Forcing cone/top strap erosion

[DonD]

Over the years I've read many posts by people saying such and such a powder, usually a ball powder, results in serious and often unacceptable forcing cone erosion or "cutting" of the top strap.

Since I have a modest relationship with one of Hodgdon's senior powder gurus, Ron Reiber, I asked him what his thoughts are. He's pretty blunt that the claims of severe erosion from ball powders are a myth. Here's what he said.

"People have various opinions regarding top strap erosion, but, they do not know the facts. Yes, some are slightly worse than others, but not excessively so. IMR 4227 is a single base propellant with a flame temp less than the ball powders. Ball powders with more NG content have a higher flame temp and give a bit more erosion. How much? Takes thousands of rounds to overhaul a forcing cone with any of the available powders. The difference is small enough that one could not tell which was the worst. There is more variation in barrel steel than the effects of erosion by different powders. In other words, ignore their claims, and shoot what works best in your gun. If and when erosion becomes a factor, new gun or new barrel, problem solved!"

To me, that says the issue is just another internet myth. Don

 

[Chuck 100 yd]

That statement should get the stories flowing. I have not experienced any problems personally but rarely load hot loads and seldome use ball powders either.

 

[22/45 Fan]

I always use ball powders in my 686, first WW231 and now Titegroup. After about 15,000 rounds, both the forcing cone and top strap still look brand new. Now, those were almost all all fairly mild .38 Special loads so I wasn't generating huge pressures but if ball powders inherently caused problems I expect I would have seen it by now.

 

[Dan in MI]

Did you ask him about a 357 Maxi?

 

[jsh]

I believe it was him that said trail boss was a good replacement for SR 4759......
I would like the low down on lil gun as well.
Jeff

 

[DonD]

I believe it was him that said trail boss was a good replacement for SR 4759......
I would like the low down on lil gun as well.
Jeff

Reiber likes LilGun, has said so in several emails I've had with him. That and H110 are the go to powders for max loads in my .500 Mag. Don

 

[David Bradshaw]

Don.... good of you to recount the experience of Ron Reiber. (Prior to Reiber landing at Hodgdon Powder, now many years ago, he served a hitch at Hornady.) Heat and pressure multiplied by time applied erodes steel. Except with a frame made from junk metal, top strap cutting is a non-issue. Barrel face erosion, which we commonly call forcing cone erosion, affects a revolver exposed to high pressure loads. More powder loaded to higher pressure generates more heat and flame exposure. This should not be taken by beginners nor anyone else to suggest maximum loads of medium burn-rate powder is a substitute for selecting a propellant correct for high velocity loads.

During development of the .357 Maximum at Ruger, quantities of Hercules 2400, Winchester 296, Hodgdon H110, IMR 4227, and Hodgdon 4227 were loaded, along with Winchester 680. Notice not a single fast or medium propellant factored into development.

Light bullets launch faster and take more powder, exposing the barrel face to more flame. "Flame" as a euphemism for combustion. To back down just a little below full magnum loads slows erosion. This is true whether the cartridge be .357 Magnum, .41 Mag, .44 Mag, .357 Maximum, or .454 Casull, and the reduction prolongs brass life.

The cure for severe forcing cone erosion generally is to set back the barrel. Most shooters will not experience the need in their lifetime. It is far more important to load carefully and to become a marksman or markswoman than to worry minor wear on a fine revolver.
David Bradshaw

 

[DGW1949]

So....how's about the effects of erosion caused by the impact of the "as-yet unburned powder" being spattered against the steel as it (and the projectile) is being launched?.....at X-amount of speed/pressure, does that type of erosion not increase with the use of ball powder?

Not sayin' that it does, just asking because I've allways heard that it does.

DGW

 

[jsh]

My question on the lil gun refers to FA's comments on it. I have quit using it in wheel guns and still use it in a couple of rifles and TC barrels.
I like the stuff with heavy cast bullets, exceptional accuracy and speeds. I know a lot of folks have kicked it to the curb over this. I don't recall what loads nor bullets were used with the issue in question. I emailed hodgdon about this around thanksgiving and never got a reply.

