.223 / 5.56 Primers Question

I've read that you *should* use mil-spec primers like the CCI #41 for loading .223 / 5.56 rounds for AR pattern rifles due to the "floating" firing pin.

I have some of the CCI #41 primers, but I also picked up around 6000 CCI small rifle MAGNUM primers the other day and was wondering about using these in the AR rounds.

My thinking goes like this:

CCI primers are known for having thicker cups (a.k.a. being "harder").

These are also magnum primers which IIRC have thicker cups than standard primers to withstand the higher magnum pressures.

So I'm thinking these should be fine for loading the AR rounds. Especially if I dial the powder charge to absolute minimum before working up - to leave a little room for the potential for a slight pressure increase from using a "hotter" magnum primer.

Any thoughts on my reasoning, or the whole idea in general?

Use the CCI #41 primer. The CCI-550 small pistol magnum primer is allegedly the same as the CCI-400 small rifle primer. I've used many of these (thousands) without problem in ARs, but they are not recommended because of thinner cups and the possibility of a slam fire, even if it's a remote possibility. However, because the cups are thinner, they flatten noticeably in comparison with the #41 or CCI-450 small rifle magnum primer. With the flattening, there is a chance the thinner cups will pierce, particularly with a maximum load.

Your reasoning is fairly sound, but in the interest of safety, go with the #41s, CCI-450s, or Remington 7 1/2 for loading .223s for ARs.

primers

BC38 said:

I've read that you *should* use mil-spec primers like the CCI #41 for loading .223 / 5.56 rounds for AR pattern rifles due to the "floating" firing pin.

I have some of the CCI #41 primers, but I also picked up around 6000 CCI small pistol MAGNUM primers the other day and was wondering about using these in the AR rounds.

My thinking goes like this:

CCI primers are known for having thicker cups (a.k.a. being "harder").

These are also magnum primers which IIRC have thicker cups than standard primers to withstand the higher magnum pressures.

So I'm thinking these should be fine for loading the AR rounds. Especially if I dial the powder charge to absolute minimum before working up - to leave a little room for the potential for a slight pressure increase from using a "hotter" magnum primer.

Any thoughts on my reasoning, or the whole idea in general?

Click to expand...

I have done this very thing with many thousands of small pistol magnum primers....Praire Dogs in Montana just don't care ...neither do any of my rifles....my load is certainly NO hotrod, just runs the bolt back and forth reliably and is accurate.

You decide what's best for YOU!

Randy

According to CCI, what makes the #41 primer "different" is the increased space between anvil and primer.

Personally, I don't know anyone who's had a problem using any SRP in a .223/5.56 AR. But I stick to rifle primers for rifle ammo, pistol primers for handguns.

Small Pistol primers have a thinner cup than small rifle primers. And the small pistol primers are not designed for high pressure rifle rounds. Example it is recommended that the AR15 rifle use primers with a cup thickness of .025.

CHOOSING THE RIGHT PRIMER - A PRIMER ON PRIMERS
Primer Info & Chart + Milspec Primers for Semi-Autos & Other Primer Applications



Below a CCI 400 primer with a .020 cup thickness that was fired in a AR15 rifle. Bottom line, the thinner cups are designed for lower pressure cartridges like the .22 Hornet and .30 Carbine.



NOTE, when Remington ran Lake City Army Ammunition plant from 1941 till 1984 the Remington 7 1/2 primers were used in 5.56 ammunition. The CCI #41 primers were a solution for a problem that did not exist when ATK was awarded the contract at Lake City in 2004.

rockquarry said:

Use the CCI #41 primer. The CCI-550 small pistol magnum primer is allegedly the same as the CCI-400 small rifle primer. I've used many of these (thousands) without problem in ARs, but they are not recommended because of thinner cups and the possibility of a slam fire, even if it's a remote possibility. However, because the cups are thinner, they flatten noticeably in comparison with the #41 or CCI-450 small rifle magnum primer. With the flattening, there is a chance the thinner cups will pierce, particularly with a maximum load.

Your reasoning is fairly sound, but in the interest of safety, go with the #41s, CCI-450s, or Remington 7 1/2 for loading .223s for ARs.

Click to expand...

I'm sorry, I made a mis-statement in my original post.

The primers I actually have aren't CCI 550 small PISTOL magnum primers.

They are CCI 450 small RIFLE magnum primers. So, per the chart above they should be good to go.

I will correct the info in my original post. Sorry for creating confusion. Thanks for the quick answers.

I've used nothing but CCI Small Rifle Magnum primers in my AR ammo.

