S&W 646

K

Kenneth L. Walters

New member
I recently purchased an S&W Performance Center model 646 revolver. It is chambered in 40 S&W and uses moon clips. The gun came with two little plastic bags contains the clips. One was marked 0.042 and the other 0.035.

If you don't use any moon clips the gun functions fine but, of course, extraction must be done manually. If you try to use the 0.035 moonclips you can not even close the cylinder. If you try to use the 0.042 moonclips the cylinder will close but the gun occasionally freezes up when the cylinder tries to rotate.

I also bought some moonclips from moonclips.com. With these the gun ALWAYS freezes up when it is fired.

Anyone know of a solution to this problem?
 
My gun had some of the same problems and I worked them out. Just don't remember what exactly I did. One thing I have noticed about the 646 is that it's the monster that S&W wishes that they had never produced. When I mentioned to S&W at Shot Show that I had a problem with the gun, it was referred to as an abortion. Don't think that they ever anticipated the physics associated with the titanium cylinder in an L frame and the pressures of the 40 S&W cartridge. Once the bugs are worked out though, it is a awesome gun. Just be patient and try different loads. Well worth the science experiment. It is now one of my favorites.

Robert
 
I sent mine back for a refund. The tolerances were such that it would lock up after firing a few cylinders full of hand loads. Certain brass wasn't spaced well for the clips. Even when I used only Winchester brass the cylinder wouldn't rotate smoothly after 15-25 rounds. On the third return trip to Springfield they gave me back my money.

I DON'T think it's worth the hassle. If you reload with mixed brass and shoot a lot, get something else. I have several 625's that work just great.

Anyone tried the 610 with .40 S&W?
 
e'ville

Solved that mystery! I can now fire any reload (powder, primer, bullet or case.). It's the crimp. Reloads require almost a full turn on a Lee factory crimp die in order not to get the cases stuck in the chambers and bind up the cylinder. There are some other physics involved that create the problem, but the extra crimp seems to be the fix. Since I've been doing it, have not had a problem. Suspect that is pretty much the same problem that Mr. Walters is having, even using factory loads. Cases should drop freely with the weight of the moon clip and minimal pressure from the ejector rod. If they don't, there is a problem.

BTW this is the same problem that creates premature destruction of the 40 S&W case in a unsupported chamber of the Glock pistols. With the extra crimp I get less bulging of the case, last longer and reduce the possibility of a KBM.

Robert
 
Titanium cylinders have been made in 22LR, 32HR, 38, 357 Magnum, 41 Magnum and 45LC. Besides being rimmed cartridges, they all share something in common. A roll crimp. The 646 is the first titanium gun that uses a cartridge with a taper crimp. That is where the problem is. None of the other cartridges have experienced the problems that the 40S&W has had when used in a titanium cylinder. Took me three months to figure out that what was needed was more crimp. Even factory ammunitions benefit from more crimp in the 646PC. Don't know exactly what's going on, but I think that what the gun experiences when the cases get stuck in the chamber is a low pressure power spike. By heavily crimping the bullet, it allows the pressures to build up to optimum levels before pushing the bullet out the cylinder. My theory (Bull Sh!t) is that the bullet is somehow getting hung up and creating the pressure spike.

Robert
 
Thank you!!

Nice explaination. Thanks!

Never would have thought of this. Thought something was wrong with the moonclips. I really appreciate the insight. Thanks!
 
e'ville

Funny thing. When testing the loads, I would fire them first through the 610 and then followed by the 646 PC gun. Was starting to get worried that the 646 was going to have some kind of a catastrophic failure of one kind or another. Got a few 610s and although I love these guns, found them to be more expendable. Fired every load through the 610 and never once did it have a problem. In fact, never have had a problem with the gun, even when firing +P 10mm loads. The gun is a monster. That is what lead me to believe the the problem was with the gun (646) and not something necessarily that I was doing.

Won't say that the problem with the 646 is really a problem or a defect either. Just think that the cylinder is hyper sensitive to how the bullet is manufactured. The components have to be top notch, seat depth has to be right and the crimps have to be tight. The gun actually has made me into a better reloader.

One thing I will say about my fix is that it still not perfect. Since the crimp is going to be very tight, bullet will sometimes overshoot the chamfer in the cylinder causing a light strike. In order to achieve 100% reliability, the moon clips must be used. Does not matter which size, my fix makes the two sized clips absolete.

Robert
 
You must log in or register to reply here.
Back
Top