I'm not a happy camper.
A few days ago a brand new M648 arrived.
Took it to the range the next day. By the FOURTH cylinder of rounds it started to misfire. By the tenth cylinder it was misfiring up to FOUR chambers per cylinder fired.
I tried multiple different brands of ammo. Didn't matter.
The strain screw was all the way tightened when I checked that.
Even on single action the misfirings occurred.
To say I was unhappy is an understatement.
Brand new gun failed on its first firing. Come on S&W you can do better than this.

Other than sending the gun back to S&W what are my options to fix this?

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N frameitis :-)

I'd check the firing pin protrusion, look for fouling/debris blocking the firing pin and/or hammer. Spritz a little oil into the action and blow it out with compressed air.

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Ain't This Fun Though?

Shooting debris under the extractor perhaps? This area needs to be free of shooting debris and lubricants in order for the casings to be supported properly. Old toothbrushes are great for removing these rimfire "leftovers".

If you determine firing pin protrusion is inadequate, there are longer aftermarket firing pins available.

Hope you get the problem sorted out.


Carter

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Ret. LE, FA Instr, S&W Armorer

What ammo were you using?

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213th FBINA

If it is brand new don't even touch it. Send it back they will send you a Fed ex label.

I agree. Send it back. Don't mess with it.

I would suspect that it isn't the gun if it successfully fired 4 cylinders of ammo then started to misfire. I would almost bet that the OP ejected the spend cases with the muzzle down and a bunch of powder debris got under the ejector star and is cushioning the rims during firing pin strikes.

The spring did not lose tension in that many cycles, the firing pin didn't get shorter, and it is unlikely that the hammer suddenly started dragging.

Clean well under the star, always eject fired cases with the muzzle up and see how it is.

Good thoughts and advice on the issue!

I wouldn't alter or replace any parts, but definitely do some cleaning and scrubbing first before dealing with warranty work.

I checked the extractor and underneath it during the firing. It was clear.
Ammo used was CCI Maxi-mag of several bullet types, Speer Gold Dot, Winchester, Hornady CD, Federal 50grn, CCI TNT 30grn, Armscor 40grn SJHP, some ancient W-W that I had on hand.
All ammo except the W-W was fresh. Each fail to fire round had an indentetion from the firing pin. It just wasn't deep enough to ignite.
Most all the rounds, when rotated in its chamber would fire on S/A mode.
Sometimes after a couple of hits.
There was only one round out of 200+ rounds that just would not fire. I tried seven different times, each time rotating the round in the chamber. I'll put that one round as a dud.(Federal).

Regardless, this is unacceptable for a brand new S&W.
My experience with S&W warranty work is not satisfactory. I will attempt to repair this myself first.

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N frameitis :-)

In that case first try removing the anvil from a spend center fire primer and placing that over the tip of strain screw to cause a bit more tension. You can get a 8-32 screw at the hardware store and make it any length you need for reliable ignition. In fact many Ace hardware stores have a selection of blue and stainless gun screws you can adjust to length with a file.

I attempted this. Would not work.
The flat mainspring, with the strain screw completely removed, lays flat against the inside face of the frame. I tried levering it outward but I couldn't get it away from the face far enough to get the primer cup in.
There isn't enough room between the flat spring and the frame.
I tried this multiple ways/times. No go. As it is I might try a thin narrow strip of shim material and try sliding it down along the inside face of the frame and then bend the outsticking tabs forward toward the open area beyond the mainspring.

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N frameitis :-)

If a shim is necessary, then something else is wrong.


Carter

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Ret. LE, FA Instr, S&W Armorer

If you have a gauge, check the trigger pull, not sure on the 648, but maybe at least 8-10 Lbs., you might check the rebound spring, it may be binding inside the housing, put a drop of Lucas Gun Oil inside, and under the spring housing, just something to try, will not hurt to call S&W, they might know the problem with that model, they will Email you a return shipping label, usually a 3-5 week turnaround, and hope you get a good gunsmith at the factory.. Good Luck..

The fired 3 cylinders full then gradually getting more and more misfires, is odd. Maybe the spring was not tempered right and flexing it cause it to quit being a spring. This would also explain why it is so straight

If the spring is still good, I still have to believe the extractor isn't seating OR the firing pin or its spring are gunked up, possibly the firing pin spring messed up.

New gun, did you clean and lube it before firing?

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Richard

Two possibilities that haven't been mentioned:

First, remove the sideplate and take out the hammer block, re-assemble, and shoot it again. There was recently a post where OP had mis-fires because the hammer block "flag" was too thick and the hammer was blocking the hammer enough to cause the problem. I have personally seen this in an N-Frame model. You could replace the hammer block or send the gun to S&W.

