Revolver conversion to moon clips

[jar]

Originally Posted by Nathan

@jar….I’m not sure I understand what you mean..

As above. The goal in an emergency is to stay aware of threats and make sure you make the reload successfully. Getting everything right is more important than how fast you do it.

And about the Detective Special. The DS came out decades before S&W's "J" frames and is slightly larger with six rounds. It is between the S&W "J" and "K" frame size but I find it far more manageable to shoot than any of my "J" frame size revolvers regardless of maker. Also generally easier to find than the 2" barrel "K" frame revolvers.

[Nathan]

Well, order is in at TK Custom. I should get it shipped this evening…..maybe tomorrow.

Sounds like under 10 days door to door.

So, there are many moon clip holders for competition, but what for ccw? I’m thinking about something simple that clips over the belt that wraps around it to clip in and out, but allows grasping along the sides. Might have to reach out to my kydex guy and see what he has done or can do.

[jar]

Lots of clip type moon clip holders. The ones I use were made by ... you guessed it.

TK Custom.

[Nathan]

Wow! TK Custom! 5 days door-to-door….coming Tuesday

[Nathan]

Well, shot it after the conversion today. It is truly faster to reload. I need to try with a timer.

Loading and unloading is too much of a chore. I was hard on moon clips. So, I learned I need something to moon and demoon. Another $100! I ordered the BMT Mooner.

This J frame is getting out of hand. In retrospect, getting into moon clips is going to cost me $350ish…..on top of an expensive revolver and ruining my warranty. Possibly not my best choice.

That said, it really has transformed from something ok for ccw to being quite reasonable to train with.

[Don P]

Handheld loader and a homemade de-mooner (unloader) saves bunches of money.

[JimCunn]

I've lightened up three Airweight 637-2 J-frames using titanium .357 Mag cylinders reamed for 9mm and moonclips. I use Ranch moonclips at about $1.25 each. Three moonclip reloads will fit in a Walmart pill bottle, but I usually just carry them loose in my pocket - they don't bend.

Pretty much anything will work as demooner. Car keys, ballpoint pen, short screwdriver, etc.

[44 AMP]

Just to be clear, you took 3 S&W 637-2 guns, and had replacement cylinders fitted, using .357 cylinders cut for 9mm Luger with moonclips. Is that right??

[Screwball]

Originally Posted by 44 AMP

Just to be clear, you took 3 S&W 637-2 guns, and had replacement cylinders fitted, using .357 cylinders cut for 9mm Luger with moonclips. Is that right??

I did it with a .38 cylinder… not gaining anything by using a .357 cylinder. They are not beefier or stronger.

When you convert the longer chambering to 9mm, moon clips are required to headspace. No moon clip, the 9mm will fall too deep into the cylinder.

[44 AMP]

When you convert the longer chambering to 9mm, moon clips are required to headspace. No moon clip, the 9mm will fall too deep into the cylinder.

This is not my experience with 9mm Luger & .38Spl/.357 Magnum.

#1, if the 9mm chamber is properly cut, you do not need a moon clip for headspacing. The clip IS needed for extraction in a DA revolver, but not for headspace.

#2, cutting a .38 cylinder to 9mm requires more than just cutting the cylinder to fit the clips, it also requires cutting each chamber to take the 9mm round.

A 9mm Luger round WILL NOT go all the way into an unmodified .38Spl or .357 chamber. By the specs the 9mm case is .391" at the head, while the .38/.357 are .379". The 0.012" difference in diameter prevents the 9mm from going all the way into a .38Spl chamber.

[74A95]

Originally Posted by 44 AMP

This is not my experience with 9mm Luger & .38Spl/.357 Magnum.

#1, if the 9mm chamber is properly cut, you do not need a moon clip for headspacing. The clip IS needed for extraction in a DA revolver, but not for headspace.

#2, cutting a .38 cylinder to 9mm requires more than just cutting the cylinder to fit the clips, it also requires cutting each chamber to take the 9mm round.

A 9mm Luger round WILL NOT go all the way into an unmodified .38Spl or .357 chamber. By the specs the 9mm case is .391" at the head, while the .38/.357 are .379". The 0.012" difference in diameter prevents the 9mm from going all the way into a .38Spl chamber.

When they cut a 38/357 revolver chamber to fit a 9mm, they cut it with a ledge to properly headspace the 9mm round?

Do you have a converted 38/357 cylinder where they did that?

Thanks.

[44 AMP]

When they cut a 38/357 revolver chamber to fit a 9mm, they cut it with a ledge to properly headspace the 9mm round?

That is an interesting question, I do not know if they do, or not.

I don't have a .38 cylinder that has been converted to 9mm, never saw the point, or had any reason to justify the cost. What I do have is a .38 revolver, 9mm ammo, and the specs in my reloading manuals.

