What causes forcing cone erosion?

[Porterhouse]

Hi all.
I’ve been wondering this for as long as I’ve been reloading but never got clear answer.
I put close to 3,000 rounds through one of my .500 S&Ws and see obvious erosion on the forcing cone as well as gas cutting on the top strap. The most of the loads I used are 525gr cast with 47.0gr AA1680/WC680. I hear a lot about ball powder blasting the cone but in the book UNDERSTANDIN BALLISTICS, author Robert Rinker says “Double-base powders burn very hot and have reputation of being rough on barrels. On the plus side, they produce high velocity at low pressure” (P.29). Sooo, it seems like the erosion is the result of high heat created by the Double-based ball powder and not the direct result of powder particle blasting the cone. If that so, if I want to choose longevity of the gun over higher velocity, should I stick with single-based extruded powder? Any thought on this?

[buck1]

I was going to buy one , but I read that they had probs in the forcing cone dept. From what I heard if the slightest imperfection was in the forcing cone they would erode very very fast. And faster on the 460 . S&W was to have a method to make them flaw free but I didnt buy in to it. I would be calling S & W. FWIW.....Buck

[felix]

Just lower the pressure. Yes, double base powders burn hotter than single base powders. But, for your purpose, lower the pressure to about 35K, and call that your max fun. For min fun, consider 25K as a working everyday load. To gain accuracy and good burn, you will need a powder that works at those lower pressures. They are called shotgun powders. Try and find loads using BlueDot. If you want a little cooler burn, then use N105 at the same grain weight. N105 is probably the most expensive powder out there, but nil considering the cost of your gun. ... felix

[44man]

I agree with Felix. Heat and the sandblasting effect of powder combined with hot gas cutting can do in a forcing cone. The .357 max was really eating them up and was one of the first to cause trouble.
My .44 is eroded a little but I have 57,665 heavy loads through it.
On the other hand, my BFR .475 shows no sign of it after many, many shots. It cleans up shiny. Although loads are fairly hot, the pressure is not that great. All I have used is 296 too.
The whole problem is that most of us buy a gun for power, long range, accuracy, and hunting. It is hard to shoot pipsqueek loads. Easier to grab a smaller gun for fun shooting. Hard though, I grab my .475 or 45-70 BFR's first, just too much fun. My .22's, .44 and .45 are sagging from not being used. They have that hangdog look!
We have to pay for performance one way or another.

[Whitespider]

HOLY COW! 44man,

57,665 rounds! In one single revolver! Wow, that’s like 100 rounds a week for 11 years. Or 50 rounds a day for 3 years. Or.............

I have a couple of revolvers that are approaching 10,000 and one that’s well over that.

Burst my bubble, I thought I shot a lot.

[45 2.1]

57,665 rounds! In one single revolver!

Thats not really a lot thru one gun, believe me.

[Bass Ackward]

Porterhouse,

Erosion of the forcing cone is caused by powder impact and heat. Flame cutting of the top strap beyond normal wear, can be from something totally different. You can get more of one disproportionately without so much to the other.

Shooting softer lead can increase time in the forcing cone which obviously allows more pressure to escape. Elmer Keith used to believe GCs increased cutting of the top strap. Not sure the logic there. But anything that delays forward progress of a bullet (increases barrel time) like a constriction, or rough spot in a barrel, or non slippery lubes, or throat fitting bullets if they are much over bore diameter, and barrel leading can increase flame cutting of the top strap. So will end play of the cylinder if this widens the BC gap on certain chambers. These are just some off the additives to normal wear off the top of my head between the first and second cups.

There could be a bazillion reasons that you might be able to diagnose to .... retard this as much as possible, but cutting pressure and using faster powders are the sure cures.

[44man]

This was my silhouette gun and I started counting the primers I used in it. It's the only gun I ever did that with. It's the 10" stainless and I bought it the first year it came out, been a long time.
I have always used STP on the pin and ratchet and it is still as tight as the day I bought it. Then I never pull back the hammer fast either.
It never fails me on deer now.
Talking about pin lube, my friend just got back his Freedom and cleaned it before shooting it. He could not move the cylinder pin. I told him to put some oil on it and leave it sit awhile. It was still hard to pull out. Now with STP on it, it slides in and out real nice. I don't know what the factory lubed it with but the lube failed with just their test firing. Most oil will fail from cylinder gap flash and pressure but STP seems to hang in there. I can even fire my cap and ball all day without sticking the cylinder. RCBS case lube also works good.
I keep the STP in a plastic bottle with a little spout. Only takes a drop or so and this is the STP I bought maybe 30 years ago. Now, that is CHEAP.
I have tried everything over the years and nothing else held up, so if you have a fine revolver, you might want to try STP. It's a little hard to get into a double action but if you put a drop at the front and prop up the gun, it will creep in. A little is better then none.

