Testing CCI 400 primers for slam fire in an AR15

R

Roach711

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I finally ran out of my “lifetime” supply of Remington 7 ½ small rifle primers and couldn’t find any more locally so I got some CCI 400’s instead. I’d read that the 400’s aren’t as slam fire resistant as the 7 ½’s so I decided to see how easy it would be to get a slam fire in my AR. (Anderson upper and bolt, AR Stoner barrel with wylde chamber).

I primed an empty, trimmed, and full length sized LC12 case with one of the 400’s, dropped it into the chamber then pulled the bolt back to the stop and let it fly. The primer was slightly dimpled as expected but no bang. Using that same primed case I repeated the test 50 times in all and no slam fire. The primer dimpled on the first try and after 50 tries the dimple was a bit larger but nowhere close to looking like a fired primer.

Then I tried to get a slam fire with that same primer set slightly above the case base. I used my press to push the primer out a bit then cycled it through again. The result was that the bolt simply bashed the primer back flush into the primer pocket and no slam fire. I tried this 4 more times with the same result.

Next I set the primer out about a 16th of an inch and tried 5 more times to get it to go bang. All 5 times the bolt just set that primer flush.

Then it occurred to me that after 60 abusive chamberings the primer may have been damaged enough by my tender ministrations that it may not fire no matter what, so I flipped off the safety, pulled the trigger and got a satisfying Bang!

Those CCI 400 primers will do nicely!

If I get bored I’ll do the same tests on my loosey-goosey (allegedly) slam fire prone M1 Garand.
 
Slam fires in AR's are something to talk about if you drink coffee at gun shops but making sure never hurts...
 
I use CCI 450 primers in 223

http://www.accurateshooter.com/technical-articles/primers-and-pressure-analysis/

What does all this mean to the reloader?
- Cases that utilize small rifle primers and operate at moderate pressures (40,000 psi) can use CCI 400, Federal 200, Rem 6 1/2, or Win SR. Such cases include 22 CCM, 22 Hornet and the 218 Bee. Other cases that use the small rifle primer can use the above primers only if moderate loads are used. Keep to the lower end of reloading recommendations.

– Cases that utilize small rifle primers and operate at higher pressures (55,000 psi) should use CCI 450, CCI BR4, Fed 205 and Rem 7 1/2.

– All the large rifle primers measured have the same thickness. Therefore choose based on other factors, such as accuracy, low ES/SD, cost, cup hardness, and uniformity.
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That article is out of date as far as CCI# 400 . CCI has since reworked there 400 primer cup to be harder . I don't recall the date but want to say 10 or so years ago
 
hagar wrote:
Now try it with Winchester primers. I would bet money you will get a slamfire.
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1600+ rounds into my supply of Winchester Small Rifle primers in .223/5.56 and zero problems, so when you're deciding how much to bet, don't bet the farm.
 
Calling Unclenick :p

I just started loading for .223 (AR) this year. I bought a brick of CCI 400's at my LGS to get started. I have since loaded/shot a few hundred with no slam-fires.

In conversation with a buddy of mine (via text) a few months back, I mentioned the CCI 400's and he immediately responded with the alleged slam-fire phenomenon and recommended #41's.

I haven't done anything since that conversation (loaded or shot any ammo). And decided to get #41's moving forward. But what about the 600 or so CCI 400's I still have (loaded and loose)?

So this has been weighing on my mind a little - but not enough to start a post-thread.

But here we are now. I'd sure like to get Unclenick's take on this. Aside from him knowing a heck of a lot of all things gun, he seems to be particularly knowledgeable about primers. I'd really like to know if getting new primers is necessary.

P.S. If I ever chamber a round into any gun, I always always always make sure the firearm is pointed in a safe direction - but still.
 
Lubricated firing pins and a bit of crud from failing to keep the gun clean will give you slam fires more often than using a "soft" primer. The firing pin and its channel should be clean and dry. Never use lube of any kind on a firing pin.
 
Nick I've used CCi #400 exclusively for years and several thousand rounds through multiple AR's with no issue what's so ever .

