Slam fires

[splicer]

I thought that maybe some of you guys could answer a question for me.I heard that typical civillian ammo has a softer primer than military.In an AR the firing pin would actually dent the primer,sometimes causing a round to go off.I bought a thousand 223 rounds just because they were in stock,PMC remington 45 grain HP.Just wondered if they would work in an AR.I dont have the rifle yet,Just wanted to be sure I could fire it safely.Ive also noticed that some AR rifles say 556 and some say 223.I understand the difference,I plan on a 556 so I could fire either with no problem.JUst wasnt sure about the slam fire thing.

[cjclemens]

You shouldnt have any trouble with .223 in an AR.  The main difference is that 5.56 military ammo usually runs at a slightly higher pressure.  My only concern would be that the 45gn HP's may not stabilize in an AR type rifle.  New AR's have 1:7 to 1:9 twist rifling which tend to prefer 60 gn or heavier bullets.  I use wolf ammo loaded with 62 gn bullets, and ive had great results.

As far as hard primers go, the military ammo uses them to reduce the chance of slamfires, which is generally only a concern in a heavily fouled rifle.  If keep your AR clean, you'll never have a problem with regular primers.

[jmayton]

The 5.56x45 is slightly different in dimensions from a .223.  Basically, you can fire a .223 in a 5.56 chamber with a potential loss in accuracy, but do not fire a 5.56 in a .223 chamber.  As for the slam fire issue, I will notice the occasional slight dent in my primers from the firing pin hitting them when the action closes, but I've yet to have a slam fire.  A different bolt and/or firing pin might cause one though.  In general, you're safe to shoot commercial .223 in most any AR you buy today. 

[cjclemens]

If you want to get really picky about it, the difference is not in the cartridge dimensions - it's the chamber dimensions.  Also, there's a significant difference in max pressure, so its not a good idea to shoot 5.56 in a .223 -not that it wont fit, but you'll have all kinds of misfires and stuck case problems.  However, .223 will perform just fine in an AR.  Accuracy will not suffer as long as you match the bullet weight to the rifling.  If you get dented primers or slam fires from your AR, its time to take the bolt assembly apart and clean it.

[Savage]

cjclemens,
Never saw an AR that didn't leave a small indentation in unfired primers on chambered rounds. (My bolts are clean & pristine----at the beginning of the match anyway!)
Savage

[splicer]

Thanks guys.I wasnt sure and just a little concerned.

[cjclemens]

Never saw an AR that didn't leave a small indentation in unfired primers on chambered rounds.

Mine doesn't.

[Savage]

Never saw an AR that didn't leave a small indentation in unfired primers on chambered rounds.

Mine doesn't.

Glad to hear that! Conservatively speaking, I've been on the line with scores, if not hundreds of ARs in addition to my own.  Any chambered, then unfired round I've checked after policing the range has had the firing pin dimple in it. Some are more pronounced than others, but all have been marked. That makes your AR the exception to the norm in my experience. If you know how to keep that free floating firing from striking the primer as the bolt slams forward, I'd like to know what it is. I don't like the dimpled primers either! Some go to the Titanium firing pins. It helps some, but there's still enough inertia to mark the primers. I should add that I have never had nor seen a slam fire in an AR, with commercial or reloaded ammo.
Savage

[cjclemens]

I havent done anything special to my AR.  It's more or less a bone-stock DPMS, and its never left a mark on unfired primers until I have quite a few rounds through it.  I use CCI primers in my handloads - perhaps theyre a little bit harder than winchesters and others.

[Default]

From mine and friends/family experiences all combined , It seems the SKS with civilian ammo is the most common culprit for slam fires ( that big heavy bolt)... Personally i havent been able to get any of my military arms to do so over countless rounds down range ... But then again after 5 SKS's and 2 AK ( 47/74) and a whole slew of various other military type weapons I can count on two hands how many commercial rounds i have fired through them...Well except for my DPMS AP4 LR 308 ... But even then i havent had that weapon slam fire either

 As for the AR you should be ok ... Not even using benchrest primers in 223/556 have i got it to slam fire ... Though experiences may vary on this.

     Hope this helps,

        Default

[jmayton]

cjclemens, thank for the correction on the difference between the 5.56 and the .223.  I have never noticed a significant accuracy loss shooting .223 in my 5.56 AR, but I've heard that it can occur.

I don't know everything about primer ignition, but I do know that velocity has something to do with it.  As a test to see how safe carrying a decocked Mosin-Nagant with a round in the chamber would be, I chambered a primered case and commenced to hit the back of the cocking piece with a rubber hammer.  Never went off.  I had a nicely dented primer (not as much as a fired round) but no ignition.  This is with the firing pin sitting on the primer, not a floating pin.  I still wouldn't carry it that way, but it shows how much velocity is required to ignite a primer.  I don't think an AR-15 bolt can create enough force and velocity to ignite the primer.  I guess it can happen, but it doesn't seem likely.

I've never had a slam fire in neither my AR nor my AK.  I haven't shot an SKS enough to know about it. 

[cjclemens]

I guess my AR is the exception, not the norm as far as denting primers.  When mine is clean it wont do it, but it starts to ding them a little as it gets fouled.  On the other hand, both my AK and SKS leave a pretty good dent on on the unfired round in the chamber.  Regardless, it still takes a pretty good whack to touch one off.  Most slam fires I've heard of were due to a firing pin that's actually bent and stuck in the forward position.

[S.S.]

I fire .223 rem marked cases and 5.56 marked cases in my Mini 14 with no problem what so ever.
Have for years. The only rifle I have ever had a problem with was an H&R handi rifle.
I believe that is because of how the handi actually extracts the case, straight back with no camming action at all. Have had extraction problems with it also in other calibers.
Also, I have never had dented primers in SKS Rifles that I remember ?

[Savage]

I've had a few SKSs. Still have one in the back of the safe somewhere. All I've ever fired in them was Wolf steel case. Never had a slam fire no matter how dirty they were. I don't remember seeing a firing pin mark on unfired primers. Of course I didn't eject many unfired rounds, and don't remember looking at them very closely.
Savage

[cjclemens]

The only rifle I have ever had a problem with was an H&R handi rifle.

If you're shooting 5.56 loads in a Handi, they'll stick more often than not.  Handi's in .223 have a fairly tight chamber.  With 5.56 loaded at higher pressure than .223, you'll have cases stick left and right.  I wouldn't expect to see a .223 blow up from a 5.56 load, but keep in mind that the pressure 5.56 runs at is about equivalent to a .223 rem proof load.

[mcwoodduck]

The only slam fires I have had was with an M1 Carbine and poorly reloaded ammo where the primer was not fully seated.  the case came apart and sprayed me with hot gas and burning powder.
I also had my M1 Garand go full Auto but that was the previous owner playing with the secondary sear to studder and allow the bolt to lock up.
If an AR goes into slam fire all you need to do is either clean the firing pin and the bolt of any goop that is holding the pin forward.
Or check your ammo.  You may have a high primer or two that will pinch and fire out of battery and cause all kinds of mayhem.