P64 Trigger Guard Plunger Wear

[Randall_G]

Back in 2019, the trigger guard came loose while firing only the 60th round through the new-to-me 1970 P64. I did not recover the trigger guard pin, but presumed it snapped. Though, when I installed the new pin, I was surprised by how worn the plunger was. See image 4305. Fortunately, I purchased a new plunger and spring along with the pin.

While shooting my 1971 P64 this morning, the second round in the magazine failed to feed. First time the pistol ever malfunctioned. Cleared the malfunction and reloaded the magazine. Once again, the second round didn't feed.

Pulled the slide off and verified I hadn't installed the recoil spring backwards the last time I cleaned the pistol. Checked the magazine for obvious damage, too.

After putting the slide back on, I fired 17 malfunction-free rounds before noticing the trigger guard pin was half way out.

When I got home, I found the plunger was worn even worse than the 1970's plunger. See image 4277, next to a new plunger. In retrospect, it's a good thing my efforts to push the pin back in at the range wound up causing the pin to fall all the way out. Otherwise, I wouldn't have had an opportunity to inspect the plunger.

I ordered a second plunger and pin back in 2019, which are now installed in the 1971.

My hypothesis: plunger wear is what leads to the trigger guard pin falling out or becoming loose enough to shear.

[Randall_G]

A couple more photos showing the extent to which the plunger has been peened.

[hans22]

The trigger-guard pin on the P-64 is not a friction-fit or tapered pin. Its retention is almost entirely the job of the plunger and spring, which press against the pin and prevent it from drifting.

Once the plunger tip wears down, loses tension, or deforms, the pin no longer has a positive detent holding it centered. At that point it can:

Walk itself outward under recoil,

Shift enough to cause asymmetric stress,

Eventually shear or drop out.

So yes — plunger wear is a direct pathway to pin loosening or failure.

[manicmechanic]

Good catch!

[Rasmus]

The Trigger Guard Plunger and Spring does not press directly on the Trigger Guard Pin. It presses on the trigger guard itself just behind the pin, which in turn is displaced downwards into the center recess area of the middle of the trigger guard pin, locking it into place because it is barbell shaped.

I have also seen this plunger peen issue and am of the opinion that it gets peened partially because it is of a softer metal than that which the trigger guard is made, and because the P64's are desperately undersprung.

The slide bashes against the takedown lug at the front of the trigger guard with every cycle when there isn't enough recoil spring to slow it down. All the force of this is transfered down the trigger guard and into the pin area, moving it in a harsh back and forth motion. I also believe this is why some of them break.

You can feel this motion by pressing the front of the trigger guard back towards the trigger by hand and feeling the guard creep back. The hole for the pin is oblong in all the ones I have which I believe is by design although the oblong might grow even more so over time from this repetitive violent movement.

This motion is what probably wears at the pin, and also the tip of the plunger. I don't believe the wear on the plunger itself makes much difference because it doesn't change its length by more than a fraction of a millimeter and the spring inside there is VERY strong. OMG strong! It might make the rotation of the trigger guard a little bit less smooth when pulling it down to field strip but shouldn't make a difference in how tightly the pin is retained.

Pin retainment is more a factor of wear on the pin itself and perhaps residual hard cosmoline in there which is interfering with the design shape of the pin and not allowing the trigger guard to seat on the center section properly.

I truly believe than almost all of the issues people have with these guns originates with residual cosmoline screwing things up inside. I don't consider a P64 or any other firearm that was stored with cosmoline to be combat or self-defense ready until they have had a FULL detail strip and cleaning complete with an inspection under high magnification to ensure it has all been removed. I don't think very many of these guns ever get fully cleaned in this way.

I have certainly noticed this peening in the trigger guard plungers when they are disassembled and to fix them have just filed or sanded them back into a more smooth rounded shape in the same manner that the safety detent pins need to be rounded a bit to operate properly. I carefully chuck them up in a drill from the spring end and work them into sandpaper after knocking off the worst of the peened over metal with a flat needle file. I don't think they need such a pointy end to do the job anyhow. They were still working even in that crazy shape. Time will tell if a repaired less-pointy plunger will wear less than the factory shape. Mine was as bad as the ones in the photo yet had no wear in the pin or the trigger guard at all.

