Hot loads for 66-8

[Model5]

I’m curious what would be the hottest load you would run over a prolonged period through a new model 66-8? I have a large amount of 125gr jacketed soft points. My current load for them is 18.9gr of w296 with cci magnum primers. The velocity is running right at 1400fps which is what the handbook has listed for that load but with a 6” barrel (mine is 4”). 20.3 grains is the max listed in the handbook. I’m just curious if prolonged firing of these will be detrimental to my firearm, or am I just overthinking it.

 

[Ivan the Butcher]

Why would you want to "Hot Rod" a K-frame?

Problems with that is what inspired the L-frame (which I have a 4") But my beast loads always went in the 4" 28-2.

I had companion loads for the M-92 & Marlin 1894 and the 686 and 28-2. I often prefered them in the handguns to the carbines.

Ivan

 

[max]

Hot 125's are thought to be responsible for cracked forcing cones on K frames, I sure wouldn't shoot it in any of mine.

 

[LoboGunLeather]

Your Model 66-8 is the modern incarnation of the original Military & Police revolver of late 1890s vintage. Steel alloys have improved somewhat and modern manufacturing methods have evolved to a higher state, but essentially you are dealing with a platform originally designed and intended for much lower pressure loads (.38 S&W, .32-20, and black powder level loadings in the original .38 Special).

.357 magnum chambering in the medium frame S&W (now known as the K-frame) was added much later, adapting a cartridge originally designed for the large-frame (N-frame) magnum revolvers to a more compact piece.

Since its introduction as the Combat Magnum (later known as the Model 19) there have been many commentaries about the wisdom of regular use of magnum ammunition in the K-frame revolvers. 60-plus years of experience have led to a general consensus that occasional use of .357 magnum ammunition is probably acceptable, but regular use of such high pressure ammunition should be avoided.

I have owned and used Model 19 and Model 66 revolvers for about 50 years. I consider them to be very well suited for regular use with .38 Special and +P level ammunition, but not sufficient for a steady diet of factory-level pressures of .357 magnum. In my opinion, subjecting a K-frame revolver to magnum ammunition on a regular basis is an invitation to premature wear, at best, or catastrophic failure at worst.

 

[colt_saa]

I’m curious what would be the hottest load you would run over a prolonged period through a new model 66-8? I have a large amount of 125gr jacketed soft points. My current load for them is 18.9gr of w296 with cci magnum primers. The velocity is running right at 1400fps which is what the handbook has listed for that load but with a 6” barrel (mine is 4”). 20.3 grains is the max listed in the handbook. I’m just curious if prolonged firing of these will be detrimental to my firearm, or am I just overthinking it.

There is no SAAMI spec load that is unsafe in your Model 66. Certainly none that that should lead you to worry about catastrophic failure of your 357 Magnum firearm.

I would not recommend that you exceed (Hot Rod) SAAMI specifications for any firearm's cartridge

The -8 engineering revision of the Model 66 brings new metallurgy and manufacturing techniques to the K-frame that are significant improvements over what could be manufactured over 60 years ago when the K-Magnums first came on the scene

As you are already aware, your hand load is on the low side for that powder/projectile combination

Over the last 40+ years I have hand loaded and fired just in excess of 8000 of the Winchester 125 JHPs with a somewhat larger charge of H110 for my snub nosed Model 19/66 revolvers and the rest of my 357 Magnum family with all of those loads within SAAMI spec. Heck my 125JHP load gets 1243 FPS out of the 2 1/8" Model 640s. Many tens of thousands of rounds of various other hand loads and Factory ammunition has additionally gone through my firearms over the decades. I still have a large amount of the Winchester 125s on hand to load and I plan on enjoying them

It is a shame when we let the shortcomings of 1970s manufacturing hold us back from what is achievable half a century later in the 2020s

It is kind of like driving our modern cars at under 30 miles per hour because that was what the tires that came out 100 years ago were designed for

Every time that metallurgy, manufacturing or design improved . . . . Smith & Wesson incorporated those improvements into their products. How else could we have gotten to J-Magnums in 1996 ?

 

[Nevada Ed]

The new S&W 66-8 is a great weapon but with the heavy 15 pound trigger
it is 10 seconds slower in shooting all rounds vs the lighter trigger on the M66-6.

However the new design has not removed any metal from the bottom of the barrel,
like they did with the M19's, which makes this revolver a lot safer
with the use of full load 125 gr JHP.

If I had to use full loads in this revolver, I would move to the 140 gr XTP
that would be a little easier on the weapon......
and receive better accuracy, at least in my revolvers.

