I don't know that my answer will be of much use to you but here's my experience.
Bought mine in Aug of 2018. Have shot about 1,500 rounds predominantly 165gr SWGC over 13.1gr A2400 for about 1,100 fps.
No problems except that cylinder starts to get harder to turn with 50 rounds plus. This due to powder and lube fouling from the cast bullet load and powder charge. It is easy to cure with a drop or two of any oil or penetrant - I use both CLP & Synthetic transmission fluid.
Thank you very much for your information, I see that the model 66-8 is a verey sturdy gun, and also accurate enough for me!!!, but as you say due to the cost of the Smiths in my Country
My understanding is that all "endurance package" improvements are designed into the the revolver. The redesigned yoke allows the barrel shank to be full size beefing up this area.
Here are some 25yd groups I shot early on with mine. These were shot rested on my range bag or stacked carpet squares.
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Keep in mind I'm in my early 70s and eyesight is a bit challenged and I'm not the best shot. So, my guess is that my gun is capable of at least 4" groups at 50 yds. Our range has a 10" plate at 70 yds which I can consistently hit off hand.
Here are some chronograph results:
2 Ύ M66-8 chrono results from my then new LabRadar chrono
For Information Only, Use at Your Own Risk
Labradar Muzzle Velocity (familiarization run)
60 Deg F
S&W M66-8 2.75" .357 Mag
130gr Fed Hydra-Shok JHP "Personal Defense" PD357HS2 H
.. 1,416 fps avg (84 fps ES) -- two rounds
140gr Underwood Xtreme Penetrator (Philips head mono metal).. 1,422 fps avg ( 5 fps ES) -- two rounds
158gr Horn Xtp - 15.0gr A2400 Std small pistol, new Starline...
1,316 fps avg (49 fps ES) -- six rounds
180gr Buff Bore
.. 1,312 fps avg ( 6 fps ES) -- two rounds
185gr LFNGC (Beartooth), 15.0gr Lil'Gun, CCI 400 New Starline.. 1,228 fps avg (14 fps ES) two rounds
200gr WLNGC (leadheads), 13.4gr H110, Fed 205, New Starline.. 1,102 fps avg ( 4 fps ES) two rounds
200gr WLNGC (leadheads), 14.4gr H110, Fed 205, New Starline.. 1,155 fps avg ( 2 fps ES) two rounds
(purported to be the Doubletap load info)
200gr WLNGC (leadheads) handload with Lil Gun
. 1,266 fps avg ( 2 fps ES) -- two rounds
Load data not given -- maybe too much of a good thing. Spent cases fell from chambers, and no obvious signs of over pressure. Recoil was heavy. Don't even know if this stabilizes.
If even needed, I would limit useage of the 180, 185, and 200gr loads in J & K Frame guns.
Some very knowledgeable people don't think the M19/66 wil stand up to long term useage of full house .357 magnums. This is based on legacy models, not the current 66-8 -- for which I believe the jury is still out.
With your situation (cost and repair and warranty situation), I might be incline to go the 2 3/4" L Frame M686.
For what its worth.
Paul