In none of the trigger guards I have inspected has there been ANY wear in the area the plunger contacts beyond the bluing being slightly worn off there even though the plunger itself was deformed. That's why I believe the plunger is made out of metal that is not hardened as much as the trigger guards themselves.

I personally believe the P64 is a bit undersprung, especially if the mainspring has been reduced to lower Double Action pull since the hammer cocking is part of the recoil-dampening action of these guns and reducing that spring is reducing the overall spring force slowing down the slide as it recoils. I run 22 pound Wolff recoil springs in all my P64s and would buy a 24 pound spring if they were to offer one just to try it out. Even with the 22 pound spring the slide still hits the trigger guard taketown lug pretty darn hard with every single shot with an 18 or 17 pound mainspring. I have run them both and have settled on the 17 because I like having a measured 11lb DA pull with 3.5lb SA.

No, I've never had a light strike or a magazine fall out. I feel that these issues are also linked back to cosmoline filth in the works gumming up things. Clean up those firing pins and Loaded Chamber Indicator channels, and polish those hammer struts.

[manicmechanic]

Nice diagnosis.

[Randall_G]

FWIW, the trigger guard pin on my 1971 had little to no wear. So, in this case, it wasn't pin wear that caused the trigger guard to come loose.

And, no wear other than finish on the trigger guard.

[Rasmus]

That is very interesting. For the pin to come out the holes in the frame and the hole in the trigger guard need to line up exactly. There needs to be either something out of spec on the pin because of wear/gunk to not allow the center trigger guard section to index properly and drop into the center section of the pin -or- there needs to be enough movement during recoil to allow the trigger guard to jump up and out of index against the spring tension while the pin simultaneously jumps sideways enough for the center index section to no longer line up when the spring pushes it back down.

Once the pin has moved sideways enough it could slide further sideways much easier with each following recoil until it simply fell out the side.

The spring is so strong that it takes a pretty strong strike to make it move far enough to allow the pin to become loose. Maybe the peened shape would not allow the trigger guard to not hold it firmly down as hard into the pin recess but I don't find this likely. It is simply pushing straight down. The only time the rounded point is at all helpful is when the trigger guard is pulled down the little cantilevered part of the trigger guard behind the pin would tip a little. But I could be wrong though and somehow the peened plunger might not be allowing the motions necessary during the firing sequence to keep proper tension on the pivot pin to ensure it stays indexed and tight. But IF I had to bet money I would say there was some hard to see cosmoline way up in the works gumming things up and slightly changing the size and shape of the pieces enough so that they are not fitting and sitting together exactly right. Or it could be that the cartridges are pretty hot and the recoil spring just isn't strong enough to keep the bashing of the slide into the taketown lug to a minimum.

I once had one single Wolf cartridge that was way over-hot from the factory (perhaps a double powder load) It was so hot that when the slide came back it hit the takedown lug so hard that somehow it knocked the entire trigger guard down and out of the way causing the slide to disassemble itself off of the rails and ride up over them as it came forward again . The case burst and blew one of the lugs below the breech face right off clean and the other one off half of the way back, leaving just a stub. It also blew the magazine right out the bottom of the grip and threw crap all over my arms and face. Good thing I was wearing eyepro.

The trigger guard snapped right back into place and wasn't harmed at all and the pin didn't pop out of place. The slide was sort of jammed half off and half on the frame with the pieces of lugs in there too wedging the works up tight. After I finally got them seperated I purchased a new slide and that gun has run fine ever since. That happened about 20 years ago now. I even shot it with the messed up slide trying it out and it fed and ejected just fine without the lugs although the cases bulge much more since they are not well supported without those lugs. I don't shoot Wolf any more and now days it can't be found to buy anyhow.