Got a S&W M65 Stainless .357 Magnum, now some questions.

Laz, well, I'm not a metallurgist, and I don't play one on TV...
But, what I have seen in damaged guns, and in talking to many folks about .357s in K-frames, it seems the consesus is that it is the speed of the slug smacking into the forcing cone more than it is the weight.
Also, in comparing one load to another, keeping Force=mass x velocity x velocity in mind, a load that's a little lighter and a little faster can pack more punch than a load that's a fair amount heavier and a tad slower, or even the same speed.

Now that we're all thoroughly confused...
The muzzle velocity, which of course is the speed of the bullet upon exiting the muzzle, gives us zero clue as to what the impact velocity of the bullet upon the forcing cone is.
A lighter bullet, like the 125's and 110's get started quicker, as they are lighter and have less inertia keeping them at 0 fps.

So, just picking some numbers out of the sky,
a 158gr JHP might be smacking the forcing cone at 600 fps
a 125gr JHP might be smacking the forcing cone at 800 fps
and
a 110gr JHP might be smacking the forcing cone at 1000 fps.

Like I said, I'm sure those numbers are not right, I just picked 'em, but I would bet a paycheck that the lighter bullets are hitting the cone faster than the heavy bullets, even in loads where the muzzle velocities are equal or even higher in the heavy bullets.

It would be very interesting to me if some ammo manufacturer, or anyone for that matter, did research on the impact speeds on forcing cones in relation to the other variables.
I don't even know how that could be measured.

Bottom line, the faster a bullet hits the forcing cone, the more wear it will suffer.

$.02, -Kframe :)
 
K-frame - Thanks for the reply. I see what you're saying and understand the logic. Some points are still problematic for me, however. A 110 grain .357 loaded to most manufacturers' specs (approx 1300 fps, 4-V barrel) is roughly equivalent to a 9mm 115 grain plus P and from a snubby barrel probably roughly equivalent to a good standard pressure 9mm, i.e. 1100 to 1150 fps. Granted there have not been that many 9mm revolvers, but I've seldom heard of them having this problem. Again, a 1500+ fps 110 grain load, I can understand would be a real blowtorch in the forcing cone but the "normal" 110s are relatively mild, roughly equivalent energy-wise to the Remington medium velocity 125 grain Golden Sabers which are particularly recommended for snubbies. Speaking of blowtorches, I am sure I have read that Dick Metcalf has maintained that it is the hot gases and powder particles driven to high speed that act as a cutting torch on the forcing cone. If that is the case, again, the very high speed light bullets might well be worse than the heavier ones, but I still don't understand the modest velocities of the 110 grain loads being in the same ballpark as the fire-breathing full velocity 125s. I ain't claiming they're not. I'm just getting my brain tied in a knot trying to understand why it would be so. BTW, I favor Winchester white box 110s for my SP101. Overall, I like 158 grain loads the best, or 145 Silvertips, but, frankly, I find them much harder to shoot well from the SP than the lighter loads. My GP-100 and Model 28 are another story and there the heavier bullets rule, for me at least. I don't use full-bore 125s much at all.
 
Laz,
...but I still don't understand the modest velocities of the 110 grain loads being in the same ballpark as the fire-breathing full velocity 125s.
Click to expand...

I think it comes down to the velocity at the forcing cone, as opposed to muzzle velocity.
The lighter the bullet, the closer it will be to its muzzle velocity when it is at the forcing cone than a heavy bullet.

What's a good analogy...
OK, a V-8 powered Bentley weighing 5500 pounds tops out at 170mph (according to the ad I saw).
A Kawasaki crotch-rocket weighing roughly 500 pounds also tops out in that range (probably faster, I dunno).

So, if you put them side to side and had them both 'floor it' at the same instant, I would much rather be standing ten feet in front of the Bentley, than ten feet in front of the bike.
The bike at one second is going to be closer to its ten second speed then the Bentley will be to its ten second speed.

I don't know if that clears it up at all.

As far as Metcalf's opinion that the forcing cone is "gas cut", I dunno.
The cones I've seen have been cracked, not cut. The crack is always at the bottom of the barrel, where it is flat on the bottom and thinnest.
I do wonder if it is mainly that the area is thin, or whether the fact that it is flat and the rest is concentric somehow concentrates the stresses at that point that causes the crack.
Supposing that a barrel that is uniform and thin may hold up better than one that is thicker all around but has one flat area.
Like, the J-frame magnums. Very thin at the forcing cone, but apparently able to handle the fullhouse mags in torture tests.

Hmmm, -Kframe :)
 
I checked with some ammo makers on this, because S&W K-frame .357's are among my favorite guns.

They confirmed what Metcalf said about erosion, calling the unburned/still burning powder, "ejecta". Said it contributes to erosion and gas cutting of the top strap.

I don't know if this is what cracks barrels at the bottom of the forcing cone, but something seems to in some guns, so I avoid hot 125 grain .357 loads in K-frames!

Overall, I have decided that the 158 grain Hydra-Shok will probably expand enough to work on human targets and penetrate better and hold together better than lighter bullets. And it will do a better job on large animals, if I ever have to shoot a Doberman or a bear.

Lone Star
 
LOL, well, two things are reasonably clear to me. My SP101 is probably up to the task of firing as many 110 grain bullets as I am likely to run through it. Second, I really need to get better at handling 158 grain loads through the wee beastie. These days, my K-frames are .38s and they are keepers.
 
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