[arkypete]

Isn't this the same problem that the 357 Maximum had, causing that caliber to be discontinued?
Jim

[Newtire]

Talking about pin lube, my friend just got back his Freedom and cleaned it before shooting it. He could not move the cylinder pin. I told him to put some oil on it and leave it sit awhile. It was still hard to pull out. Now with STP on it, it slides in and out real nice.

I agree wholeheartedly about the STP. I tried anti-seize too but nothing beats STP. Just don't spill the bottle, makes a helluva mess.

[Porterhouse]

Now, I got confused again.

44man -,
What powder was used for your 44mag? I have several 44s and all of them have erosion & gas cut and the powder I use are mainly 2400 and H110.
Also, about your .475, you said you use fairly hot load with 296. That is a double-based ball powder with hot gas compare to, say H4227 isn’t it? And, from what I understand, .475 operates on high pressure but has no sign of erosion?
Humm… how do I achieve that with my .500.

Bass Ackward -,
I understand the approach of using faster powder/lower pressure but one of my .44 has had erosion showing after only about 5,000 rounds of 250Keith - 9.5gr Unique. I no longer use faster powder for .44 since then. On the other hand, I have put tens of thousands of 148gr HBWC with W231-3.5gr through a S&W M27 and I don’t see any noticeable erosion.
I just feel like 100% load density is safer (no chance of double charge) and consistent in general but what do you think?
The above mentioned 47.0gr of AA1680/WC680 gives 1,400fps with 525gr out of 6.5” barrel and that’s more than I wanted. But since it is so consistent, no sign of too much pressure (cases literally fall out), I settled with this load.
But now, with this erosion issue as well as it’s excessive recoil, I’m starting to think that I should revisit my experimentation. Although I haven’t crono yet, H322 (46.0gr) is giving me good result so far. Seems accurate, good velocity, and tolerable recoil. But again, I’m not sure if it’s really easy on the forcing cone…

[felix]

Assume that all smokeless powder burns correctly at 4000F. Question? How long is that temperature at the forcing cone? How much of that heat is transfered from the powder to the gun, and for how long at any one particular spot/section? These are the questions, while constantly keeping in mind that different deterrents force the 4000F to migrate further down the barrel. Powder that is not burning correctly will never reach that temp on AVERAGE per molecule of burn. Pressure is required to make that happen to each and every molecule of powder once ignited. Nitroglycerin requires less pressure for the same continuous burn, and requires well designed deterrents to help keep the powder from being way too sensitive for gun longevity. ... felix

[Bass Ackward]

[QUOTE=Porterhouse;193811]Bass Ackward -,
I understand the approach of using faster powder/lower pressure but one of my .44 has had erosion showing after only about 5,000 rounds of 250Keith - 9.5gr Unique.

I no longer use faster powder for .44 since then. On the other hand, I have put tens of thousands of 148gr HBWC with W231-3.5gr through a S&W M27 and I don’t see any noticeable erosion.

I just feel like 100% load density is safer (no chance of double charge) and consistent in general but what do you think?QUOTE]


PH,

Understand that wear is relative. My dad shoots nothing but 9.5 grains of Unique with a 250 Keith in his Redhawk. I can't tell you how many loads exactly, but I suspect I have fired 10-12 thousand since 1980 through THAT gun myself. He has virtually zero erosion. But his gun was fire lapped. That means that his bore is open to his throat size so little forcing cone is visible anyway.

But look at this realistically. Your 500 isn't a 38 Special. It is what it is. Gun life should naturally be below a 38 Special. And so you should expect a little more wear than say your 44. If you hot rod your car, it won't last as long either, right?

But back to your 44, guys have been shooting quite a few bullets of all persuasions using Unique for quite some time. Since 1898 I believe. If forcing cone wear were a powder related phenom more than other powders, then the word would be out by now. Bear in mind that for the first 50 years of Unique's existence, barrel steels were much softer and prone to erosion effects. I am not trying to defend Unique here. My point is that your wear has to either be a poor HT of the barrel steel or somethings else that's going on. So maybe you should investigate why.

