When I rack a round on my ar I get a very small primer dimple. My buddy is an m4 armorer and said it shouldn't do this but its done it since I got it brand new. The bolt is made by rra.
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light primer strike on round racking
- Thread starter beachhair234
- Start date
Re: light primer strike on round racking
Any pics of a primer with the dent in it? Like Redmanss pointed out the AR has a floating firing pin which means there is no spring to keep the firing pin from moving forward with the inertia of closing the bolt and leaving a slight indent on the primer. It is normal, but I would like to see if you have an abnormally deep indent just to be safe.
FYI, this phenomenon is why some reloaders like to use primers with harder anvils for use in ARs as soft primers have the slight chance of possibly being slam fired.
Any pics of a primer with the dent in it? Like Redmanss pointed out the AR has a floating firing pin which means there is no spring to keep the firing pin from moving forward with the inertia of closing the bolt and leaving a slight indent on the primer. It is normal, but I would like to see if you have an abnormally deep indent just to be safe.
FYI, this phenomenon is why some reloaders like to use primers with harder anvils for use in ARs as soft primers have the slight chance of possibly being slam fired.
Re: light primer strike on round racking
In the case of rifles like the AR-15/AR-10, etc....they all have free floating firing pins. Because of this, the inertia of the firing pin carries it forward slightly when a round is chambered and it strikes the primer as the bolt closes. This almost always results in a small dimple in the primer. Most of the time, it is NOTHING to worry about unless the dimple is getting deep into the primer (if you have any pics of the round in question or other rounds you have chambered but not fired, it might help). If you are using commercial 223/5.56 ammo, they usually have somewhat softer/thinner primer cups than military ammo and the dimple way appear worse than with mil surplus ammo.
If the dimple is getting deep into the primer, you could have an out-of-spec firing pin or their could be some debris in the firing pin channel causing the pin to protrude more than it should.
The rule of thumb is that you shouldn't rechamber an unfired round more than 3x as each time increases the likelihood of a slamfire due to repeated dimples on the round's primer. If you chamber and clear your rifle on a regular basis, make sure you change out the top round so that you don't rechamber the same round more than a few times.
This also reinforces the premise that you should always keep your rifle pointed in a safe/clear direction when chambering a round.
In the case of rifles like the AR-15/AR-10, etc....they all have free floating firing pins. Because of this, the inertia of the firing pin carries it forward slightly when a round is chambered and it strikes the primer as the bolt closes. This almost always results in a small dimple in the primer. Most of the time, it is NOTHING to worry about unless the dimple is getting deep into the primer (if you have any pics of the round in question or other rounds you have chambered but not fired, it might help). If you are using commercial 223/5.56 ammo, they usually have somewhat softer/thinner primer cups than military ammo and the dimple way appear worse than with mil surplus ammo.
If the dimple is getting deep into the primer, you could have an out-of-spec firing pin or their could be some debris in the firing pin channel causing the pin to protrude more than it should.
The rule of thumb is that you shouldn't rechamber an unfired round more than 3x as each time increases the likelihood of a slamfire due to repeated dimples on the round's primer. If you chamber and clear your rifle on a regular basis, make sure you change out the top round so that you don't rechamber the same round more than a few times.
This also reinforces the premise that you should always keep your rifle pointed in a safe/clear direction when chambering a round.
Re: light primer strike on round racking
DocGKR posted the following over on M4C (thread available here: http://m4carbine.net/showthread.php?t=19881)
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">A large SWAT team in this area had a failure to fire from an M4 with Hornady TAP ammo during an entry--fortunately no officers were hurt and the suspect immediately threw down his weapon when the carbine went click instead of bang. After the incident was concluded, the team went to the range and expended the rest of their carbine ammo and had one additional failure to fire. This same team had 3 Hornady TAP rounds fail to fire in training a couple of years ago. When Pat Rogers was teaching a class at a nearby agency, there were 5 failures to fire using Hornady TAP ammo. In all 10 cases, there appeared to be good primer strikes, but no rounds fired. On analysis, the ammunition had powder and checked out otherwise.
However, despite what appeared to be good primer strikes, two problems were discovered. First, when accurately measured, some of the primer strikes had insufficient firing pin indentations. The failed round from the potential OIS incident had a primer strike of only .013"—the minimum firing pin indent for ignition is .017". In addition, the primers on the other rounds were discovered to have been damaged from repeated chambering. When the same cartridge is repeatedly chambered in the AR15, the floating firing pin lightly taps the primer; with repeated taps, the primer compound gets crushed, resulting in inadequate ignition characteristics--despite what appears to be a normal firing pin impression. Once a round has been chambered, DO NOT RE-CHAMBER IT for duty use. Do NOT re-chamber it again, except for training. This is CRITICAL!!!
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DocGKR posted the following over on M4C (thread available here: http://m4carbine.net/showthread.php?t=19881)
<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">A large SWAT team in this area had a failure to fire from an M4 with Hornady TAP ammo during an entry--fortunately no officers were hurt and the suspect immediately threw down his weapon when the carbine went click instead of bang. After the incident was concluded, the team went to the range and expended the rest of their carbine ammo and had one additional failure to fire. This same team had 3 Hornady TAP rounds fail to fire in training a couple of years ago. When Pat Rogers was teaching a class at a nearby agency, there were 5 failures to fire using Hornady TAP ammo. In all 10 cases, there appeared to be good primer strikes, but no rounds fired. On analysis, the ammunition had powder and checked out otherwise.
