stonebuster
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Does shooting a steady diet of 357mag 158 grain FMJ and 38 special FMJ 130 grain wear the forcing cone more than unjacketed ammo over thousands of rounds?
357mag FMJ and forcing cone
- Thread starter stonebuster
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It's the 110 and 125 gr bullets that are hard on the cone. Because they are light they hit the cone with a lot of force. This was a problem for the S&W K frame .357 revolvers more then anything. For that reason I tend to stay with 140 gr or greater in weight.
buck460XVR
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The problem with the light for caliber bullets with full house .357 powder charges is not the force of the bullet hitting the forcing cone, but the amount of hot gases and carbonized unburnt particles going by the bullet as it enters the forcing cone. This is the main cause of top strap erosion too, not the bullet bouncing off the top strap before it enters the forcing cone............
Light for caliber bullets have a shorter profile, thus allowing more of the hot gases and unburnt particles to get past the bullet as it goes thru the cylinder gap and not follow it directly into the barrel.
Light for caliber bullets have a shorter profile, thus allowing more of the hot gases and unburnt particles to get past the bullet as it goes thru the cylinder gap and not follow it directly into the barrel.
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stonebuster
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So does it follow that 38 specials shot out of a 357 mag will wear the forcing cone more than 357's due to it's shorter profile? I assume shorter profile means length.
KevininPa
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A 158 grain .38 special bullet is the same length as a .357 158 grain bullet. It's the bullets that are smaller than 140 grain that cause the damage. It's the .357 cases that are longer for more powder.
I understand 110 grain .357s loaded to a nominal velocity of 1500+ FPS from a 4 inch barrel being hard on forcing cones. But most current 110 grain .357s are loaded to nmt 1295 FPS from the same barrel; roughly like a 9mm plus P (which is even shorter, yet we don’t hear about 9mm revolvers having the same problem). It doesn’t compute for me.
buck460XVR
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Most 9mm ammo, uses fast burning powders, while hot .357 loads use slow burning powders, which are the one's most likely to promote forcing cone erosion. Pretty simple computation.
Full power 357 magnum loads use a LOT of powder. A 158 grain bullet eill use 14-17 grains of slower burning powder. A 125 grain bullet will use 18-22 grains of the same powder. If you were to used the same powder commonly used in a 9mm to liad magnums you would only be able to load 7 or 8 grains of powder and wont reach the full Velocity you can get from slow powder. Which causes more erosion? A lot of slow powder or a little fast powder? BTW the same powder that you would use 7 or 8 grains of for a 357, you would only use 4.5 to maybe 5.5 grains of in 9mm
Most decent quality guns have a forcing cone that will withstand many thousands of rounds before causing significant damage. What Buck460xvr said is accurate. It's the full power .357 loads with light bullets, 110 and 125gr, that seem to be the worst. Unless you are shooting max .357 loads constantly I wouldn't worry much about it. With .38 loads you will probably wear out before your gun does.
Which is what prompted my initial comment. Corbon 110 grain .357 is spec’d at 1500 FPS but most of the major brands of 110 grain .357 are spec’d at 1295 FPS. Full power 125s are spec'd at 1450 FPS and Remington medium velocity 125s are spec’d at 1220 FPS. If 110 at 1500 is full power (and I think it is) what should we call 1295? I would call that medium power and wonder if it would be anywhere near as hard on forcing cones. I think probably not. Most threads on this subject are unclear, at best.
buck460XVR
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The real issues with hot .357 loads and forcing cones came about when guns originally chambered and designed for .38 special were chambered for .357 when it came out, i.e. older S&W K-Frames. These guns had thin forcing cones and a flat at the bottom where the cone was thin. The lower part of the forcing cone on the K frame .357s is machined to clear the gas ring as the yoke/crane closes.They stood up to .38s just fine, but full power .357s, not so much. Again.....The issue with the shorter (lighter 110/125 gr) bullets is they, the bullet's base, leaves the brass case before the meplat engages the forcing cone and the expanding gas can actually stream around and beat the bullet to the cone. This same gas is responsible for topstrap flame cutting. This is generally not a problem with newer production models intended for .357 like S&Ws L-Frames and some of the newer K-Frames.
25-20 WCF
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Yes, the lightweight bullets are more prone to bounce off the top strap causing undue wear....see post #4.
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AZAndy
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That's a really peculiar revolver you have there. If it were mine, I'd get rid of it.
buck460XVR
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My comment in post #4 about the bullet bouncing off the top strap was "tongue in cheek". Hope your comment is too.
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stonebuster
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So shooting 130 grain 38 specials wear forcing cone more than 158 grain 38 specials?
Probably but erosion at 38 special pressure is going to be so slow it would take thousands and thousands of rounds.
Even with full tilt boogie 125gr@1450 357s it'll take many many rounds to erode even a K frame to the point of damage.
Not enough to ever make any difference. Once you've spent $10,000+ on ammo a little wear from .38 special is not going to matter.
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