I've never had a slam fire.

It is all a bunch of nonsense.

How many MILLIONS or more rounds of 223/556 ammo have been loaded with standard SRP?? How much data is out there showing SRP??

Accurate powder which has 556 load data uses a Win SRP
and a SRP BR for 223 (which brings up another nifty Primer?

Hodgdon uses a SRR for 223 and doesn't bother with "service loads"

OH wait, Noster has 556 service loads using a yet again Win SRP.

#41 primers came about as a great marketing ploy, The were net around therefore not used before they where "advertised,

Slam fires are also pretty NON existent and it not an issue, perhaps maybe if one is just thousand of rounds of FULL auto,

But the Internet BS continues and is repeated,

Been using Winchester small rifle primers for years, never had a problem.

Usually, the reloading manual will recommend whether to use a standard or magnum primer; depending on powder used. I've always used Small Rifle Standard primers because that's what was recommended. Some powders do require a magnum primer for full ignition of powder. I think you'll be fine, good shooting.

Rule3 said:

It is all a bunch of nonsense.

How many MILLIONS or more rounds of 223/556 ammo have been loaded with standard SRP?? How much data is out there showing SRP??

Accurate powder which has 556 load data uses a Win SRP
and a SRP BR for 223 (which brings up another nifty Primer?

Hodgdon uses a SRR for 223 and doesn't bother with "service loads"

OH wait, Noster has 556 service loads using a yet again Win SRP.

#41 primers came about as a great marketing ploy, The were net around therefore not used before they where "advertised,

Slam fires are also pretty NON existent and it not an issue, perhaps maybe if one is just thousand of rounds of FULL auto,

But the Internet BS continues and is repeated,

Click to expand...

I just couldn't agree with this more. We're in an internet urban myth loop.

All I use is SRP for .223/5.56. An M1 carbine uses a floating firing pin also. There is an internet myth going around about that one also. I have a few 450's around but I bought them by mistake. I might get them used up before I die but I doubt it.

I almost put the following story in my previous reply......

I've had two instances in my AR where I had a failure to fire ("click-no-bang"). In both instances, when those rounds were re-chambered, they fired normally.

I'm convinced on those two cartridges I hadn't seated the primer fully into the primer cup, and the first firing pin fall pushed the primer fully into the primer cup. Clearly:
1. A high primer didn't result in a slam fire. In fact, even an intentional and full firing pin fall didn't result in a fire.
2. Fully seated primers (primer seated slightly below flush) hasn't resulted in a slam fire.

Maybe other ARs enable farther firing pin float than mine does. (I'm shooting an S&W M&P Sport I.) But at least for me not only have I not have a slam fire, I've had a couple of instances where my mistake "encouraged" it and it didn't happen.

By far, I'm no primer expert, but a couple thoughts; I read (hopefully not internet wisdom) that small pistol magnum primers' cups are the same as small rifle primers. My "research/experimenting" had leaned that way too (used small pistol magnum primers in my single shot 223 rifle, no pierced primers). I have used standard large rifle primers in my Garand, even though I have seen the same "slam fire" warnings and I have never experienced a slam fire using CCI, Winchester, Remington and Wolf standard large rifle primers...

In the book below the testing and development of the M16 rifle is covered. Remington was running Lake City and the first 5.56 ammunition made had the Remington 6 1/2 primers with a .020 cup thickness. And there were slam fire problems and punctured primers so the firing pin was lightened and the Remington 7 1/2 primer was used with a .025 cup thickness.

Standard pistol primers have a cup thickness of .017 and some magnum primers have a cup thickness of .020.

Primers with a cup thickness of .020 are not recomended for high pressure rifle cartridges. Meaning they are for the lower pressure .22 Hornet and 30 Carbine cartridges. And you do not load the .357 Magnum to 55,000 psi.



Below, you are not to use primers with a cup thickness of .020 in higher pressure rifle cartridges. And it is recomended to use primers with a cup thickness of .025 in the AR15 rifles.

Can primers be used interchangeably?
Help Center | Remington

"In rifle cartridges, the 6-1/2 small rifle primer should not be used in the 17 Remington, 222 Remington, 204 Ruger or the 223 Remington. The 7-1/2 BR is the proper small rifle primer for these rounds."



Below the specifications for the military 5.56 case and #41 primer. The case is made of harder brass than commercial .223 cases and the primers have a shorter anvil. BUT the #41 primer was not adopted for the 5.56 until after 2001 at Lake City by ATK. Meaning a $hitload of 5.56 ammunition was loaded with Remington 7 1/2 before the primer spec was changed.