I'm having a difficult time getting my reloads to function in my 646. The funny thing is they work fine in my XDM and my STI (if anything I thought it would be the other way around). It's as if they are too long, the cylinder can't be swung closed. As a comparison, factory ammo drops in nicely.
I'm very much a noob so if my error is a stupid one I won't be offended.

Thanks,

Mike

It sounds more like a cartridge OAL (overall length, than a case resizing issue)

What bullet are you using and what is you OAL of a loaded round.

Does this happen when you first load the gun or after you fire a shot or two and then the cylinder does not open? If that happens your crimp is to light.

__________________
Still Running Against the Wind

Where is it interfering, at the barrel because the bullet extends from the front of the cylinder? If this is the situation (I doubt it) then seat the bullets deeper.

Look at the head of the cartridges, is the primer flush, below flush, or does it stand slightly above the case head? If it is high, seat the primers deeper.

If the primers are flush or below, watch as you close the cylinder to see if the case heads are interfering with the breech face. If they are then try some cartridges in the cylinder without the moon clips. If there is still interference with the breech face you need to trim your brass.

If there is interference with the clips and none without them either the clips are too thick and you need to try another brand, or the back of the cylinder is too long and there isn't enough clearance between the cylinder and breech face for both the case rim and the moon clip. If this is the situation send it home for a tune-up under warranty, be sure to thoroughly describe what is happening throughly.

It has to be one of these, figure it out.

__________________
Gunsmithing since 1961

The rim of the case hits the breech face.


This is exactly what is happening.

But these rounds work fine in my autos.

I'll pull some bullets and measure the cases.

What about build-up in the chambers?

Check the thickness of your moonclips. My 646 was shipped with .035 and .042 moonclips. 40 brass is very notorious for having different rim thicknesses from different manufacturers. Check the stamp and separate to see what works. I run reloads exclusively through my 646 with no issues. This is absolutely my favorite handgun to shoot. Good Luck!!

I thought of that. I can't get it to close with no clip. The length of the cases seem fine too.

Hmmmm, it sounds like your 646 may have to be checked out by a competent gunsmith. My gun will not even fire without the use of moonclips. The 646 was designed for moonclip only use, you cannot even eject shells w/out a moonclip. Maybe post a few pics for one of the more knowledgeable members to take a look at??

I think you shoud post some clear photos of both your loaded ammo and the interference when loaded in the gun. Without photos it is virtually impossible to diagnose. HJowever I suspect it is ammo related. Pertinent dimensions of your ammo would be helpful. An easy method for determining if it is an ammo problem is to see if factory loaded rounds exhibit the same problems.

I said in my original post that factory ammo works fine. There is no doubt in my mind that this is due to my reloads.
Now if I can just figure out what the heck is going on....

Measure the factory ammo at all the important spots then compare the measurements to your reloads and you will find the problem.

__________________
Freedom is never free!!
SWCA #3437

This happened to me when I first started loading for my 625. The majority of my rounds would not fit in a Dillon case gauge. I increased the crimp until I was at .469 or so and now they all work fine.

There should be no need to trim the brass.

Looks like an OAL issue. I tend to load a little long (1.15-1.17) because they feed a bit more reliably in my STI and I think it tames them a little too.

It looks like the style of bullet could be an issue also, where the "curve/hip" starts appears to be the key.

The two autos that I shoot will handle an OAL of 1.2, I expected that the revolver would be more forgiving but that's not the case. I'll just use up the long reloads in the autos and start seating a little more going forward.

My 646 loads and fires anything that will fit in a .40 S&W case gauge, an item I highly recommend for reloaders.

__________________
Science plus Art

MWark,

You diagnosed the dimensional interference in your last reply. As I read through your thread I kept expecting the next comments to be about what you described as your selection of OAL positioning the "hip" of the bullet too far out of the case. It sounds like the bullet diameter is too large to enter the chamber throats. Inside auto pistol and rifle barrels the area just ahead of the case neck is called the ball seat and is cut to a dimension that accepts a short length of the bullet's full diameter cylindrical shank. Your pistols' ball seats are larger than your 646's throats. Oversize throats are the most common cause of difficulty getting revolvers to shoot accurately so I would not complain to S&W about tight throats. It's common for loads developed for one or two of our guns to not work out in the others. While you probably will come up with a load that works acceptably in all your handguns, usually the best accuracy is obtained by tailoring loads to individual guns.

Other mention the bullet profile. Try pushing a new bullet throught the throats, if it does not pass freely either seat deeper or the throats can be slightly enlarged by polishing until they pass with slight resistance. You can also slug the throats and nic. the slugs and bullets. The throat slugs should be as large as your bullets or slightly (.001) larger for jacketed bullets.

If your bullets mic. .401 then try some that are .400, both sizes are available. Same way, check to see if they pass the throats without excessive resistance.

I guess what I should have told you first was to check for function starting with a sized but un-expanded case trimmed to SAAMI maximum length. If the gun works with just the case (eliminates charge hole build-up) then start adding, in this order: primer, moon clip, bullet. At some point you will find at which change the problem evidences itself, and then you will know which step needs to be revised.

If the head of the sized, trimmed case contacts the breech face then you have already discovered the problem, the gun needs to back to S&W to have the charge holes revised to provide adequate headspace.

__________________
Gunsmithing since 1961

If memory serves, there are also 2 different thickness's in .40 moon clips.

The cases may need to be roll sized after being fired in a semi-auto. Does re-loaded ammo that was only fired in your revolver work?

I've got it going good now. It was an OAL issue, I need to keep them under 1.16. You wouldn't believe how fun that gun is to shoot. Thanks for all the responses.

There is a echo in here!

Occam's Razor

__________________
Still Running Against the Wind