HomeSmith Tuneup: Pushover

Shotguncoach · #1 03-10-2024, 03:15 AM

Today's project is a Model 66-1 with a bad case of push off, a messed up trigger job, and a damaged rear sight.

Project Name: Pushover

My FFL brought this one out to show me when I stopped by to pick up another 4" Pre-24 and a 6" 624 from a recent auction. He had purchased this 66-1 for himself online and was unhappy with the trigger. The way he described it was "super super light single action and a double action pull that was complete......" well, I can't put that word here, but you get the idea.

After verifying that it was clear and that the double action pull really was horrible, I cocked the hammer, removed my finger from the trigger guard, and pushed on the hammer with my thumb. Down it went. Classic pushoff. We talked a bit and it ended up coming home with me.

With my emotional support llama standing by and Mr. Kuhnhausen ready to help if needed, it was time to jump in.

Shotguncoach · #2 03-10-2024, 03:28 AM

The first order of business was a full inspection.

In addition to the push off issue, this poor guy had been dropped and of course it landed on the rear sight blade. The left side was bent and when viewed under a magnifying lens it became apparent that it was also cracked. No bending this one back into place.

Other items noted were that the left stock panel was cracked and there was a bit of rubbing on the left side of the hammer.

The cylinder was free spinning and rotated easily.

Timing was good on all 6 chambers.

No yoke bind was observed. In fact the yoke seemed a bit loose. We'll get farther into that later.

Scratches were noted in the frame and on the sideplate at the top of the stocks, as if the gun had magna stocks at one time.

The strain screw was tight.

There was a small dent in the barrel serrations at the rear edge of the front sight ramp, and the serrations were full of gunk.

The bore and all 6 chambers were clean and in good shape.

The single action trigger pull was measured at 1 lb, 6 oz. Double action pull was 11 lbs, 8 oz.

Hammer tension was 68 oz.

Theory: someone botched a trigger job and went way high with the hammer spring tension to cover up the push off enough that the gun could be sold.

Shotguncoach · #3 03-10-2024, 03:42 AM

The cylinder gap without a wedge measured .007". With a wedge in place the gap was .002", giving us .005" of endshake.

Measured with a trigger pull gauge, the amount of tension required to make the hammer fall without touching the trigger was 24 ounces. It would barely stay at full cock by itself. Dropping the gun butt first onto the bench from a height of 6 inches was enough to make the hammer fall.

Shotguncoach · #4 03-10-2024, 03:51 AM

Some slight screwdriver damage was noted on the rearmost sideplate screw. All of the sideplate screws were loose. The sideplate came off easily and revealed what appeared to be a nicely clean interior mechanism.

The insides were moved to the outside and the trigger/hammer sear surfaces were examined under a magnifying lens. The trigger bevel appeared to have at least 3 angles (possibly 5 depending on how you want to count) cut into it and was almost round when viewed from the side. The hammer looked OK to me but was suspect simply because of the pushoff issue.

Shotguncoach · #5 03-10-2024, 04:11 AM

After reading the description from Armorer951 and Mr. Kuhnhausen on the "benchtop" method of recutting the trigger bevel to correct pushoff, I attempted to recut the trigger. I'm not sure if I simply didn't go far enough or if the trigger was just too far gone to be fixed, but the pushoff issue did not change. I think I actually made it worse. Edit: The picture is just for illustration. I placed the trigger and stone directly on the benchtop and not on the shop towels to do the actual cut.

It was time to go to plan B. (Or really what was plan A all along....I wanted to try fixing the trigger but didn't have much hope after seeing how round it was)

Plan B involved a parts kit for a Model 67 that I picked up around the first of the year during a sale. The parts kit contained a semi-target hammer and a smooth trigger. My plan was to replace both pieces to remove any doubt about the original hammer.

The original hand was moved from the 66 trigger to the 67 trigger and a test fit was done to check the timing. Fingers crossed.......and it worked! Yay me. The emotional support llama smiled. Since that part worked, the new hammer and the original hammer spring were installed, the strain screw tightened, and push off was tested.

