M66-1 question

[SFT B2]

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 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)

 

[murphydog]

This was an issue with the early 580/680 series L frame .357s. The factory replaced the hammer nose (aka firing pin) and bushing under warranty, and this is likely the fix for your model 66. Personally I would send it back to the factory. Hope this is helpful.

 

[flintsghost]

Have the headspace checked. You may find it's too tight. You may also find that it binds on the barrel when the cylinder rotates during firing and dirt buildup, due to a tight barrel cylinder gap. That is common. Those have a minimum spec of .004 and a max of .10 for the period that a 66-1 was made. I don't know the headspace spec off hand but someone should have it. I would doubt that the hammer nose bushing is too large a hole unless it shows evidence of some tinkering. I have seen them too small on later guns but never too large. The too small part comes from trying to use older hammers to repair newer guns and sometimes when installing a new hammer one must use the original hammer nose due to the smaller size of the newer hammer nose bushings. You are thinking, I would guess, that primer metal is flowing back into the hammer nose on firing and causing the gun to lock up. That could happen, but in order for that to occur your loads would have to be well over what the ammunition is spec'd for and should occur regardless of the size of the hammer nose bushing. I suggest that you clean the cylinder immaculately and include the area under the extractor as this can cause the problem you have. Clean the barrel extension and then assemble and use a flat feeler gauge to check the barrel/cylinder gap. If it's at .004 or lower that could cause the same problem. I should note that my own 66-1 2.5" which is a carry piece for me has been shot a bit and it has a .004 BC gap as we speak. Considering that I used to shoot lead and changed the forcing cone angle and trued up the barrel extension, my .004 was most likely .003 or under when I got it years ago.

If you decide to send it away for repair, save some of the once fired cases as they were extracted, but 38 and 357, so that the factory can examine them. Only send in ones that were factory ammo, not reloads. Reloads not only void a warranty in some cases but are a convenient excuse to blame something that may not be at fault. Remington and Federal .357 that's +P is loaded about as hot as the guns can stand at the factory.

Repost this question in the gunsmithing category and you will probably get some more, helpful suggestions.

 

[SFT B2]

A lot of information there. Thanks! I have done some of the things you suggested. As for ammo, I have experienced it with WW Match wad cutter, various .38 and .357 factory loads so have ruled out excessive pressure. Did have a nationally known gun smith look at it but we didn't check for head space etc. Will do that. Again thanks!