Here is a photo of a load development I did using H-335 and 55gr FMJ-BT . These were shot using CCI#400 in LC cases

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The set of cases on the right had a charge of 26.5gr with a velocity of 3100+fps . As you can see no cratering , over flattening or pierced primers . The cup is plenty hard IMHO .

For comparison purposes here is the cases running duplicate charges with CCI#450 Pretty much the same even though the #450 are supposed to be harder .

dSCU4O.jpg

3wFybX.jpg


On a side note though I shot one of my hotter loads for AR in a 223 chambered rifle last weekend . These loads shoot fine with no pressure sings when used in an AR but had a good amount of cratering when fired from the 223 but no pierced primer , we did not shoot many because of the cratering . Bolt lift on the 223 was fine though but still did not want to push it .
 
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Then it occurred to me that after 60 abusive chamberings
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When things occur to me it always starts with 'and' like "And then etc. etc.".

When using the inertia bullet hammer puller I discourage reloaders from pulling bullets with high primers. What would be the difference? Powder can trickle down through the flash hole and fill the space between the anvil and bottom of the primer pocket.

Slam fire? Same thing. A shooter can get an assist with slam fires if the powder trickles through the flash hole and fills the space between the anvil and bottom of the primer pocket.

F. Guffey
 
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I have been using CCI primers in AR-15'S For over a decade now.
I have used tens of thousands of BR-4, 450's, and yes.. thousands of 400's

I use 450's when using ball powders because a bigger flash helps ignite ball powders more consistently.
I use BR-4 primers When using extruded powders in my accuracy minded varmint loads.

For plinkers I would have no problem using CCI 400 if I didn't use 450's for the ball powder ignition advantage.

I have seen exactly 1 slam fire in my life including hundreds of thousands of rounds on the range in the military, and as a civilian, and that was my brothers runaway SKS when a piece of copper got lodged such that the firing pin was stuck and protruding outward.

Slam fire? Same thing. A shooter can get an assist with slam fires if the powder trickles through the flash hole and fills the space between the anvil and bottom of the primer pocket.
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Guffey is making a great point here though, that essentially a slam fire won't really happen if there is room to simply seat a high primer deeper rather than ignite it. But if some ball powder fills the gap, and acts like a false barrier, the boom, potential slam fire.
 
Like most people posting, I have reloaded quite a few .223 rounds and fired them in an AR using whatever primer I happened to grab. And nothing unexpected happened.

However, I believe that it is possible to have a slam fire. Anyone who has ever chambered a round in an AR and then extracted it has seen the firing pin indentation.

The thing is, that I don't want to have a slam fire. So, I started using CCI #41 primers. It makes me feel better about the whole thing. In my mind, I realize, based on my own first hand experience that the likelyhood of having a slam fire is remote, but personally, I want to make the chance of it even more remote.

I am not someone who buys into a lot of drama and typically when I hear someone start talking about something being dangerous, I roll my eyes. But in this case, I don't see the downside to being careful. It's just a matter of using a different primer. I have to use some primer. I have to buy some primer. In this case, all I have to do is buy this primer instead of that primer and I feel better about the whole thing.
 
Not to put too fine a point on things, but if the firing pin was actually fitted to the bolt, you wouldn't get the dimpled primer...
That's one of my pet peeves with AR clones rifles, usually not very well fitted, and mixing AR-15 & M-16 parts creates issues.
 
Now try it with Winchester primers. I would bet money you will get a slamfire.
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How much money do I win? I have shot many, many thousands or rounds through AR's using Winchester SRP's and never had a single slam fire. Not with the old "white box" and nickel plated primers or the newer "blue box" natural color primers.
 
"...........if the firing pin was actually fitted to the bolt, you wouldn't get the dimpled primer..."

How does this work ?
What stops the firing pin from moving forward when the bolt closes ?
 
if the firing pin was actually fitted to the bolt, you wouldn't get the dimpled primer..."
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As 444 wants to know , I to would like you to elaborate on this . You said something about clones but if I recall the original M16 had to reduce the size/weight of it's firing pin do to this very issue and is likely where the harder cup primers are needed came from .

So how do you "fit" a "free floating" firing pin to where it can still "freely" move back and forth and not contact the primer ?
 
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