Md-66-1 cylinder locking up

[SFT B2]

I posted this in the general revolver forum a few days ago and one member suggested reposting in this section. Got several replies

In my past as a LEO, had a three M-19s for duty. Gave one to my brother for graduation from dental school. bought a M-66 2 1/2" when in the detective bureau and traded it off when we went to autos. Regret getting rid of any of them.

I've been looking for a real clean M-19 for about 6 years and finally ran across a very nice M-66-1 in a box. Grabbed it at $600. Very clean, looks new.

With some ammo it will lock up, hammer won't cock, cylinder won't open. Forced the cylinder open checked the brass and noted most had some degree of primer cratering thus locking the thing up. Occurs with a variety of commercial and hand loads, both Mag and .38 SPC

Looking for a fix. Send to S&W? Thinking the firing pin hole is too big.

Thanks

Steve (SFT B2)

 

[Geno44]

Are the cylinder bores and forcing cone area immaculately clean and free of carbon and lead?

 

[pmosley]

I suspect ejector rod has backed out to some degree


Sent from my iPhone using Tapatalk

 

[StakeOut]

You might want to take the side plate off to see if the cylinder stop and the cylinder stop spring are moving.

The bolt,aka cylinder catch,also has a lot to do with locking up the cylinder.

If it were me I'd strip it down and check the parts,especially those that have a spring that's needed for operation.

https://www.gunpartscorp.com/Manufa...6/KFrameRevolvers-38382/66-1-36833.htm?page=1

 

[armorer951]

Sending the gun back to the factory for an evaluation would certainly be an option. You said the gun locks up with "some ammo". Are you talking about factory .357 caliber ammunition, or handloads? The primers, or overcharged loads could also be possible cause of the issue.

If you determine that ammunition is not the cause, then I would take a look at several things in an attempt to diagnose the problem. First, since this is a "used" revolver, I would check the condition of the internals with regard to alterations involving the mainspring, mainspring strain screw, or other components.....any evidence of alterations or modifications?

Another thing to check is the integrity of the hammer nose bushing and the hammer nose. Is the hammer nose spring loaded? Is it moving freely in the hammer? Does the hole in the bushing look damaged, or oversized? Does it look worn? Any evidence of peening around the hole? Your K-series hammer nose end diameter should be around .080" with a corresponding diameter hole in the bushing.

Another thing to check would be the rear gage on the cylinder (head space). For counterbored cylinders (recessed) ....this should be between .012" - .018", measured with a feeler gauge inserted between the rear of the cylinder face and the breechface.

 

[SFT B2]

Thanks for the info. Regarding ammo, a variety of ammo both .357 handloads and commercial and .38 Spc commercial experienced the problem. Shot 24 rounds of .357, 6 were handloads I use in my 582 and M-27 and 12 W-W Silver Tip and 6 Federa lwere used and have fired less than 100 of the .38 Spc all commercial stuff.

I'll have respected local gun smiths check out the other things you mentioned. Identifying the issue will hopefully lead to a fix!

 

[Geno44]

Please keep us posted on what the solution was.

 

[SFT B2]

M-66-1 cylinder locking up

Roger, will do. Plan is to take it out to the range and do a detailed log of the cartridges and which chamber each was loaded and fired in. Also will have my smith check headspace, etc prior to.

 

[SFT B2]

M-66-1 cylinder locking up

HMMM? Thank you all for the info, I'll keep it for possible future reference.

NOW, I just got back from the range. Sunny, 60 degree NW wind at 15mph. Took a variety of rounds, mag and spc. Took a note book cataloged rounds and chambers. After 40 rounds....Nothing! It worked perfectly. I almost always clean after each use. I'm going to leave it alone, gather some more varieties of ammo and try it again, then again to see if it replicates the issue in my previous 4 outings.

Again, thanks to all who offered advice! Today it is a great gun!

Steve, SFT B2