What is "primer drag" in handguns?

po18guy

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High primers in a revolver. Usually caused by very light loads that do not set the case back onto the primer. Upon firing, the primer is partially pushed out of the case by pressure - the same pressure which expands the case against the chamber walls. As that pressure drops (bullet exiting the barrel), the case then pulls free of the chamber walls, but is set back against the breech face by residual pressure which re-seats the spent primer. With a very light, i.e. target load, the case may not be pushed all the way back, so the primers may protrude from the case head and drag on the breech face or recoil shield.

In a semi-auto, it could be a high primer which drags on the bolt face, slowing or stopping feeding. But high primers in autoloaders are also known to cause slam fires on a partially open breech. Not a good thing.
 

Velzey

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It’s not just subcompacts. Full-size Glocks have been doing it for years. And allot of other brands. And it’s not all of them either, it’s hit or miss. Fp are in tolerance but on the long side, take .005-.010 off the tip and the drag disappears.
The firing pin return spring isn’t strong enough to fully force it backwards out of the way fast enough. This is a none issue, I’ve never seen a broken fp from dragging.
 

MrRob96

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Primer drag usually indicates the firearm is, in case of semi auto handguns, unlocking early as the firing pin is still outside of the firing pin channel as the barrel starts sliding down in the common Browning action guns.

I think this topic has become huge because of MACs video on the P365. I have to disagree with MAC that no other handgun shows primer drag other than the P365.

All of my 10mm handguns do this, it indicates high slide velocity due to the high recoil energy of the round in this case. Primer drag is one of those pressure signs that lets you know your slide is really hoofing it.

In the case of pocket guns, low slide mass increases slide velocity and may lead to primer drag. Another thing is striker fired guns don't have a hammer to create a mechanical opposition to the initial rearward travel of the slide. When a hammer is in play, that hammer acts like a lever to soak up some of that extra energy. This can change the timing of the unlocking and reduce primer drag.

Anyways this guy's video definitely shows what's happening, but I don't think this guy knows why. I think this guy was one of the geniuses hitting the P320 with a hammer while it was braced against a table. Inertia... Sometimes physics aren't understood.

Yeah, primer drag will likely fatigue your firing pin or striker after a lot of rounds, depending on primer material and how the firing pin is manufactured as well as other variables.

Welcome to pocket guns. It's not as simple as chopping down the barrel and grip.
 
another version is "high primer" caused by out of spec handloads where the primer is not properly seated all the way into the primer pocket:cool:don't ask how my research discovered this anomaly....
 

DirectDrive

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Another thing is striker fired guns don't have a hammer to create a mechanical opposition to the initial rearward travel of the slide. When a hammer is in play, that hammer acts like a lever to soak up some of that extra energy. This can change the timing of the unlocking and reduce primer drag.
This ^^^
Probably a lot of it right there.
 

po18guy

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The embedded vid in the OP did not show up, for some reason, when I responded. My answer was the traditional target revolver firing pin drag. But, advancing tech has a way of re-defining things for a new generation of pistols. It seems like "firing pin lag" or "Firing pin drag" is a more apt description, since the primer is essentially innocent if it is the pin's fault.
 
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po18guy

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Primer drag usually indicates the firearm is, in case of semi auto handguns, unlocking early as the firing pin is still outside of the firing pin channel as the barrel starts sliding down in the common Browning action guns.

I think this topic has become huge because of MACs video on the P365. I have to disagree with MAC that no other handgun shows primer drag other than the P365.
I just bought some once-fired factory load .41 AE brass and the primers showed evidence of this anomaly. And that probably happened 30 years ago. I know of no .41 AE Glocks, so it must have been some other firearm. It may be associated with the stamped/flat metal firing pins that leave their "Glock-like" narrow impression on the primer.
 

Velzey

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I had this happen years ago in a 1911 that I'd had since I was a teenager and had fired unknown thousands of rounds through. The problem vanished along with the severely worn and weak recoil spring that I replaced.

One weak firing pin spring is all it takes... it’s thats springs job to retract that fp just enough for smooth ejection.

Anyhow I sent James a message to get him on this problem. It seems to be spreading like wildfire on the interweeebs, mostly on social media. But who else to look into it but none other than Yeager...:eek::D

8858D0C8-8D14-4ED4-A229-B3E530468E1B.jpeg
 

MrRob96

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I'm sure James is on the case.

Maybe after the problem with the P320 where people were complaining of light strikes, Sig cranked up that striker spring weight and it's bubbleguming with the entire equation now.

What's the striker return mechanism on these guns? It seems like it's all the job of a single spring working in both compression and tension. Doesn't seem like a great system to work in a wide variety of applications easily.

Sig needs to get some real engineers on the job. The interns aren't cutting it.
 

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