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Discussion Starter #1
One of the guys in the Les Baer forum was having some ejection problems with a Stinger and also mentioned the firing pin strikes were off-center and displayed a "skid mark", where the firing pin dragged across the primer. He eventually sent the gun back to Baer to get fixed. It came back working perfectly and just as a side note, there were no more "skid marks" on the primers.

So my question is: what causes "skid marks" on primers from firing pins? Seems like the barrel is unlocking from the slide before the firing pin has retracted. What would effect the timing cycle to cause this?
 

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A broken/weak firing pin spring, or the wrong recoil spring for the load you are using.
 

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Originally posted by Gravity:

You're sick! I knew someone was gonna think it.....



[This message has been edited by shane45-1911 (edited 06-12-2001).]
 

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Originally posted by shane45-1911:
A broken/weak firing pin spring, or the wrong recoil spring for the load you are using.
Good.

add a bent firing pin, Baer uses a unique .066 firing pin hole. If the pin drags in the hole? Ti pins sometimes do it and with the Ca. testing some noted the use of ti pins for the drop test. If the firing pin stop hole is not centered side to side or up and down, burred or too close to the firing pin it may drag or slow it down.
geo ><>
 

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Was the FP actually dragging along the primer surface, or was the skid mark actually two FP dimples overlapping? My FP leaves a very faint second dimple that appears on the edge of the "crater" with light loads. With heavier loads, the second dimple is more centered in the first one.
 

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Discussion Starter #7
Thanks for the ideas guys!


feedramp, I'm not sure what the Baer owner was seeing exactly. I was just interested in what caused this sort of effect.
 

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This sure aint what I thought "skid marks' were all about.
 

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read it somewhere in the magazine, it said that this indicate the breech is beginning to open before the firing pin is fully retracted by its spring. it's not dangerous, but in time this could damage the tip of the firing pin or even break it off. they suggested to replace with a heavier recoil spring. hope this help.
VC
 

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If you understand what is happening, you can better find the cause.

In order for the FP to cause a "skid mark" on the primer surface, there must be some force applied to the FP for the duration of contact strong enough to cause the FP, a blunt, smooth, rounded surface to actually etch a mark in the primer metal.

The force applied by the hammer is more than strong enough to put it there, but, because the FP is the inertial type, its resting position places the tip of the FP behind the breech. The FP spring does this job, assisted by the rearward force of the case on the FP as it reacts through the headspace distance due to recoil.

Second, there must be some relative (radial) motion between the FP and the case, assuming the primer is not moving in its primer pocket, for this to happen. Since we are assuming that the FP is causing the marks, the etching must be happening either during detonation or shortly afterward, when the gun is reacting to recoil. It seems reasonable that this is the most opportune time for the etching to occur, since the gun is no longer in battery, and the case is no longer held firmly in the chamber.

This leads to the question, what is causing the radial motion to occur, and what component is moving, the FP, or the case, or both?

If the case is moving, then it must be that the FP is not retracting quickly enough to avoid the etching, if at all. The combination of the force of recoil and the FP spring are not enough to get the FP out of the way of the case as it travels on its way to the ejection port.

A cursory visual inspection of the postition of the extractor claw on the case shows that the claw is not always exactly at the 3 o'clock position on the case, and therefore is not pulling the case straight out of the breech. Thus, the extraction force on the case is not straight rearward, but has a radial force component. This can be considered normal.

If the above is true, then the trouble lies in the rearward motion of the FP, which is inhibited by one or more factors. Some possibilities include a broken spring, debris in the FP channel, or a very weak or shortened spring.

If the problem is not due to FP rearward motion, then the FP hole in the breechface could be elongated, allowing the FP to move in a radial direction in addition to its normal linear motion. Again, the force must be maintained on the FP for the duration of contact with the primer surface.

Another possibility is a very weak recoil spring, which would allow the gun to unlock and begin the extraction process before the FP can be forced clear of the primer surface. Although it doesn't seem likely that this alone could cause the marking, it could combine with other factors to produce the results observed.
 

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Discussion Starter #12
Whoa feedramp! Nice dialog of what could be doing that! Are you an engineer or something?

I originally asked this question because of a guy experiencing this on his Baer Stinger. I took a look at cases from my commander after last weekends IDPA match and noticed that my "hotter" loads caused a slight firing pin drag mark on the edge of the firing pin crater on the primer. It was in the upward direction meaning the barrel was beginning to unlock before the firing pin retractd. I've been running a 18 lb variable recoil spring in it. Going to try a 20 lb variable and see what happens. Another possibility is the firing pin spring being weak. I'll try one thing at a time and see what happens.

Thanks for all the suggestions!
 

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Joey,

You're talking about streak marks.

10ring,

You've got the right idea...try your fixes one at a time. If you use the shotgun approach, you may not know which one did the trick.

No, I'm not an engineer.
 

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I was just gonna say weak springs and a poor finish job...Guess not...LOL...

------------------
>>>>>>>>>>g2<<<<<<<<<<

I Like The Shade Too!
 

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After reading this post, I looked at my brass, and sure enough I'm experiencing the same phenomena as Feedramp described. It looks like a second smaller dimple next to the main crater.

The gun seems to function fine. Should I try replacing the FP spring, or does it matter?
 

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Originally posted by Tim C:
The gun seems to function fine. Should I try replacing the FP spring, or does it matter?
You could try replacing with an extra power FP spring. This, in combination with a new recoil spring, may help.
 
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