Colt Forum banner

1 - 9 of 9 Posts

·
Registered
Joined
·
73 Posts
Discussion Starter #1
It's kind of common knowledge that Colt slides made prior to (I have heard varying dates... I'm guessing 1947) were not heat treated. This resulted in the slides peening, cracking and the slide-stop notch would cut out quickly. The "solution" has been "spot hardening". There are varying opinions regarding WHAT should be hardened. Quite consistently, the spots mentioned are the slide-stop notches and the front 1/3 of the slide.

Through the years I have spot hardened around 50 slides give or take. It's been a highly successful practice. I quit doing it for customers a couple of years ago, but I still do the occasional one for myself. Years ago, before I had even done 10 slides I began hardening additional areas. It resulted in very tough slides. I hardened the slide lugs, I hardened the bottom corner of the breech-face, I hardened the sear-disconnect groove, all in addition to the front 1/3rd of the slide and the slide stop notches. I would heat to red/slight orange, then oil quench. I had a particular order regarding what got hardened when, because when done right, hardening the next spot would then temper the previous spot, with the last hardened spot being the only area requiring a dedicated tempering. I never warped a slide. I have never had a slide break. One last thing, do not try this on your own. If you do, you take the wrap if the slide breaks and hits you in the face!

As I previously said, I've never had a slide break, until the last one. I always thoroughly inspected the slides before spot hardening. I was looking for cracks. I couldn't find any on this slide. Using an extremely bright light and a magnifying glass, the slide looked fine. I executed my hardening procedure. Now obviously, once this is done the finish is utterly destroyed. I gave the slide a quick bead-blast finish and re-blue. I completed my gun and took it to the range. I fired the first few shots from the hip wearing a leather glove. Whenever I spot harden a slide, that is standard operating procedure for me! A whole magazine later, it was fine.

Time for some target work! I loaded the mag, jacked one in the chamber, aligned my sights and squeezed the trigger. BANG! Thankfully, I was still wearing the leather gloves. The slide broke. It broke big time, up by that front 1/3rd. There is a rather large part of the slide I still haven't found. My right hand was bruised. I went back to the shop.

Where did I go wrong? Once I settled in and closely examined things it became immediately apparent. Where the steel broke, internally, it was literally corroded. This slide had cracked a long time ago and I did not see the crack. The corrosion was IN the crack indicating a crack from some time ago. I looked that slide over so thoroughly it borders on unreal, yet I did not see the crack. The crack was on each side the sides of the slide then jetted forward on the left side. It should have been visible when the front 1/3rd was heated to red/orange, but no, I didn't see it. The corrosion revealed itself as starting from the inside of the slide, in the crack, moving outward. The crack likely was neatly tucked away in a machine mark making it highly difficult to find. If the frame hadn't bent, I would have probably been smacked in the melon by a fast, heavy metal object.

Now for Part 2. I have a microscope. It's no toy, I bought it years ago at an auction. It came from a hospital. I use it to examine grain direction on gun parts. I have additional slides, many of which are old, GI slides. When examined under a microscope, one of my old GI slides had a crack inside of it, very similar to what I believe the broken slide had. It went in the trash.

From here on I will be examining GI slides with my microscope prior to hardening; or I may just quit using them all together. This is the first time I have ever had a problem though. I have rejected slides because of cracking. I have never had one with a hidden crack though. I hope.


Broken 1911 Slide.jpg
 

·
Registered
Joined
·
10,291 Posts
The front of the slides were tempered beginning in 1937, and the slide stop notch hardened beginning in mid 1943. Fully hardened slides were being tried before the end of WWII. The military wasn't having a problem with cracked slides, but hardened the front of the slide and the slide stop notch to prevent battering in this area. There was also a hardened plug installed in the breech face, and the hardened slides were proposed to speed up production by eliminating these separate operations on the slide.

Replacement military slides from Colt had fully hardened slides beginning in the early 1950's. Most of the replacement Colt slides I have seen are dated around 1952 on the packing.
 

·
Registered
Joined
·
488 Posts
That sounds like the problems experience in damascus twist steel shotguns. Black powder corroded the bbls from the inside, hidden along the wrap lines.

Charlie
 

·
Registered
Joined
·
13 Posts
Referring to the photo of your slide. Is that a common area to find cracks? Would magnafluxing work to identify cracks? Thanks
 

·
Registered
Joined
·
1,567 Posts
What is your opinion on the military's hardening of slides to prevent cracking? On the "other" forum it is gospel that hardening was done to prevent cracking (as well as to prevent galling). Is there any scientific or engineering evidence that hardening does help reduce the cracking problem on soft slides?
 

·
Registered
Joined
·
587 Posts
If you are a "amateur" trying to heat treat metals of unknown composition you are running blind and Can do more harm than good. That is just the way it is. Looked into doing mine 35 years ago (going to customize it) and after several conversations with the Colt SME in this area was informed not to.
 

·
Registered
Joined
·
73 Posts
Discussion Starter #9
I can assure you my methods are more detailed than I typed out. As I said, I have never had a slide break. I have a 1911 with thousands of rounds through it since spot-hardening the slide. The slides I have "out there" have been fine. As I said, I don't do it anymore (unless I do one of my remaining slides for myself). Basically, a decent slide can be purchased for so little money now it doesn't make financial sense to pay what people are asking for the old Colt slides and then pay what's required for spot hardening. I have discovered a way to check for cracks that seem pretty darn reliable. With the slide hanging free, a "speaker type device" that is only 3/8" in diameter is attached to one end of the slide. A miniature microphone element is attached to other end. Do this one each side (slab) of the slide. Using a frequency generator send a 10khz signal to the speaker element at a level of -40db. The microphone element should display a 10khz signal on a frequency counter at a level of -50db. If the signal is not detected or is extremely weak, it's likely that the slide is cracked. A gun dealer close by has a pile of cracked slides. I tested 8 slides using this method. None of them would pass the 10khz frequency from speaker to mic. The slide must have the ability to ring. When the have even minor cracking, they will not ring. I will use this in the future. There are many physics-related reasons why this works.
 
1 - 9 of 9 Posts
Top