Load up some hot 110, 125 and 140's and see what happens.
I was a speed freak when I first started loading but learned that full loads
usually were saved for hunting loads and I backed off the powder for my target loads.

Have fun.

 

[Model5]

There is no SAAMI spec load that is unsafe in your Model 66. Certainly none that that should lead you to worry about catastrophic failure of your 357 Magnum firearm.

I would not recommend that you exceed (Hot Rod) SAAMI specifications for any firearm's cartridge

The -8 engineering revision of the Model 66 brings new metallurgy and manufacturing techniques to the K-frame that are significant improvements over what could be manufactured over 60 years ago when the K-Magnums first came on the scene

As you are already aware, your hand load is on the low side for that powder/projectile combination

Over the last 40+ years I have hand loaded and fired just in excess of 8000 of the Winchester 125 JHPs with a somewhat larger charge of H110 for my snub nosed Model 19/66 revolvers and the rest of my 357 Magnum family with all of those loads within SAAMI spec. Heck my 125JHP load gets 1243 FPS out of the 2 1/8" Model 640s. Many tens of thousands of rounds of various other hand loads and Factory ammunition has additionally gone through my firearms over the decades. I still have a large amount of the Winchester 125s on hand to load and I plan on enjoying them

It is a shame when we let the shortcomings of 1970s manufacturing hold us back from what is achievable half a century later in the 2020s

It is kind of like driving our modern cars at under 30 miles per hour because that was what the tires that came out 100 years ago were designed for

Every time that metallurgy, manufacturing or design improved . . . . Smith & Wesson incorporated those improvements into their products. How else could we have gotten to J-Magnums in 1996 ?

Thanks for your input. I ended up going alittle crazy when I first started reloading for my 66 and was able to snag about 2k 125grain bullets for a very good price. It wasn’t until afterwards looking for data I came across all the horror story’s of flame cutting the top strap and cracked forcing cones attributed to 125gr bullets. But with most online firearm lore I took it with a grain of salt. It always seems the majority of the time the input you come across are the horror stories of mishaps and such but none with first hand experience.

My biggest concern with regards to my situation was the fact I’m seeing 1400fps with 2” shorter barrel then the test gun the handbook lists. I wasn’t sure if that was cause for concern or not.

 

[BLUEDOT37]

The revised M66-8 is a lot stronger than it's predecessor.

As stated, the load you mentioned is a reduced load, & while W296/H110 isn't my favorite magnum powder in my 357s, that's also a plus.

The new forcing cone design on the 66-8 is far better than the old design.

Of course, as to be expected, hot loads will be harder than mild loads on any revolver.

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[Greyman50]

Question, why shoot max or close to max loads continuously from a K frame? Saw a M-66 at swap meet this spring that had Obviously fired way to many hot loads. Forcing cone looked like someone had used a dremel tool with cut off disk to cut slots in it. Years of experience has been posted above regarding hot loads in K frames. Obtain a N frame if you insist on shooting hot loads all the time. Sell or trade up.

 

[stansdds]

The Model 66-8 is the current production version and does address the short comings of the prior versions of the K-frame when chambered in 357 Magnum. It is quite a bit stronger than the older K-frames and the barrel's forcing cone is far less likely to develop a crack. The Models 19-9 and 66-8 should be able to withstand thousands of rounds of full power 357 Magnum ammo. I certainly would not use hot-rodded reloads that exceed published data that is known to be within SAAMI safe pressure levels.

Getting the most velocity out of the 357 Magnum with any full power ammo will require a barrel longer than 4 inches. S&W developed the 357 Magnum cartridge and the Model 27 revolver with an 8 3/8 inch barrel. They did not use this length of barrel because it made the Model 27 look pretty. To see some effects of barrel length and velocity, check out a website called Ballistics by the Inch. Here is a link to their site, interesting reading.
BBTI - Ballistics by the Inch :: Home

 

[Cdog]

Any modern firearm with the .357 Magnum designation should withstand a constant diet of magnum loads.

I have a $300 plastic Taurus 605 that's never chambered a non magnum round. It seems to be just fine. The revolver has withstood the punishment better than my right hand.

 

[murphydog]

I think it depends on your motivation for putting (near) full power loads through it?

Yes, as noted above it will take many SAAMI spec loads before shooting loose, but if your primary purpose is shooting targets lower powered loads (with the occasional full load mixed in) will be easier on you and the gun. Kind of like not driving your powerful sports sedan at 9/10s just to get to the grocery store.

Good luck in your decision.

