Primer setback on factory 12ga ?

KyleSchenk

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Anyone ever come across primer setback with factory loads before? Is this just a case of low pressure loads ( Score 2 3/4” 00 buckshot) or should I be looking at other factors here? There was only one empty that displayed this setback. The rest were normal.
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Slightly oversized primer pocket???
Could have been. I've never seen in set back let alone as far as this one in any of the factory ammo I've shot over the years 🤷‍♂️. The only reason I even noticed this one is because I was doing testing and had all the shells labeled to track my data. The rest of the 100 or so emptiea we're normal
 
You might want to get the headspace in that gun checked, if that was fired and came out of a locked up chamber like that? I doubt that primers can "set-back" once they are out of the chamber lock-up - but there it is. I have seen primers "fall out" when action opened - usually WAY too hot load that expanded the primer pocket so nothing to hold the fired primer in place. I've never seen that on a shotgun shell though - and I've never seen that with factory ammo, either.
 
I’d say it was just a faulty case with an oversized pocket. If it was that way before being fired the gun would either seat the primer when closing or prevent the gun from chambering the round. From the look of the primer I’d say no signs of high pressure. If there was more like it then I would have concerns about the firearm!!
 
Anyone ever come across primer setback with factory loads before?
What kind of action was it fired in? Manual action, did you pull back just slightly on the slide when it was fired?


Slightly oversized primer pocket???
Please explain how an oversized primer pocket could possibly allow the primer to back out when the action is locked up and the shell held firmly against the breech face?

What makes you think a normal sized primer pocket holds the primer in place against 11,000 psi?

It SHOCKS me the number of people posting on this forum who fundamentally do not understand how firearms work. :rolleyes:
 
I’d say it was just a faulty case with an oversized pocket. If it was that way before being fired the gun would either seat the primer when closing or prevent the gun from chambering the round. From the look of the primer I’d say no signs of high pressure. If there was more like it then I would have concerns about the firearm!!
Can you push the primer back in with thumb pressure?
If so it’s prob just a loose primer pocket
I have heard of this being a problem with score. Primes don’t usually set back on shotshell even when over pressure.
I think you guys have identified the problem. I was able to easily seat the primer back down with little thumb pressure. I cut the crimp section off the hull and can push the primer back and fourth about .02" between seated and sitting proud. It's the only shell out of all fired that day and now checked that exhibits this movement of the spent primer.
What kind of action was it fired in? Manual action, did you pull back just slightly on the slide when it was fired?



Please explain how an oversized primer pocket could possibly allow the primer to back out when the action is locked up and the shell held firmly against the breech face?

What makes you think a normal sized primer pocket holds the primer in place against 11,000 psi?

It SHOCKS me the number of people posting on this forum who fundamentally do not understand how firearms work. :rolleyes:
I'm thinking the pocket was oversized but primer was seated. After firing & ejection, the shell hit the concrete pad on the firing line at the right angle allowing inertia to easily drive the primer partially out of a loose pocket.

Thanks everyone for your insights. I really appreciate it. I'll check back in if I find anymore anomalies.
 
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I just mean there’s still burning and expansion happening once the bolt comes off the shell. So if a loose primer picket. Could push the primer out.

To many people think that has operated guns are just gas operated. The shell still helps push the bolt back. The gas portion is moreso to unlock the lugs
 
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