Model 66 locking up

[Wags]

I currently own a Taurus .357 (model 66) and had an odd problem occur while at the range last week.  I shot a box of UMC 125 gr. rounds for the first time, and had the gun completely lock up on me three times.  Up to this weekend I only shot American Eagle 158's through it without any problem what so ever.  When the pistol locked up, the cylinder, hammer, and the trigger would not budge.  With some slight coaxing, a little wiggling of the cylinder, and every bad word I could think of I was able to unjam the pistol each time.  Has this happened to anyone else or is this unique to me.  I'm thinking it was the UMC bullets, but not sure.  I'll probably take it to a gunsmith, but was curious to that all you "in the know" shooters thought about this.  Any ideas would be greatly appreciated!

[jhm]

Wags:  It sounds like your problem might be the ammo, if the bullets are walking forward due to recoil they will lock up most revolvers, take it to the range again if you have any ammo left and after you fire a couple of rounds open the action and measure them to see if they are walking forward.   JIM

[Wags]

Jim, thanks for your opinion, that's what I'm hoping is the problem.  I shot all the UMC I had, all I have left is American Eagle, and one box of winchester 110's, so I'll give either of those a try.

[John Traveler]

Wags,

If the problem is NOT bullets "walking out" of cartridge cases during recoil, the problem is usually easy to diagnose:

Some ammo burns a lot dirtier than others, and the firing residue can inhibit cylinder rotation if the barrel-to-cylinder gap is too small.

The cyclinder lockup you described was a big enough problem during the 1970's late M19/early M66 production that S&W made some engineering and production changes, including modifying the cylinder "gas ring" clearance.  The revolvers would frequently lock up with extended or rapid fire using hot loads.

Look at your cylinder face and see if there are scuff marks where it drags on the barrel forcing cone.  Use a feeler gage to measure the cylinder gap.  It should be a uniform 0.005 to 0.006" inch.  If it is too tight, the cylinder will sometimes turn hard when the gun is fired.  If too tight, have your gunsmith regulate the cylinder gap.

[Wags]

Thanks for the info, I plan on checking out everyone's suggestions.  I really enjoy shooting it, and my brother, and father shoot also, and they haven't had this problem, dad shoots a ruger, and my bro shoots a S&W, and he uses UMC without any problems at all..