference in velocity, accuracy, or point of impact.

SMSgt · Sep 15, 2021

Per CCI, what makes their primers slam resistant is they use a slightly shorter anvil, not any particular primer mix nor cup hardness. Thus they may be more susceptible to misfire with a less-then-solid firing pin strike--a gun issue, not a primer issue.

DWalt · Sep 15, 2021

The #34 primer is less impact sensitive, to resist slam firing in M1 and M14 military rifles. There are different stories as to how it is made less impact sensitive, including a thicker cup, a shorter anvil, and a less sensitive primer mix, but I personally don't know how it is done. In any event, there is really no significant difference in primer performance between a standard LR primer and the #34. I have tested standard CCI LR primers against #34 primers in a .30-'06, and there is no detectible difference in average MV. I do use #34 primer in loading for my M1, even though I have never had a slam fire incident using regular primers in it.

BTW, I once did a fairly extensive test of CCI Standard LR primers against CCI Magnum LR primers in a .270 using IMR 4350 and both 130 and 150 grain bullets. Some loading manuals recommend using Magnum primers in the .270 with slow propellants, but my tests showed there was very little difference in average MV (with standard primers producing a slightly higher MV), and in fact I found the Standard Deviation of the MV was much lower when using standard primers. Maybe somewhere in the arctic, Magnum primers may be better, but I have to call BS on the loading manual recommendation to use magnum primers in the .270.

Nevada Ed · Sep 15, 2021

DWalt said:
The #34 primer is less impact sensitive, to resist slam firing in M1 and M14 military rifles. There are different stories as to how it is made less impact sensitive, including a thicker cup, a shorter anvil, and a less sensitive primer mix, but I personally don't know how it is done. In any event, there is really no significant difference in primer performance between a standard LR primer and the #34. I have tested standard CCI LR primers against #34 primers in a .30-'06, and there is no detectible difference in average MV. I do use #34 primer in loading for my M1, even though I have never had a slam fire incident using regular primers in it.

BTW, I once did a fairly extensive test of CCI Standard LR primers against CCI Magnum LR primers in a .270 using IMR 4350 and both 130 and 150 grain bullets. Some loading manuals recommend using Magnum primers in the .270 with slow propellants, but my tests showed there was very little difference in average MV (with standard primers producing a slightly higher MV), and in fact I found the Standard Deviation of the MV was much lower when using standard primers. Maybe somewhere in the arctic, Magnum primers may be better, but I have to call BS on the loading manual recommendation to use magnum primers in the .270.

Back in the late 60's. when we hunted Mule deer in the snow in Nevada, I had two miss fires using a cci std primer and missed a B&C rack, in 36* temperatures.

With my 270 and IMR4350 powder, I now only use a cci Magnum primer for my deer loads, for "Cold" ammo.

LAH · Sep 15, 2021

SMSgt said:
Per CCI, what makes their primers slam resistant is they use a slightly shorter anvil, not any particular primer mix nor cup hardness. Thus they may be more susceptible to misfire with a less-then-solid firing pin strike--a gun issue, not a primer issue.

Wasn't aware of that, thanks.

460harry · Sep 20, 2021

so the 34s came in today. I tried one with a 460s&w load. Typically I use 42.5 grains of H110 with a large magnum rifle primer behind a 300 grain bullet. To be cautious, I backed off to 40 grains of H110 even for the CCI 34. Good thing I did. The recoil, shockwave, and fireball were at least as big with the 34 primer and 40 grains of H110 as with the large magnum rifle primer and 42.5 grains.

I think the 34s are hotter than even the large rifle magnum primers.

Ivan the Butcher · Sep 20, 2021

I load 300 Win Mag, 264 Win Mag, 338 Lapua Mag, 458 Win Mag and 450 3 1/4" NE with the Federal 215 primer (large rifle mag). I prefer the M for match, but Lapua ammo company doesn't use the match primers. The 215 is the "Hottest" small arms primer in the world. That isn't the answer you ask for, but it is the primer you should be using!

Ivan

CCI No. 34 primers and 338 Winchester Magnum

460harry

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Nevada Ed

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LAH

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rockquarry

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SMSgt

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DWalt

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Nevada Ed

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LAH

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460harry

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Ivan the Butcher

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