We win Gracie. No pushoff at all, no matter how hard I pushed. I even tried lightly tapping with a brass hammer and it was rock solid. Very cool. (Edit: see the post from Armorer951 down the thread. This was not a good idea)

Let's put the sideplate on and do a full function check. Hammer block in, sideplate on, screws tight.....and now it's completely locked up and the action won't move at all.

The emotional support llama was not happy with me.

Loosening each sideplate screw half a turn allowed the action to almost cycle but it was tight. Time to take it apart again.
Hopefully there would be some marks inside to tell me what I had done wrong.

Can you see it?

Shotguncoach · #6 03-10-2024, 04:23 AM

Yep, the rookie made a rookie mistake. I didn't fully inspect the replacement hammer before I installed it. The pin that retains the double action sear was not fully seated and was sticking out the right side of the hammer enough to rub on the sideplate. A few taps with a punch moved it into the proper position.

The insides were moved from the outside back to the inside (again) and we tried again for the function test. This time it passed. The timing was on, and both single and double action worked properly with no pushoff or binding.

I suppose I could have stopped there, but I wanted this one to be in good shape. The insides were moved outside one more time and the fluff-and-buff was started.

Shotguncoach · #7 03-10-2024, 04:33 AM

The inside of the frame appeared to be "as delivered" and was full of tool marks. These were addressed with the small end of a ceramic stone to knock off the high spots. This was a "smoothing" and not a full polish.

There were a couple of jagged edges on the frame and sideplate that were also smoothed out while I had the stone handy.

The bolt was smoothed on every side, and the thumbpiece was stoned to remove some burrs that had been marking up the frame.

The trigger was touched up with a stone at the interface with the cylinder stop to help with a smooth reset, and the face of the trigger was polished with 2000 grit sandpaper.

The rebound slide had some pretty good chatter marks on the bottom but there were deep enough that they weren't going to touch anything. I've heard of people cutting grooves into the rebound slide to reduce the surface friction area...maybe this is just the poor man's version of that.

Shotguncoach · #8 03-10-2024, 04:43 AM

With the fire control components back in their homes and living happily together, it was time to go back to the cylinder and yoke assembly.

The yoke was checked for straightness and passed.

Yoke play was checked and some slop was found. There was .0025" of clearance between the yoke flange and the frame. A .002" yoke shim was stoned to remove any burrs and installed on the yoke. A bit of galling was observed which may be helped by the shim.

Shotguncoach · #9 03-10-2024, 04:47 AM

The spiffy Power Custom ejector rod straightness fixture was set up next. I didn't really need the dial indicator to tell me that something was wrong here....the rod was visibly wobbling.

The actual amount of runout was .013". This time I remembered to mark the high spot so that I wasn't just bending the rod back and forth. After a few tries we were at .003" of runout. Good enough.

Shotguncoach · #10 03-10-2024, 04:59 AM

The handy-dandy Power Custom ejector rod unscrewing and rescrewing tool was used to disassemble the cylinder. Three empty .38 cases were used to support the ejector star during all unscrewing and rescrewing operations.

My notes showed .005" of endshake, so a .003" shim was selected from my Shively assortment and verified with a set of calipers. This shim was also stoned to remove any edge burrs. As a side note, when you drop the shim onto a smooth surface and don't want to bend it trying to pick it up with your fingernails, the little blob of grease on the end of your grease syringe makes a dandy shim picker upper.

This is where I think I made a mistake and didn't catch it until I rechecked the final endshake. I used a .003" shim to correct the .005" of endshake and leave .002" for clearance, but I forgot that I had also put in a .002" shim on the yoke. I should have shimmed the yoke first and then checked the endshake. I probably would have left it alone. As it is, the gun now has .001" of endshake which may not be enough. I'll test it on Sunday and if it binds when it gets dirty I'll swap the .003" shim for a smaller one or just take it out completely.

The rear gauge came out perfect, with a .060" gauge able to fit and the .068" gauge not even trying to go in.

Shotguncoach · #11 03-10-2024, 05:10 AM

We were almost done...all that was left to do was replace the rear sight, do a good cleaning on all the various grooves and serrations that were full of glock, and do a final function check.

