S&W 66-7 Two Piece barrel question

[MTKTM]

All this technical stuff is making my head ache!

I have a 66-7, bought it circa 2005 when I heard that S&W was going to discontinue the model. I'd had a couple of 19s and one 66 in the past and always liked the K platform, so picked one up. I used mine fairly extensively for a few years shooting IDPA in SSR division. I have found it to be a perfectly good, serviceable revolver, no issues or problems whatsoever. I don't shoot a lot of hot loads through it, probably never will, but I'm of the opinion that if I shoot a gun enough to wear it out, I've had a lot of fun and it's time to go get a new one!!!

 

[Gearhead Jim]

Still trying to figure out what they changed, to eliminate the relief cut on the bottom of the barrel.

Whatever it was, must not have been fully successful; or they would still be producing the 66-7 and probably some other .357 K-frames.

 

[dentkimterry]

I just looked at my newly acquired model 66-7 and it also does not have a flat spot on the bottom of the forcing cone. I bought it from the original owner who purchased it in 2005.

I went to the store already and got a box of 357 mags. Just looked at them and they are 125gr. Is it going to be wise to shoot these or should I leave them on the shelf and get some 158gr.?

 

[scooter123]

There are two things that could have been done to eliminate the flat on the barrel. One is to reduce the entire diameter of the barrel stub that extends inside the frame, the other would be to reduce the gas ring on the cylinder. I suspect that what was done is to reduce the diameter of the barrel stub to that which matches that on the J frame revolvers.

From an Engineering standpoint not having that flat will produce a slightly stronger barrel even when the diameter is reduced. The reason is that any time there is a "change in section" this creates an area where stresses will "accumulate". It called a stress riser and the effect of just a simple flat such as featured on the K frame can cause in increase in localized stresses of 5-40% depending on the depth of that flat. Personally, I think that using your 125 grain load for defense is probably somewhat safe but I certainly wouldn't guarantee that. Bottomline, I'd put that ammo up for the day you get a 686 and purchase some 158 grain loads for your model 66. Quite simply just because it's probably safe, why risk it.

 

[whoisavner]

I was shooting 125gr silvertips out of my 66-7 the other day no problem. love the gun, it shoots great, and I like it better than the 586 I used to have.

I normally shoot the 158gr magnums but some hot loads every so often won't hurt it. S&W beefed the gun up in these latter iterations, to take more magnum loads. I hardly ever fire 38s thru mine.

 

[dentkimterry]

I went to 3 guns stores today, no one had any 158gr 357's. So I got some 142gr, I thinking these should be OK until I can find some 158gr. I only bought one box of 50.

 

[71vette]

Strictly going off of what I've read, anything over 140 grain should be O.K. Also, I've got a 66-7, a 66-5, and a 66 no-dash in addition to my 19's. I'll have to get the calipers out but to my Mk1 eyeball it looks like they made the barrel stub thinner on the -7 than the -5. The -5 still has the one-piece barrel and the flat. The -7 has no flat and a two-piece. I've got a 360 with the two-piece barrel and will check the diameter of the stub against the -7.

ETA: just measured the 360 and the 66-7. The barrel stub is the same diameter.

Does the fact that the stub is J-frame sized affect a 66-7's ability to handle 357 loads?