Forensic photos: Sherman Roller Action

There's been a bunch of threads on the Walt Sherman "roller action" where he used a ball bearing to reduce friction in double action. Unfortunately there hasn't been much detail. So to fix that we now err on the excessive detail end of things.

I bought a purported Sherman Officer Model Special (OMS) in 38spl a while back with Fishpaw grips, but hadn't had the courage to open it up.

Well that changes now! It was a pretty interesting set of internals that were in the gun.

Outside

Here's the outside:

Fixing endshake on 41 magnum python

I got a 41 magnum python conversion a while back, but unfortunately hadn't been able to shoot it b/c of excessive endshake. The difference between the max and min barrel / cylinder gap was well over .005 and, even worse, the minimum barrel / cylinder gap was about .00025 which made it seem likely the cylinder would slam into the barrel.

This weekend I finally got a chance to fix the problem by cutting out the cylinder, machining a bushing and putting it all together (with a bunch of fitting). I first did two shooter model 357s for practice (it won't be an easy matter to replace a jacked up 41 mag python cylinder) and then did the 41 magnum.

The process was not entirely smooth: I had to rip one bushing out and start over and the fitting was made excessively tedious since I did not record the minimum barrel/cylinder gap measurement before cutting out the cylinders. However, in the end all three colts now have < .001 endshake. Of course, they need to survive a bunch of rounds before declaring success. But, that's why god made next week :)

In promising news I've already done the identical fix to two pythons and a trooper when I went out to visit Frank Glenn. For these three colts it seems that things were done right: when I finally did a range test last week they survived 500+ rounds between them without issue. (They seem smoother too since they started at close to .0000 endshake, which forced the cylinder to travel through any binding rather than slip around it.)

OK. So let's get to it. We get excessive endshake when the collar on the cylinder is too short, and thus allows the cylinder to travel forward too far. You can stretch the collar using a special fixture but, unfortunately, that's a one time fix. We instead replace the collar by removing it and putting in a bushing in its place: you remove endshake by making the bushing sufficiently long.

Our algorithm:

1. Measure headspace to make sure we are comfortably above the minimum. If not, we can't do this fix (and likely will have to replace the ratchet).
2. Take the cylinder apart completely.
3. Put the cylinder in a 4 jaw chuck in a lathe and use an indicator to ensure that as it spins it wobbles by less than .0005".
4. Use a boring tool to cut a hole where the collar is until all (or just about all) of the collar material is removed.
5. Construct a bushing that reaches the bottom of the hole and has has a wide enough diameter so we can press fit it in the cylinder. The "collar" sticking out needs to be thinner than this part so it does not contact the barrel.
6. Press fit the bushing in.
7. Slowly remove material from the collar until the cylinder will fit in. Slowly remove more until it will turn. Be careful: just b/c the cylinder isn't turning doesn't mean the bushing is too long! It could be that 0 endshake is exposing other sources of binding.

We'll step through each step.

Cutting collar

Here's the cylinder and the carbide tipped boring tool we're going to use to cut out the collar and make a flat bottomed hole:

Forensic photos: 41 magnum Python by Jack Huntington

I've never seen any dissection of a 41 magnum python, nor really of a professional action job, so let's fix that!

I recently picked up a 41 magnum python conversion done by Jack Huntington (http://www.jrhgunmaker.com/). He was nice enough to chat on the phone. In his view it can handle a steady diet of 1,000 fps 41 mag loads. He also stated he worked at colt for a couple of years and has done around 2000 pythons. He did his version of an action job, including bending the trigger sear.

So, it'll be interesting to see what he did.

Last night I finally got to open stuff up. There were some interesting results, both in terms of what he did and what he didn't do.

Here's the gun (wrong stocks, I know):

Trip report: Frank Glenn gunsmithing lessons

I flew back Saturday after going to work with Frank Glenn on colts, mostly to learn how to eliminate endshake. In general, it's what you don't know that you don't know that causes the most harm, so having someone that knows what they are doing can be priceless.

1. If you don't know an area it's very easy to do something stupid that seems fine. An example from when I picked up a file for the first time a while back: filing by sawing back and forth! Never occurred to me that it was wrong, and it's so stupid most gunsmithing books wouldn't even think to say "don't to that!"
2. It's easy to have assumptions you don't think to check that will make things very hard. An example from this trip: I thought a gun had an endshake problem b/c the cylinder would contact the barrel, when in fact the factory had simply filed the barrel unevenly, leaving the right end too high. Didn't occur to me that a fairly pristine gun from the 50s would have a factory issue. Trust nothing (or "check everything") otherwise you'll get really confused.
3. There's one real book on colt DAs and it's missing a bunch of stuff, unfortunately. (Dfaris stop writing fiction and do an update!)

In any case, the regime was simple: I flew out 4 colts with alleged endshake problems, my dad drove down two that weren't working, and I spent three days getting through them with Frank. I also learned how to curve the sear on a trigger using a torch so that you can eliminate stacking.

What we have to work with

Here's my initial four (dads' are not pictured). A really nice handling old style 357 trooper, a bull barreled python, a snub python, and a 1957 python that someone jacked up the front sight on and sold the checked grips:



All were selected to have endshake issues: excessive play or, worse, direct contact of the cylinder and barrel face.

Part II: tuning a (now very tight) 2.5" python

NOTE: the stuff below is just for entertainment. I am not suggesting this is what you should do or how you should do it. Consider it a fast way to ruin your gun: DO NOT DO IT ON YOUR COLT! If you see something where I am messing up, please point it out!

So, after fixing the snubby in Part I
http://coltpython.blogspot.com/2009/05/part-i-fixing-most-loose-25-python-ever.html we try to do something about it's really bad action. Heavy, uneven, and gritty.


Smoothing it is pretty easy.

This is what we have to work with:



Anything that touches anything is a candidate for causing grit. And from the looks of the parts its not mystery why it could feel like there was dirt in there. The corrosion level is impressive. And the tooling ridges aren't anything wimpy either.