The sight swap was very easy and the replacement sight assembly from the model 67 parts kit just slipped right into place.

Hammer tension with the new setup was 56 ounces, so I knew that I could improve the trigger pull a bit by shortening the strain screw. A few quick spins in a drill motor against a file and the strain screw was shortened with a nicely rounded tip that would fit into the Wolff hammer spring that I had installed earlier. (A Wolff 14lb rebound spring was also used...I forgot to mention that.)

The modified strain screw produced a hammer tension of 50 ounces, and combined with the fluff and buff and the Wolff springs our final single action pull was 2 1/2 lbs and the double action pull was 8 pounds. No pushoff was observed.

Notice that I did NOT do anything at all to the sear surfaces on the replacement parts. I may do that someday, but without a baseline of how it works as-is I wouldn't have anything to compare against. We'll see.

It's time for a range trip to see if it binds up with only .001" of endshake. Stay tuned....

OutAtTheEdge · #12 03-10-2024, 10:45 AM

Nicely documented, Shotguncoach. Reminds me of a pre-14 Target Masterpiece I picked up a couple decades ago that would also push off. The gun was actually shootable that way, but I just couldn't sleep at night knowing it wasn't right. The tough part was finding the appropriate replacement parts, but once I had them in hand, Mr. Kuhnhausen got me through it just fine.

Protocall_Design · #13 03-10-2024, 12:28 PM

That will be a very nice gun now. Another informative writeup with quality pictures.

Any time the ejector rod is loose or taken off, you need to recheck the runout after tightening/reassembly. The threaded coupling is where any crookedness comes from.

RMFnLA · #14 03-10-2024, 01:09 PM

Great write-up, as usual, but you missed a great opportunity to replace the hammer and trigger with cased parts.

That’s what I did on my Boston PD 64-3, love the result.

Shotguncoach · #15 03-10-2024, 01:31 PM

Quote:

Originally Posted by RMFnLA

Great write-up, as usual, but you missed a great opportunity to replace the hammer and trigger with cased parts.

That’s what I did on my Boston PD 64-3, love the result.

I'm saving those parts for other guns.

I had a set of stainless parts that matched, so here we are.

Shotguncoach · #16 03-10-2024, 01:34 PM

Quote:

Originally Posted by Protocall_Design

That will be a very nice gun now. Another informative writeup with quality pictures.

Any time the ejector rod is loose or taken off, you need to recheck the runout after tightening/reassembly. The threaded coupling is where any crookedness comes from.

Good point, and thank you. I've been doing the runout test first. I'll switch my order of operations so that it comes after everything else is done.

armorer951 · #17 03-10-2024, 03:54 PM

Nice, thorough work. Very instructive for the rest of us too.

Be sure not to use too much pressure when testing for push off, or when checking a repair. Those surfaces are hardened, and can literally break off if undo pressure is used. I kind of cringed when you said you tapped the hammer with a brass hammer.

Shotguncoach · #18 03-10-2024, 04:04 PM

Quote:

Originally Posted by armorer951

Nice, thorough work. Very instructive for the rest of us too.

Be sure not to use too much pressure when testing for push off, or when checking a repair. Those surfaces are hardened, and can literally break off if undo pressure is used. I kind of cringed when you said you tapped the hammer with a brass hammer.

It was a light tap...not even the full weight of the 4 ounce hammer. I've read in other threads about police departments checking for push off that way. That doesn't necessarily mean it was a good idea though.

I'll just use my thumb from now on. I put a note in the original post to reference your advice. Thank you.

Shotguncoach · #19 03-11-2024, 01:17 AM

For just dropping the rear sight on the initial POI was pretty good. That's 158 grain JHP .357 on top and 158 grain LSWC .38 on the bottom, both fired two handed single action at 10 yards. I ran out of time and wasn't able to do a final sight in, but it looks like 2 up and 1 right should about do it for the .38 load.

It functioned just fine with the minimal endshake even shooting lead bullet reloads with Bullseye powder.

Edit to fix another darn sideways picture. Someday I'll figure that out.

schutz5 · #20 03-11-2024, 01:45 AM

Thanks for this write up shotguncoach!