Forcing Cone Erosion

[NAKing]

I have a .357 magnum revolver that I've put probably 300 rounds through over a couple of months (158 grain JHP magnums). When cleaning the revolver I noticed that the inside edge of the forcing cone is not really sharp like the outside edge. Is this forcing cone erosion? Is this normal for a weapon that has been fired so little? What can be done to slow the progression of this down?

[Smoke & Recoil]

Unlikely erosion, more likely lead and burnt powder billed up. It's easily
removed with a brass screen and Hoppies #9 pulled from the muzzle
end. If you would like to buy a kit for this purpose, you can get it from
Brownells, look for Forcing Cone Cleaner. Hope this helped.

[polixines]

what is the gun

[madmag]

I clean my forcing cones using a dental tool. The kind that has a 90 deg. bend and sharp on one side. I have the area wet with bore cleaner. NO this does not hurt the metal of the cone. With just light pressure the crude comes loose. I have a hard time getting it loose with just bore cleaners and brushes. Been doing it this way for 40 plus years. No problems so far.

When cleaning the revolver I noticed that the inside edge of the forcing cone is not really sharp like the outside edge.

That's OK. You don't really want a sharp edge, that just promotes wear.

What can be done to slow the progression of this down?

Not much if it's due to powder burn. That's just part of the equation. But should last many thousands of rounds with no problems. Well, don't shoot mags as much, use .38spl.

[polixines]

good idea about the dental cleaner.

[madmag]

Or you can buy this. Looks like ti works well.


http://www.brownells.com/aspx/NS/GunTech/NewsletterArchive.aspx?x=v&p=0&t=1&i=889

[NAKing]

I don't think it's powder buildup. I use Hoppes 9 religiously after every range trip. The good news is that it sounds like a little rounding of that edge is normal. Whew!

I don't shoot heavy loads. It's a Taurus M66 4" 7 shot stainless. I reload Hornady XTP (158 grain) with 7 grains of Unique.

[Socrates]

I thought forcing cone errosion was from using very light bullets, with large powder loads?

[madmag]

I use Hoppes 9 religiously after every range trip.

I can only relate my experience. I also use Hoppes and other good bore cleaners, but they will not remove the forcing cone buildup. I guess partly due to the fact that there is a lot of heat flash and other materials involved....not sure.

I thought forcing cone errosion was from using very light bullets, with large powder loads?

Good question, I am not expert enough to answer. Maybe someone else has experience.

[Socrates]

It's caused by the ftlbs of energy of a light bullet being slammed into the forcing cone at high velocity. Seems the slower bullets impact the forcing cone with less force...

[rogertc1]

What Kind Of Gun Is It?

[NAKing]

What Kind Of Gun Is It?


It's a Taurus M66 4" 7 shot stainless. I reload Hornady XTP (158 grain) with 7 grains of Unique.

I'll try to take a picture of it.

[NAKing]

Here we go. I finally got a picture that didn't come out blurry. ;)

http://artificialhorizon.files.wordpress.com/2008/09/forcingcone.jpg

The inside edge used to be as sharp as the outside. I tried picking the black off with my fingernails and wire brush. I don't really think gunk could build up that far like that without causing cylinder clearance problems. It seems like the metal is actually worn on the inside edge, but I'm a newbie, so possibly not. :rolleyes:

The cylinder barrel alignment is perfect for all cylinders and the weapon is still nice and tight.

[madmag]

I did look at some of my forcing cones (including .357 mag) , and I must admit they did not have the wear you show. Mine are not sharp but just a slight chamfer. Not saying yours is a big problem, but it seems to be a lot of wear.

[Gatorhugger]

Its not lead obviously and if it used to be sharp then that is some soft metal to end up that way. I don't care how many shots.

That said, I doubt it will affect anything at all. By the time the bullet enters the chamber it already sealing the gases so a slight "lip" shouldn't hurt and thing.

I would keep an eye on it, but would not worry about it unless it worsens considerably.

[NAKing]

Great! :(

If the cone erodes further the gun is pretty much toast, right? I've just had it for a month.

[madmag]

If the cone erodes further the gun is pretty much toast, right? I've just had it for a month.

That is the main worry. Sharp edges wear fast at first, so now maybe things will slow down.

Back to your original post.
When cleaning the revolver I noticed that the inside edge of the forcing cone is not really sharp like the outside edge.

Are you sure it did not come out of the box this way?

The inside edge used to be as sharp as the outside.

Sorry, you already answered.

[NAKing]

I inspected the revolver throughly before purchase with the information in the revolver inspection sticky. It easily passed all tests.

[madmag]

I don't want to add to your concerns, but when I look at the photo I keep thinking soft metal. Now barrels are not super hard in the Rockwell range. They can still be drilled. When you get above RC 55 things get very hard to drill with normal drills. But barrels are not supposed to be completely soft either.