However, despite what appeared to be good primer strikes, two problems were discovered. First, when accurately measured, some of the primer strikes had insufficient firing pin indentations. The failed round from the potential OIS incident had a primer strike of only .013"—the minimum firing pin indent for ignition is .017". In addition, the primers on the other rounds were discovered to have been damaged from repeated chambering. When the same cartridge is repeatedly chambered in the AR15, the floating firing pin lightly taps the primer; with repeated taps, the primer compound gets crushed, resulting in inadequate ignition characteristics--despite what appears to be a normal firing pin impression. Once a round has been chambered, DO NOT RE-CHAMBER IT for duty use. Do NOT re-chamber it again, except for training. This is CRITICAL!!!
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Re: light primer strike on round racking
If it's a tiny little mark that you can only really make out in bright light then it's fine. If it's a fairly noticeable dent it could be an out-of-spec firing pin.
If you're worried post up a picture but I bet it is normal.
If it's a tiny little mark that you can only really make out in bright light then it's fine. If it's a fairly noticeable dent it could be an out-of-spec firing pin.
If you're worried post up a picture but I bet it is normal.
Re: light primer strike on round racking
Its normal dude. Its due to the free floating firing pin as someone else mentioned. Make sure you rotate your rounds and not keep racking the same one over and over again. But if it looks like the dent might be too deep and the firing pin might be out of spec get it checked out by someone other than your buddy. He should've known that the M4/M16/AR's make a dent on the round everytime a round is racked. Hope this helps.
Its normal dude. Its due to the free floating firing pin as someone else mentioned. Make sure you rotate your rounds and not keep racking the same one over and over again. But if it looks like the dent might be too deep and the firing pin might be out of spec get it checked out by someone other than your buddy. He should've known that the M4/M16/AR's make a dent on the round everytime a round is racked. Hope this helps.
Re: light primer strike on round racking
I have seen a few slam fires during Highpower comps. Alot of guys switch out the stainless pin with one made of titanium. Myself included. They don't cost much and its a cheap insurance policy.
The reason for alot of slam fires in highpower is because of single round loading. You slide the round into the chamber and then let the bolt slam home on it. The bolt carrier has no resistance at all since it isn't picking up a round from the magazine.
If you aren't single round loading I agree with the other posters.....don't worry about it.
I have seen a few slam fires during Highpower comps. Alot of guys switch out the stainless pin with one made of titanium. Myself included. They don't cost much and its a cheap insurance policy.
The reason for alot of slam fires in highpower is because of single round loading. You slide the round into the chamber and then let the bolt slam home on it. The bolt carrier has no resistance at all since it isn't picking up a round from the magazine.
If you aren't single round loading I agree with the other posters.....don't worry about it.
Re: light primer strike on round racking
Thanks for the info. This makes me feel much better. Well, sorta. The ammo in question is Hornady TAP ammo. Unfortunately, I don't have any photos of the ammo as I'm away from that particular rifle for a while. I'll be sure to post them up once I get the chance.
Thanks for the info. This makes me feel much better. Well, sorta. The ammo in question is Hornady TAP ammo. Unfortunately, I don't have any photos of the ammo as I'm away from that particular rifle for a while. I'll be sure to post them up once I get the chance.
Re: light primer strike on round racking
I'm sure your okay. The light primer strike <span style="text-decoration: underline">IS NORMAL</span> in AR's. I dont think I ever had a round that didnt have one from going condition one on patrols. Just as I mentioned before make sure you rotate your rounds and point your weapon in a safe direction when rackin that round.
I'm sure your okay. The light primer strike <span style="text-decoration: underline">IS NORMAL</span> in AR's. I dont think I ever had a round that didnt have one from going condition one on patrols. Just as I mentioned before make sure you rotate your rounds and point your weapon in a safe direction when rackin that round.
Re: light primer strike on round racking
If you hand load make sure your primer seating depth is correct otherwise you increase your chances of a slam fire. I also use CCI # 41 primers which are mil spec and have a harder anvil than regular primers. I have seen quite a few slam fires in M1's M14's/M1A's and AR 15's over the years
If you hand load make sure your primer seating depth is correct otherwise you increase your chances of a slam fire. I also use CCI # 41 primers which are mil spec and have a harder anvil than regular primers. I have seen quite a few slam fires in M1's M14's/M1A's and AR 15's over the years
Re: light primer strike on round racking
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Casey Simpson</div><div class="ubbcode-body">Be suspect of anything else that armorer says. </div></div>
If you take nothing else away from this thread...THAT would be the thing to remember!
With all due respect to you and your buddy...if he is honestly a trained/certified armorer for the M16/M4/AR, it might be time for a refresher course.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Casey Simpson</div><div class="ubbcode-body">Be suspect of anything else that armorer says. </div></div>
If you take nothing else away from this thread...THAT would be the thing to remember!
With all due respect to you and your buddy...if he is honestly a trained/certified armorer for the M16/M4/AR, it might be time for a refresher course.
Re: light primer strike on round racking
Normal. Harder primers can serve as an extra safety measure against potential slam-fires with floating firing pins.
Normal. Harder primers can serve as an extra safety measure against potential slam-fires with floating firing pins.
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