I built up a new .45 using a collection of great parts from Wilson Combat, Ed Brown, Kart, etc. and put ~100 rounds of hardball through it last weekend.
The gun shot great, but one thing happened about 10 times - the slide "stuck" in the rearmost position when cycling. A gentle nudge with the thumb sent it forward again.
I've never experienced this before, and don't know where to start the debugging process. Any ideas?
You don't say what your set up is...
Same thing happened to me on my Colt when I replaced the Recoil Spring with a Wilson 18# and added a shock buff. I took out the shock buff and shot another 25 with the slide getting stuck back twice more. Then I cut one coil off the new spring and all was good.
Remove the recoil spring, pull the slide fully aft and see how much up & down play there is in the aft end of the barrel.
Good point Doublenaught...
Recoil spring is a bone stock 18# from Wilson Combat.
Quote:
The gun shot great, but one thing happened about 10 times - the slide
"stuck" in the rearmost position when cycling. A gentle nudge with the thumb
sent it forward again.
That happened to me when assembling a gun out of parts from mixed origins.
Suggestion -- strip the frame and slide, and just install the bare slide on the bare frame. Cycle the slide manually, but "briskly." See if it sticks. If so, check two things:
First, the slide may simply be fitted a tad too tightly to the fame. A couple of light swipes with a file along the outside of each frame rail may clear it up.
Second, mark the front sides of the frame rails with a Sharpie marker (or Dykem blue, if you have it), then cycle the slide manually a few times. Inspect the rails. See if the marker/Dykem has been removed. The fronts of the rails may not have enough bevel, and may be jamming into the ends of the slots at the forward end of the slide. If that's the problem, increasing the bevel is a lot easier than hogging out the slots in the slide.
Start with the slide and the frame. Field strip, remove the barrel & recoil spring. Try running the slide full rearward; see if it sticks. If it does, the front corner of the frame rails may be wedging into the back of the dust cover. If so, relieve the area on the slide where the frame rails can meet the slide.
If that's not the problem, check the disconnector/slide interface. The slide may be catching on the disconnector. If the disconnector is functioning smoothly, the bottom front edge of the disconnector rail (bottom of the slide) can be very gently smoothed.
Generally one or the other of the above is the issue. If not... it gets a little complicated.
Don't forget that when the gun is in use and the slide is fully aft on the frame, the recoil spring guide's plate/flange is in between the recoil spring plug tunnel of the slide and the impact abutment of the frame. So when it's just the slide and frame (no guide) the slide will try to go aft farther than normal by the thickness of the plate (about 0.086") and perhaps stick - and nothing may be wrong!
There is virtually zero vertical play on the slide in any position. This is a brand new frame/slide combo and is very, very tight.
I removed the recoil spring and cycled the slide 100 times or so. Seemed OK, but there were a couple of sticky spots, not just the full aft spot. I fully stripped the gun and used valve lapping compound on the frame rail/slide interface. That highlighted a couple of "hot spots", so I continued working with the lapping compound until the slide would smoothly slide off the rails if I pointed the muzzle end down. I could get it to stick aft by sliding the slide too far back, as you mentioned, but that's farther than it would travel during normal cycling.
Everything is now cleaned, oiled (Gun Butter), and back together.
Off to the range!
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There is virtually zero vertical play on the slide in any position.
What I'd asked about was not the slide/frame play but the vertical play at the back of the barrel when the slide was all the way back. Insufficient clearance between the barrel and inside of the slide when the barrel's linked down can also cause a slide to stick. Especially because if the barrel does not drop down fully it won't be parallel to the frame top and will be higher at the hood end. Please re-read Post #3.
Q: When the slide is fully aft, is there any detectable vertical play in the aft end of the barrel?
Q: Have you done the linkdown timing tests on this gun?
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I fully stripped the gun and used valve lapping compound on the frame
rail/slide interface.
My heart sank when I saw this. Automotive valve compounds are almost always silicon carbide grinding compounds - even the finest stuff. And silicon carbide particles tend to embed themselves in the surfaces and are nearly impossible to remove. This means no matter how well you think you may have cleaned them off, some will remain and tend to grind away at the surfaces for a long time. Aluminum oxide is the proper lapping compound to use on sliding surfaces.
Q: Was the abrasive in your compound silicon carbide or aluminum oxide?
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I could get it to stick aft by sliding the slide too far back, as you
mentioned, but that's farther than it would travel during normal cycling.
Q: Can you get it to stick with the guide rod installed?
OK! The gun shot well and functioned smoothly for 100 rounds, but I'm not declaring victory.
I think there might be a linkdown problem as described by Niemi24, because there are a couple of "hot spots" on the topside of the barrel that extend all the way aft. I'll do all the timing tests today.
The valve grinding compound was water-based Silicon Carbide, which I cleaned off in an ultrasonic cleaner. Based on your note, I've ordered a tub of 500 grit water-based Aluminum Oxide lapping compound from American Lap. Fortunately for me, if the Silicon Carbide causes long-term problems I've only messed up a carry gun, not one of my Bullseye guns.
More as it happens.
Jim... just a suggestion. Check out Brownells on the web as they sell the proper lapping compound. Buy the light grit... works great.
Don't know if this helps much, but it's an attempt to illustrate what I was trying to say in Post #7:
Closing this thread out.
I installed a .001" longer barrel link that relieved the top side of the barrel away from the slide in the fully aft position. Between the lapped frame/slide interface and this link change, the occasional sticking in the aft position is done.
So, the sticking was most likely due to the slight jamming of the barrel against the underside of the slide, versus anything related to the frame/slide interfaces.
Another 100 rounds downrange yesterday with perfect function. So now I'm declaring victory. I'm so delirious with joy that I've now completely torn the gun apart, and delivered it to a great shop here that does Cerakoting. The next picture I post will be of a Flat Dark Earth carry gun with Graphite Black bits and pieces.
Thanks for all the help and guidance. Much appreciated.
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I installed a .001" longer barrel link that relieved the top side of the
barrel away from the slide in the fully aft position.
You must have also enlisted the services of a medicine man because all a longer link can ever do is get the top of the barrel closer to the underside of the slide. A sufficiently longer long link will do this by preventing the barrel from falling all the way to to the bed.
Another way of looking at it is that if the link is too long, when the barrel links down it will remain in compression, hold the barrel up off the bed and reduce the barrel-to-slide clearance. A shorter link will thus allow the barrel to fall all the way down to the bed and increase the barrel-to-slide clearance.
There must be some other reason for why the clearance increased.
Of course you're right. It was shorter, not longer. It was also "different", which may have contributed to it working smoothly now. Regardless, the gun is now in an nice ultrasonic bath getting prepped for Cerakote...