 

[shocker]

Blast away with your 66-8. Even if you erode the forcing cone, swapping a barrel liner is an easy job.
As has been pointed out, the weak points of the old designs were engineered out of the new one. Smith says they are strong as the L-frames.
I shoot 125 gr bullets exclusively. I have the short barrel so I use a faster powder (AA5) at maximum loading.

 

[Model5]

Question, why shoot max or close to max loads continuously from a K frame? Saw a M-66 at swap meet this spring that had Obviously fired way to many hot loads. Forcing cone looked like someone had used a dremel tool with cut off disk to cut slots in it. Years of experience has been posted above regarding hot loads in K frames. Obtain a N frame if you insist on shooting hot loads all the time. Sell or trade up.

To be honest, I never set out to just run max loads through it. What I found all over the internet about not reducing loads with H110/W296 had me concerned because your hand will blow off and this and that. I figured running at the middle of the handbooks data would be a happy medium for my first loads. And it seemed accurate enough and isn’t miserable on your hand. I eventually got around to getting a chronograph to be on the safe side and I was surprised when my velocity was hitting right at what the handbook stated with 2” less barrel. I guess my real question should be is how much velocity is lost or gain from 2”. Or is it too little to pick up a discernible difference until you get to the 8” and up range.

The other thing I didn’t realize is the complete aversion everyone apparently has to firing 357 magnum out of their 357 magnum. I’m very confused by this.

 

[shocker]

I was surprised when my velocity was hitting right at what the handbook stated with 2” less barrel. I guess my real question should be is how much velocity is lost or gain from 2”. Or is it too little to pick up a discernible difference until you get to the 8” and up range.

The other thing I didn’t realize is the complete aversion everyone apparently has to firing 357 magnum out of their 357 magnum. I’m very confused by this.

Do you trust your chronograph? If so....
Congratulations, you have a "fast" gun. Enjoy.

 

[Model5]

Do you trust your chronograph? If so....
Congratulations, you have a "fast" gun. Enjoy.

Between the 357 yielding near perfect results and my M1 carbine slinging my loads for that right at it’s expected velocities. I would say that I trust it to be reasonably accurate.

 

[alwslate]

From my own chronograph tests with 125 JHPs and 296 out of a 4” mod 28-2 if you’re actually getting 1400 FPS out of your gun and loads I’d also say you have a very fast gun.

 

[Nevada Ed]

I saw a M19-4 killed by using tons of Factory full load 110 & 125 JHP back
in the 1970's , to the late 199o's.
A crack at the bottom of the barrel finally showed up.

I would use +P 357 light bullets less than most speed freaks........
and treat my M19 as a light weight .357 Magnum revolver made for heavier &
slower bullets , that are easier on the weapon, for it to last a long time.

The 66-8 is almost a "L" frame ...........
I just don't think that todays full ammo, is any thing like the ammo made back in the 70's, with the light 110 & 125 JHP ammo.
The last 110 JHP ammo that I saw, was waterd down, a lot.

 

[rockquarry]

I started loading the .357 Magnum cartridge in a variety of revolvers about fifty years ago. Most loads have been with cast bullets but I tried lightweight jacketed bullets as well with heavy charges of slow burning powder. I saw no advantage to these light bullets but all our needs are different so they likely have some usefulness with some shooters.

My concern with such loads would be more rapid bore wear just ahead of the forcing cone as well as in the forcing cone itself. However, if you find light bullet high velocity loads are more accurate than other combinations, they might be good loads to stick with, particularly if you don't shoot a lot. Bore life would be worth sacrificing for excellent accuracy.

 

[Nevada Ed]

Back in my younger days, I did not have use of a chrony and just bought any ammo I could find
and send it down range at paper, jack rabbits and other things of interrest.

With a 2014 chrony I started to see what my ammo was finally doing.
Midway had some data on it's 110 & 125 JHP and that was all over the place.
They only had two 110 gr jhp loads and they both stated a watered down 1295fps.
However, the 125gr was still healty with a few at 1450 fps ..... (no barrel lengths)

In my early years I only had Blue Dot for my full loads.
About ten years ago I finally bought my first pound of 2400 powder.
I have never used the H110 type powders in my 357 revolvers, yet.

I do agree with this 1450fps out of a 6" barrel, since I did reach this high fps in one box of ammo, with my newer M686.........
but find my rem/w-w jhp bullets a lot more enjoyable at 1220fps.

PS;
a note on recoil in my 686 6" 2.5 lb revolver;
125 jhp 1448fps.................. R 7.07 ft/lbs

158 jhp 1430fps................. R 11.45 ft/lbs

Feel lucky ?