Please don't take this the wrong way, but you aren't seeing carbon and lube buildup and mistaking it for forcing cone abrasion are you? I have had that before, especially from guys that were allergic to bore brushes and cleaning in general. :grin:

Load density is a personal thing. I feel the same way about my ability to throw a double charge. Question for thought: Is 100% load density any safer than say 60%? A double charge at 60% is still going to be 120% and stick out like a sore thumb.

[44man]

Porterhouse, I use 296 as it is the most accurate. I also use Fed 150 primers. All of my loads are the most accurate for each bullet/boolit and are under max. The very inside edge of my forcing cone shows pitting and rounding but the rest will clean up nicely. There is no cutting of the top strap that I can detect. I am not concerned with it at all because I recently broke 1" at 100 yd's with the gun and a cast boolit.
What might have helped is when I first bought it, I opened the forcing cone to 11 degrees.
The BFR .475 is hard to explain! When I clean the gun, the forcing cone shines. My BFR 45-70 is the same. I look at them in amazement. They have been shot a lot. It might have something to do with bore size, boolit pull and boolit weight.
The problem with the .357 max and frame cutting was the smaller bore and the intense flame at the cylinder gap. My Ruger showed this cutting but Ruger said it would not hurt anything and would only progress so far and stop. That was the most accurate Ruger I ever had. I shot a 39 the first match with NO sight settings. Shame they quit making it and I will always regret selling it. Seems as if a stellite (Spelling?) insert would have cured it.
Freedom once offered a special forcing cone insert. I wonder why they stopped.
The bottom line is that if the gun still shoots, don't worry about it too much unless you start to see splits.
I have an idea that too tight of a cylinder gap can increase erosion and cutting because of jet effect. The smaller the gap, the higher the pressure. I never measured my BFR's because they shoot so good, I don't even want to know.
Oh yeah, some of you clean the bore but not the forcing cone. What fits the bore is too small for the forcing cone so you might just have dirt.

[Porterhouse]

[QUOTE=Bass Ackward;193831]
Please don't take this the wrong way, but you aren't seeing carbon and lube buildup and mistaking it for forcing cone abrasion are you? I have had that before, especially from guys that were allergic to bore brushes and cleaning in general. :grin:

- No, unfortunately. I checked with 20X magnifying glass and it is obvious that metal is eaten away.

Load density is a personal thing. I feel the same way about my ability to throw a double charge. Question for thought: Is 100% load density any safer than say 60%? A double charge at 60% is still going to be 120% and stick out like a sore thumb.

- Good point. But what about consistency? I get good Standard Deviation when it is 100% or slightly compressed and that is true with three rifle powders that I tried with .500.

[Lloyd Smale]

Like was said heat is what the enemy is. Ball powders are notorious offenders. Another thing that wasnt touched on and is probably one of the most important ways to save on wear is your shooting habbit. YOu take that big 500 with 35 grains of ball powder and fire a clyinder full in da and feel how hot that gun gets. Now go to the range and the first thing youll see some inexperinced handgunner that just got his 500 and wants to impress his buddys does. He loads it up and lets loose. You got to figure he just shot the equivelent of about 25 357s in a matter of about 4 seconds though that gun. No gun will take abuse like that. Another thing is just about everyone with a big gun wants to load it up to the max to impress everyone. Drop the velocity 200 fps and you probably double the life of your forcing cone.

[44man]

Lloyd, nice way to say it. You are correct. Take care of the gun and it will last a long time. I would rather impress friends with accuracy then recoil and speed. One accurate shot is worth 1000 noisy blasts when nothing is hit. My new friend from this site, that I found lives close to me, is a fantastic shot and just can't believe the accuracy of a good revolver at LOOOONG range. He always read my posts with a grain of salt but now that I have had him do it himself, he is a believer.
To load for the most recoil and velocity from any decent gun is always wrong. I will never understand why some quote how fast their guns shoot. Show groups instead, that will impress more!
Think about it! How many long range groups from revolvers have been posted on this site? I don't remember any except mine, just talk. Tone down the loads and find accuracy first, nothing else matters.

[Porterhouse]

Lloyd Smale & 44man,

Yes I agree, accuracy is what I want.
The problem is this load is not the max for the gun and it just happen to be the most accurate load I found so far. I haven’t done serious group test yet and I don’t think I can get 1” at 100yds but good enough for 200 – 300yds prinking.
BUT, I got it;
Burning lots of DOUBLE-BASED BALL POWDER = Heat = Wear
Sooo, either I have to live with it or do something. Correct?

