Model 646 Question

[Pizza Bob]

I was fortunate enough to come across a S&W model 646 and in doing some research I noticed that some accessory sellers (Brownells in this case) offer full moon clips in two different thicknesses. I'm assuming there must be a large enough variance in extractor groove width, among the various ammo manufacturers, that using a clip of the proper thicnkess provides better headspacing. Does anybody know which manufacturers correspond to which thickness of moon clip?

Here's my new toy...


Adios,

Pizza Bob

 

[Palmetto Sharpshooter]

I wish someone had that answer. I sure don't. BTW: You may want to put some nice soft rubber grips on that before you shoot it. Mine is a beast.

 

[TSQUARED]

Bob,
I have the same gun and use the Ranch Products moonclips. The last time I ordered they were $75 per 100. You can order by obtaining their phone number form their website and calling them.

I was fortunate enough to come across a S&W model 646 and in doing some research I noticed that some accessory sellers (Brownells in this case) offer full moon clips in two different thicknesses. I'm assuming there must be a large enough variance in extractor groove width, among the various ammo manufacturers, that using a clip of the proper thicnkess provides better headspacing. Does anybody know which manufacturers correspond to which thickness of moon clip?

Here's my new toy...


Adios,

Pizza Bob

 

[David Sinko]

Is the cylinder bored straight through? Being a dedicated .40 S&W revolver, it should have a lip in each chamber which does the headspacing. Will the chambers hold loose rounds and fire without the moonclips? If you are firing .40 S&W in a 610 then yes, you will be headspacing on the moonclips. And even then I still don't understand why you'd need two different thicknesses of moonclips.

Dave Sinko

 

[Pizza Bob]

Dave:

No there is a shoulder in the chamber, so, theoretically, you are correct. Wit the exception of extraction, you should be able to shoot this "clipless". The moon clips make headspacing more reliable, since even new, factory loaded ammo may have cases of the minimum (or below) length. I think, just as a 1911 most often headspaces on the extractor, the moon-clip revolvers headspace on the clip. And, I too, am at a loss as to the reason for the different thicknesses.

Adios,

Pizza Bob

 

[OKFC05]

I bought one of the 646s new when they came out on the second run.
I immediately had reliability trouble (FTF) with the thinner moonclips and had to use the thicker ones.
You can buy either at
Welcome to TK Custom.com & Moonclips.com

My 646 will NOT fire without the moonclips. According to S&W, the production 646 was purposely overbored and is not intended to be fired without the moonclips.

I put a set of Pachmayr Pro-Grippers on my 646 because the original grip was too small for me.

I shoot the 646 with reduced 120 power factor loads in ICORE and major power (165) in IDPA/ESR. It is very soft shooting with 120 PF, and more of a handfull with 165 PF.

 

[Palmetto Sharpshooter]

I shoot the 646 with reduced 120 power factor loads in ICORE and major power (165) in IDPA/ESR. It is very soft shooting with 120 PF, and more of a handfull with 165 PF.

What is your powder charge? TY

 

[S&W-Keeper]

Try some of the plastic moon clips from Rimz,I like them a lot. You don't need a demooning tool.

 

[BUFF]

And even then I still don't understand why you'd need two different thicknesses of moonclips.

Dave Sinko

I forget which is which, but the extractor groove on one brand of .40 brass is either much thinner or thicker than the other two major brands (Federaal, R-P, W-W).

 

[WC145]

Buff is correct.

I've fired mine without moonclips but ignition is spotty. The gun was designed specifically to use them. I've bought moonclips from S&W for it but if I recall they only offer one size now.

 

[David Sinko]

What does "purposely overbored" mean? And why would it be necessary to do this to a 646?

I have seen wide variation in rim and extractor groove thickness in .45 ACP and 9mm brass. All three of my 625s and 940 function perfectly with only a single thickness of moonclip and any and all types of brass loaded into them. These revolvers also fire with complete reliability without the moonclips. The worst moonclip gun I ever owned was a 627-4 8x.38 Super that was worthless without moonclips and obviously deliberately designed to function this way. While some brands of brass fit much tighter into the moonclips than others, it still used only one thickness of moonclip and headspacing and ignition were fine.

All the moonclip guns that I own today have hammer mounted firing pins. The revolvers that have erratic ignition without and often even with their moonclips are those with the frame mounted firing pins. I'm more inclined to think that these problems are gun related and not ammo or brass related.

Dave Sinko

 

[OKFC05]

What does "purposely overbored" mean? And why would it be necessary to do this to a 646?

Having fired 625s without moonclips, I called S&W customer service and asked why my new 646 would not fire without moonclips. They said the cylinder was bored too long for .40S&W and too short for 10mm, therefore I would have to use the moonclips and shoot .40 S&W.
They didn't say why it was made this way, and I was too surprised to ask. Your guess is as good as mine.

I asked them to reduce the headspace and cylinder gap, and they did tighen it up considerably at the factory. Haven't had any FTF problems since, but I do have to use moonclips. It has the frame mounted firing pin.

 

[OKFC05]

What is your powder charge? TY

For the lighter load, I drop down to 4 gr of 231 under a 180gr Berry. Could drop lower and still make ICORE PF in the revolver, but I also use the load in another gun. It will operate a .40 Sigma, and it makes a delightful plinking load in it.

 

[WC145]

I was under the impression that since the 646 was original designed for competition, like the 627-4 .38 Super, it was meant to be used only with moonclips.

 

[David Sinko]

A shooter at the match last night was using a 646. He said his fires with complete reliability without using moonclips and there is no difference in performance with the two different width moonclips. So it appears there is a very fine line here in regard to what works and what doesn't work and S&W is not capable of consistently holding that fine line, at least not with this model.

Dave Sinko