Second, a problem I had with a new Model 60. The first time I took it out I could not open the cylinder after firing. It worked fine before firing. When I opened it up I found a brass chip stuck between the frame and bolt, blocking the bolt from being pushed fully forward. S&W does not use any brass in their revolvers, but the chip had been in the gun when it left the factory obviously! Chip removed and everything was fine. Different problem, but could be related cause to what you were experiencing.

Note: I have been gunsmithing for over 60 years. Whenever I buy a new gun I do not worry about cleaning/lubing before firing it first. I do open up, clean and lubricate used guns before shooting them, even if everything works properly when bought

Just a thought: maybe you can tighten the strain screw all the way then use a zip tie through the grip frame to hold the spring in its arched position as you loosen the strain screw - until you can put the primer cup on the end of the strain screw and re-tighten it.

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Send lawyers, guns & money...

If the flag was too thick why would 3 cylinders full all fire and the problem slowly get worse?

The part that puzzles me is it firing fine then less and less.

The cylinders on these guns are generally pretty tight. Slight amounts of fouling can prevent a round from chambering completely which can cause the light striking condition Steelslaver mentioned. I would clean the cylinders and then polish them as well. This will also aid in extraction. If, after cleaning/polishing the gun functions properly for several rounds and then starts misfiring again, I would consider reaming the cylinder.

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So many S&W's, so few funds!!

The 648 is a 22 Magnum revolver. Were you shooting 22 Long Rifle ammunition? I do not think you can shoot 22 LR in a 22 WMR with 100% reliability.

Your right, I do not believe they make a CCI mini mag in 22WMR They do make a MAXI MAG

You would certainly end up with powder debris and possibly bits of brass everywhere firing 22lr in a 22 mag.

Notice that it has been 2 days since the OP posted last. Be nice tto hear what he figured out/

Re-read it, he does say Maxi-Mag.

Yes, but it would be easy to confuse them especial when you try them in "several bullet types"

It could cause debris to get blown in the wrong spot in short order.

If so the OP wouldn't be the first guy that did it.

All good thoughts but I still say don't mess with it, send it back. Good luck.

Sending a gun in just because it is fouled is a waste of postage and time. It isn't that hard to make sure it is clean.

But, as we have heard nothing from the OP in 3 days, I am betting the op did just that and his 648 is off and running

Been busy.
Looks like I have it figured out.
I changed out the firing pin for an "extended firing pin" from Apex.
The gun was still experiencing dead snaps on D/A. S/A it was working perfectly.
As stated before the strain screw came from the factory tightened all the way in. I thought I would try to get a shim in between the screw and the mainspring. I was going about it wrong trying to wedge something in there with the strain screw removed. Then it dawned on me to try another tack. Leaving the strain screw all the way in I placed a plastic piece between the mainspring and the frame up above the strain screw.
Then backing off the screw. The mainspring remained far enough apart for me to easily place a small brass shim where the strain screw contacts the mainspring. Then retighten the strain screw and TA DA!
It worked.
Took the gun to the range just now. Perfect operation for 50rds fired.
D/A trigger pull is stiffer than it was but not unbearable. With use it'll slick up even more.

Just for learning purposes I did try to fire 22LR round in the 648.
It would not fire any of them. It appeared the 22LR round lays too low in the firing chamber when the gun is held in the normal level firing position.
The firing pin strikes just a tad too high on the 22lr rim.
Maybe if I held the gun upside down it might fire? LOL

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N frameitis :-)

Glad to hear the shim worked. I'd be concerned with it falling out.
What most people do is take a spent primer, pry out the anvil inside then use a punch to flatten out the firing pin dimple from the inside. The empty primer cup will fit right over the unthreaded tip of the strain screw. The primer cup can't fall out, so it is a good permanent fix.

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Send lawyers, guns & money...

The Apex extended firing pin is not for use in rimfire revolvers. If it is still in the gun, remove it and put the factory pin back in place. Otherwise, you risk damaging the cylinder.

From the Apex web page: Not for use in rimfire model revolvers.

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So many S&W's, so few funds!!

Go to ACE hardware many of them have an assortment of gun screws. Get an 8-32 screw with the correct head. It will be to long, but you can grind or file it to the length of your original screw plus the thickness of the shim.
If you get a couple 8-32 nuts and tighten those on the screw you will have something to hold it in a vise with while filing and when you remove them they will remove any burr from last thread.