[Lloyd Smale]

Either switch away from a ball powder which is tough to do if you want high velocity as most powders that will get you there are ball. Or you back down your velocity a 100 or 200 fps and try different powder primmer alloy combinations to get your accuaray back to the level that your happy or you live with it. Like i said just common sense with your gun will save most of it. Dont get your gun so hot that you cant touch it. Bring two or three guns to the range and switch back and forth to keep them from getting so hot they glow. I get a kick out of guys working up loads with a handgun. If there shooting there rifles there shooting 3 or 5 shot groups letting there barrel cooled between shots and certainly between groups but give them a handgun and they pound a 100 rounds through it a fast as they can lood and shoot and then wonder why there gun has a little forcing cone wear. Take your 270 and shot it that fast for a 100 rounds and do it 15 or 20 range sessions and see what the throat in it looks like!!!

[Bass Ackward]

Sooo, either I have to live with it or do something. Correct?


PH,

Absolutely.

Back in the late 60s I made a 30-378 WBY. Throat erosion was severe. Out until it stabilized. Then it wasn't so bad. But over the life of that gun, it had three barrels on it. If I want to dance to the tune, I gotta pay the fiddler.


My point, so you lost a little metal. We all do as they .... break in. I consider this just part of the process. I also watch this process for clues of how things are going to determine if there are any problems. Example.

Just had a Redhawk I am working over that was wearing the left side of the forcing cone. Closer inspection showed the pad in the frame that was responsible for support of the crane assy was being decimated. The hole for the cylinder retention pin in the crane was being imprinted into the pad. The gun was in the process of correcting an alignment problem that I didn't want.

Stoned that up and got rid of all the burrs and things got better. Then I went to lead and was leading down the left side of the cone. So I stoned a couple of .000 off the crane pad again. Leading has stopped and the gun is now in a position to lap and correct the previous wear pattern or simply use as is.

Do you catch my point? All cone wear doesn't have to be from powder or bullet or load. That gun is going to make itself shootable one way or another.

And you are right about load density and accuracy. I like 90% and up for rifles. But there are two ways to improve load density in handguns. One is powder speed. Another is bullet. The deeper a bullet is seated, the faster pressure will come up and burn rate can increase dramatically helping to burn slower powders. Deep seating meets your criteria for cutting forcing cone wear.

Consider yourself lucky. Many people have to pay to get a taylor throat cut in for them and your gun is doing it for free!!!

We have given you many things to think about. And in truth there could still be a HT problem that you can not see. So we are back to your statement above. Expend as much effort as you desire or change load conditions to correct the problem to your satisfaction and take solace that you did what you can and just enjoy it while it lasts. Shoot it. What's the worst case? You have to have the barrel set back one turn and recut the cone every so often? Shoot it.

[Lloyd Smale]

bass makes some good points a gun is mechanical devise that is going to wear no matter what you do. Your not going to total stop it. They dont last forever. Nice thing is that the average guy will never wear a forcing cone out so bad that accuracy suffers and like he said they can be recut if you keep your eye on them and dont let it get to bad. Had to chuckle (well i didnt really chuckle) at camp 2 days ago. Ive got a cheap oly ar 15 that is the camp fun gun. Everybody grabs it and blasts clip after clip out of it just to make noise. I never cared as it never shot well anyway. I took my new colt hbar match target out there the other day and my dad ask me if he could try it. I said sure. I was accross the yard doing something else and what do i hear but my sub minute of angle ar going about full auto. I came running (if you can call running with a cane in pain running) screaming at the top of my lungs to cease and desist (not the words i used!!) Point is that if you want to go and blast a bunch of rounds and have fun thats part of handgunning. Just grab a cheap ruger that you have designated for that. I allways have a cheap blackhawk that is a plinker. One that i dont care if it shoots tiny little groups that i can abuse on days i feel the need to do that. If it ever does wear out, which i doubt it will i can either rebarrel it or give it to someone else to do the same. Actually the only guns ive ever wore the forcing cones out on were a security six ruger (they were notorious for soft forcing cones) and a 15 smith that had probably well over a 100000 rounds of little 105 lees using ball powder. I think in both cases the rebarreling was about a 100 bucks and came with a free reblue (that was badly needed with both of them) So if you figure the cost of the wear it was pretty insignificant. Now rebarreling a rifle isnt a cheap proposition and a guy needs to even pay more attention to how your treating one of them.

[Porterhouse]

Thank you all,

Now, this leads me to another question and I’ll post that in Design section.