The Unofficial P64 Resource Forum

I'm having a hard time understanding how the hammer spring affects the "last round mag drop" issue reported by some folks.
My 1969 P-64 dropped the mag on last round 6 times in a row with Wolff 22 lb recoil spring and 18 lb hammer spring. At this time I do not recall if it dropped any mags with the original recoil and hammer spring. I do know it jammed (stovepipeed" several times with Silver Bear ammo. Brown Bear was fine.

Changed the hammer spring to 20lb and of 6 mags fired, mag dropped (and slide did not lock back) on mags 1,2,3,6 ??? This is happening with the "old style" original magazine that came with the pistol.

Then noticed with the slide off and inserting mag, it sometimes slips past the tab on the inside of the SLIDE STOP LEVER. I did a thorough cleaning in the area around where the slide stop lever and spring seats in the receiver and it seems to happen less, but unless I hold the receiver end of the slide stop lever in, the mag occasionally will slip by. When that happens, the magazine follower fails to push up the slide stop lever which when "up" locks the slide back after the last round has cleared the mag. I see from the scrapes on the slide stop lever that the slide apparent holds this piece in place.

Is a new slide stop lever perhaps in order? Does a heaver hammer spring perhaps apply more pressure to the mag causing it to stay closer to the slide stop lever?

I also can see it is imperative to keep magazines clean. If the mag follower gets gummed up and does not go all the way to the top when empty, or the mag spring gets weak, the slide stop lever will not be pushed up and the slide will not lock back after last round fired.

I really like this pistol as it is a very nice piece of history although I will not "carry" it with this malfunction. Any thoughts are certainly appreciated.

I wonder about that also as I have th heavier recoil and lighter hammer springs but don't have that problem.

I'm beginning to wonder if the issue you describe (which folks tend to experience when going to WEAKER hammer springs) is because the weaker hammer spring allows the slide to slam back a little faster...perhaps faster than the magazine follower can reach the top of the magazine! This really may be the trick here.

In your case it sounds like it could be the magazine spring itself. I don't think a stiffer hammer spring will necessarily hold the magazine up to the frame any tighter, as it's really just a latch, not much in the way of upward pressure.

Do you have a spare magazine you could try?