Locked breach semi-auto Firing pin drag

[totaldla]

I have a KelTec P15 that is shaving primers.

Each primer strike shows firing pin drag - I'll attach a picture at the end.

The firing pin is round, the slide hole is round.

The shaving is to the side of pin strike, so it doesn't appear to be primer flowing into the firing pin hole.

In my mind, the dragging & shaving is happening when the slide/barrel unlocks a bit early.

A further clue is that I get a fair amount of crud in my magazines - more than I'm used to seeing with other pistols running this ammo. "Fair amount" means that I have to disassemble and clean the magazines every 300 rounds or I'll get malfunctions. No bulged brass.

Original recoil spring assembly - 600 rounds on it. It is a double spring captive affair.

The primer shaving gunks up the firing pin channel and eventually causes light primer strikes. The P15 is a pain in the butt to disassemble/reassemble.

I'm hoping someone can impart some wisdom on locked-breach designs that will help me understand the primer drag & shaving - hopefully something simple.

[tangolima]

It is a striker fire design. Can't find its schematic to be sure. Most striker fire doesn't extract firing pin tip during ejection, hence the "drag". It is actually not drag. Rather it is probably a "prying" impression the pin tip makes in the spent primer when the brass angles under the kicking force of the ejector.

If that's the case, there may not be much you can do. You can measure the firing pin protrusion to see whether it is excessive. If it is, you can choose to reduce it.

-TL

Sent from my SM-N960U using Tapatalk

[totaldla]

Originally Posted by tangolima

It is a striker fire design. Can't find its schematic to be sure. Most striker fire doesn't extract firing pin tip during ejection, hence the "drag". It is actually not drag. Rather it is probably a "prying" impression the pin tip makes in the spent primer when the brass angles under the kicking force of the ejector.

If that's the case, there may not be much you can do. You can measure the firing pin protrusion to see whether it is excessive. If it is, you can choose to reduce it.

-TL

Sent from my SM-N960U using Tapatalk

Whoa - I never thought of that! I was wondering why this pistol tosses brass over my head - makes sense. The firing pin may have more influence over spent case direction than the ejector/extractor.

I just realized that I can examine firing pin/slide motion by using my CCC* bore scope. I'll take a look at it. You're right, there may not be anything I can do about it
Thanks for the input.

(*)Cheap China C___

[totaldla]

Deleted

[44 AMP]

This is exactly the kind of mark on the primer I see when fired from my SIG P220s and I have seen it on primers fired in a P226, your picture shows the mark a bit "sharper edged" than what mine do, but its the same kind of thing.

The mark is not "on the side" of the firing pin strike, its actually on the top, when formed, and it is because the firing pin is not fully withdrawn when the barrel tilts down. SO, yes, this creates a "drag mark" on the primer, unlike other designs such as the Colt where the pin hits the primer and rebounds away from it before the barrel tilts.

In my guns, this causes no (zero) issues, or any build up of anything. It is difficult to tell from the picture, is there actually metal being cut/gouged from the primer, or is it just a shadow in the pic??

In my guns, no metal is cut or sheared, its just a dimple of displaced metal leaving the firing pin strike a bit "teardrop" shaped.

IF this is actually causing issues in your gun, I'd say its time for a smith to check it out, or the factory, if still under warranty.

[Doug Lee]

Interesting design, simple but effective.
Thanks,
Doug Lee
*

[totaldla]

Originally Posted by 44 AMP

This is exactly the kind of mark on the primer I see when fired from my SIG P220s and I have seen it on primers fired in a P226, your picture shows the mark a bit "sharper edged" than what mine do, but its the same kind of thing.

The mark is not "on the side" of the firing pin strike, its actually on the top, when formed, and it is because the firing pin is not fully withdrawn when the barrel tilts down. SO, yes, this creates a "drag mark" on the primer, unlike other designs such as the Colt where the pin hits the primer and rebounds away from it before the barrel tilts.

In my guns, this causes no (zero) issues, or any build up of anything. It is difficult to tell from the picture, is there actually metal being cut/gouged from the primer, or is it just a shadow in the pic??

In my guns, no metal is cut or sheared, its just a dimple of displaced metal leaving the firing pin strike a bit "teardrop" shaped.

IF this is actually causing issues in your gun, I'd say its time for a smith to check it out, or the factory, if still under warranty.

The photographer struggled to get enough contrast to show the scraping and the indent clearly . Yes, there is brass shaved off the primer that gets drawn into the firing pin hole when the firing pin withdraws.

I feel better now that Tangolima and you have helped me understand the mechanism. I'll probably give KelTec service a call and find out if they have reshaped the firing pin tip - usually they'll just send me parts so that I don't have to ship the pistol. I've gotten pretty good at disassembling that rear cover and replacing springs.

[totaldla]

I went back and played with locking and unlocking the slide while shinning a light down the gap. The firing pin clearly rebounds. So I think I know what is really happening.

A striker-fired design, the P15 extends the firing pin when the trigger is pulled, and the firing pin retracts (little spring inside the big spring) as soon as the forces holding the pin out are overcome by the rebound spring. All in all a pretty clever design - pretty much the same as Glock and M&P.

But..

A soft primer, e.g. CCI500, can trap the firing pin stopping it from rebounding. The downward motion of the barrel unlocking drags the firing pin against the primer. This creates a teardrop primer indent and digs a bit of brass that is sucked into the striker channel when the firing pin retracts.

I'm pretty sure that Keltec design fix is to increase the tip radius of the firing pin. And/or increase the power of the little rebound spring.

I'm half tempted to load up some cartridges using CCI450 primers as they have a thicker cup. And I have some CCI Blazer brass cased factory ammo I can try for giggles.

Thanks for the input as I thrashed trying to really understand the issue!

[44 AMP]

My Brownings (Sig P220s) are .45ACP, so they get CCI 200 LP primers, and I've never had any issues with them.

[totaldla]

I wish I could go back and edit my last post, oh well

I figured out the firing pin drag. It is the cut of the barrel foot - a touch shorter and more clearance than optimal. It is made more pronounced because the recoil spring is anchored to the frame instead of the barrel. The barrel can drop a bit with .020" rearward slide movement - just enough to drag across the firing pin.