Now I understand that the specs are the standard maximums, and that each individual gun and the ammo can vary a bit from the specs due to intent, and manufacturing tolerances, and the actual SAAMI spec drawings have min/max tolerances.

That being said, and just going by the numbers I have, a .38 cylinder may not or may not have a ledge cut, specifically for the 9mm case to headspace on. It might depend on the actual tolerances obtained during the cutting, or on the preference of the smith doing the work. IF the cylinder is also being cut for clearance of the clips, there there is no need to have a headspace ledge, as the round will headspace on the clip. SO, the smith might omit it, as not needed. (if it is an extra step)

I do not know if the 9mm reamer will create the ledge when it cuts the chamber, or not. I am not familiar with the tool.

What I do know is the specs that I have show the .38Spl case as .379" at the mouth, and its a straight case all the way back to the rim. The 9mm case is .380" at the case mouth, and tapers back to .391" at the case head.

Cutting a 9mm chamber out of a .38 chamber MIGHT create enough of a ledge to headspace the 9mm on, I just don't know.

This situation is the opposite of using .45ACP in a .45 Colt chamber. In that situation, the auto pistol case is smaller in diameter than the revolver chamber, no headspace ledge can be cut, and clips must be used for headspace of the ACP round.

With the 9mm in a .38 chamber, the semi auto round is larger in diameter, so the chamber itself must be opened up to accept the 9mm round. That could create a headspace ledge I just don't know.

The other thing I do know is that last night I took a Colt .38, and dropped some rounds in to see what they did, in the gun that I have. .32ACP drops almost all the way through and stops with just the rim inside the mouth of the cylinder. .380 drops into the .38 clyinder with the case base about 1/4" inch below flush with the cylinder rear (firning pin won't reach it) and 9mm Luger rounds go about half way into the .38 chamber and then STOP with about have the case sticking out.

Personally, I feel that if you have a .38 cylinder reamed for 9mm, then from that point on, its 9mm ONLY. It might be possible to load and fire .38s in the 9mm cut chamber, (I don't know for sure) but I would consider doing so a foolish thing, as the .38 brass will certainly swell to fill the larger 9mm chamber, and might even split doing so, and even if it doesn't, it will be bulged and I would consider the case useless for reloading after that.

I have 9mm semis, and I have a 9mm single shot. If I wanted a 9mm revolver, I would get one purpose built in 9mm, (and probably a Ruger SA) and not convert a .38, but, that's just me.

[Jim Watson]

Since a .38 Special chamber is nearly cylindrical .380" with a plus tolerance and a 9mm case mouth is .382" with a minus tolerance, I see no way to generate a step to headspace on.
HOWEVER, the 9mm case is tapered and a closely reamed chamber MIGHT stop the round on that taper. But I would not want to bet on it.

The chamber reamer shops say their products will still shoot the original cartridge but they get kind of cautious about the load levels and warn against cases sticking with "high pressure" loads.

[74A95]

SAAMI specs for the chamber case mouth of the 9mm is .381 + .004, so anything between .381 to .385 meets specs

SAAMI specs for the chamber case mouth of the 38 Spl. is .380 + .004 so anything between .380 to .384 meets specs.

I'm ignoring the fact that they are different lengths down the chamber. So there is overlap.

Laid out:


.380
.381
.382
.383
.384
.385

So anything within SAAMI specs (red numbers show overlap) would leave only one example of the chamber having a lip.

[Jim Watson]

And then it is very shallow, not the pronounced step of a real 9mm gun.

I did once see a M940 reamed to take 9x23 and .38 Super. The former would be a stressful experience for both gun and shooter.

[74A95]

I asked TK Custom about headspacing 9mm after they cut the conversion. Their reply was:

Once machined for 9mm, you will HAVE to use a moon clip with 9mm ammo.

Eli Johnson


So, Screwball was correct.

[44 AMP]

I'd say screwball was correct for the conversion you had done by TK Custom.

[Screwball]

Originally Posted by 44 AMP

I'd say screwball was correct for the conversion you had done by TK Custom.

Mine was Pinnacle… so same for both.

[44 AMP]

Since it was pointed out how the tolerances of the existing .38 special chamber may be bored too large to allow a proper size "headspace shelf" when cut for a 9mm chamber, and since the ledge isn't needed when clips are used, I can see most shops not bothering to try doing it.

The only way to be certain an already bored .38 cylinder will have enough "meat" to cut the headspace ledge would be to bore it even larger and install a sleeve then cut that to the desired dimensions. Extra work not needed when using clips.

A better and probably cheaper route, if you wanted the conversion to work (fire) without using clips would be to start with a smaller caliber (.32) cylinder, and have it bored and chambered for 9mm, if possible.

Moot point if your plan is to use clips from the get go.