So, shoot some more and keep close check. If the wear continues then I would consider having the barrel hardness tested or send back to Taurus. If the wear does not get worse, then what you have will probably not be a problem.

[Gatorhugger]

I really think the barrel was not hardened properly. How's the topstrap look? Any flame cutting?
I have old Smith revolvers that I have shot 10 times as much with less erosion. Mine just has a tiny bit in the 6 oclock position. On the worse ones.

Your gun has that uniform ring, and that is just wrong.
It definitely isn't right in my opinion.

[Kreyzhorse]

I'd keep watching it and if it continues, give Taurus a call. Right now, I wouldn't worry about it but I'd keep an eye on it.

[NAKing]

The top strap shows just a very faint line. It does not seem to be cutting at an accelerated rate. I think I am going to have a gunsmith look at it.

[madmag]

The top strap shows just a very faint line.

That's normal, but the gunsmith is a good idea for the forcing cone.

[NAKing]

I had a gunsmith check the forcing cone out. He said the wear is even and normal. I guess I'll just keep shooting then. :)

[madmag]

I had a gunsmith check the forcing cone out. He said the wear is even and normal. I guess I'll just keep shooting then.

Good news. We all learned something.:)

[James K]

Any time a fluid moving at high speed is forced through a small opening, it speeds up (think garden hose with an adjustable nozzle). With powder gas, that means the gas flow becomes very fast and anything in the way is burned, just like holding an acetylene torch to it, as well as abraded by burning powder and particles from the primer.

In rifles, the direct cause of throat erosion is that the case neck expands and the bullet is released, but does not move right away because of its own inertia. So the gas flows around it at very high speed, burning and eroding the barrel throat around and ahead of the bullet. As the bullet moves forward, it seals the barrel and erosion stops. As firing continues, the erosion moves further and further forward until it eats out the initial rifling and the bullet begins to tip and skid, causing inaccuracy.

The same thing, on a lower pressure scale, happens in a revolver. The bullet moves out of the cylinder and into the barrel, but the gas is moving faster and flows around the bullet, eroding the forcing cone. Obviously, this will happen more with "hot" loads, but it is almost inevitable with any loads. The same constrictive effect is seen in the barrel/cylinder gap and in topstrap cutting. The effect on the cylinder is less because the steel used in cylinders is harder than that used in barrels.

Jim

[madmag]

The effect on the cylinder is less because the steel used in cylinders is harder than that used in barrels.

First, good job on your description. But I disagree with just the last statement. I think cylinders are about the same hardness as barrels. The difference is that the gases are leaving the cylinder and not doing the damage as with forcing cone. Anyway, minor issue.

Steels used to make guns are not brought up to full harness. They would be almost impossible to drill & tap, and would be brittle to boot. Tool steel can be brought up to RC 55 to 65 (more if you use D2). That's too hard for normal gun use.

[gscrasher]

NAKing,

I looked at half dozen of my .357's and saw a similar type of wear on only my oldest, a Ruger, GP100. This gun has fired thousand's of rounds of all types, including many full power magnums. Your load of 7 grains of Unique behind 158 grain JHP bullets is not particularly hot according to the latest Speer manual. Doesn't seem like there should be that much wear after 300 rounds.

As an aside, the Lewis lead remover does work as advertised. However you say you've been shooting jacketed bullets, so you don't have a leading problem.

I know this doesn't help much, but your wear will probably slow down now, as mentioned by another poster. Just go ahead and shoot it like you borrowed it, you'll probably forget all about it. Good luck!

[NAKing]

No, it's not a particularily hot load. I find 7 grains has the best accuracy for both the shooter and the gun. It shouldn't put undue stress on the firearm. I'll just keep shooting. :)

[Mark Milton]

Something to keep in mind vis a vis the medium or "K" size frame .357s...

That frame was originally designed for the .38 special.

When Bill Jordon masterminded the Combat Magnum design there were no 125 grain jacketed hollowpoints.
Light weight superfast magnums wreaked havoc on K frame size revolvers with topstrap cutting and forcing cone erosion and cracking.
Which was why Smith and Ruger came out with bigger framed guns like the L and GP series.

I have two K frames and I usually shoot .38 plus p through them and use full house magnums in my L frame.

[NAKing]

I think I'll switch to .38spl. I want this thing to last because I like it! :p

[madmag]

I think I'll switch to .38spl. I want this thing to last because I like it!

Good idea, now all you have to worry about is that nasty powder ring .38spl leave in .357 chaambers......if it's not one thing it's another.:p

[Sport45]

Run a WET solvent patch (I like Ed's Red) through the chambers and let set a minute or two. Then a .40 bronze brush chucked in a drill will take those rings right out.

[roadrash]

Since you reload,just download your .357 cases to .38 special levels for target shooting.

This will eliminate the powder ring in the cylinder problem.

A pound of bullseye lasts forever.

[NAKing]

Okay, good. I didn't want to have to buy cases and other goodies just to keep reloading at a lesser power.