 

[David Bradshaw]

Developed impression long ago that mag charges of slow ball powder had a sandblasting effect on barrel face. The .357 Maximum contributed to the impression, but my shooting with .357 Magnum and .44 Magnum revolvers forced me to conclude erosion proceeds from pressure, time, and heat. Ball powder implies a double-base propellant----the inclusion of nitroglycerine----which generally burns hotter. The longer burn time of a slow powder should never, never be used as an alibi to attempt top velocity with a fast powder. Pressure will spike without ever achieving desired velocity. Therefore, the longer burn time of an appropriate slow powder has time to accelerate from a dead stop a heavy bullet. This longer burn time continues to accelerate the bullet and do so without turning the cylinder into a hand grenade.

Take a tip from an old powder monkey: it takes longer to push a rock than to shatter it.

I have had the barrel set back on .357 and .44 revolvers which diet plans included 2400, 4227, and 296/H110. Pressure of full house loads seems to be the greatest factor. I still think ball powder exhibits what I call a sandblasting effect, yet, many round down range later it remains conjecture. I believe the same effect is seen on the bolt extension and the flash hider of AR-15/M-16's.

Jim Stekl of Remington BR fame and the Bench Rest Hall of Fame, told me he cooked a bench rest barrel almost immediately with a ball powder, with fouling fusing to the bore which could not be removed. Stekl is not an alarmist.

Jim Stroh of Alpha Precision rebarreled a Freedom Arms .44 to my specification. To date its main source of energy has been Win 296 and H110 (same powder). My concession to erosion is to back off the charge just a hair. Example: Sierra 240 JHC over 23.4/296 or H110. Which is good enough for 3 to 4-inch groups at 300 yards. Brass lives on-and-on and long brass life is a good thing. Concepts like consistency and forgiveness count big time.
David Bradshaw

 

[SBH4628]

Hey David
Are you just talking 357 Maxi?

 

[David Bradshaw]

sbh4628.... you caught a self-inflicted typo, my saying ".357 Maximum" where I meant .357 Magnum. The .357 & .44 mags, and .357 Maximum fed steady max loads, all 'em eat at the barrel face, i.e. forcing cone. As you know.

Never heard a silhouette shooter worry about forcing cone erosion.
David Bradshaw

 

[SBH4628]

I understand David...what is your answer on a 50 year old smith,cast bullets only.Be nice...It was my late fathers gun. I can post pics later. Many 1000s of rounds. Still a fine old gun.

 

[David Bradshaw]

Fifty year old Smith, father's gun. Is it an M-27 or M-28 .357? Or, a Model 29? Lead bullets fed Hercules or Alliant 2400 a few grains below maximum charge tend to be accurate, especially with deep seated to crimp .030"-.040" above front band. A .357 will not tire of shooting 158 SWC seep seated over 12/2400. This load is fine for extended consumption in M-19/M-66 and as accurate as the bullet itself.

Nor will an M-29 .44 Mag tire of shooting a cast 240 or 250 SWC deep seated over 17/2400. Accuracy should be superb well beyond any practical distance.

Same loads work perfectly with swaged half-jacket SWC and SWC HP, deep seated.

Primed most of these loads with CCI mag primers.
David Bradshaw

 

[BIgMuddy]

Have personally seen FA 454 that had a forcing cone that looked new after 20+ years and 1000+ rounds with H110. Same gun showed cone erosion with 50 rounds fired with Lil Gun. I own a FA 454 that was doing fine with H110 and the cone was ruined with 200 rounds of Lil Gun. That gun now re-barreled is doing fine, most rounds with 4227. Another of mine showed minor erosion with as few as 50 rounds and I had that barrel set back.

Myth? Nope. It was concluded and I think as David stated, it is the heat generated with Lil Gun that is the culprit. Maybe it would have worked out ok if the loads were
backed down a bit. "New gun or new barrel problem solved". That's funny. Buy another gun in excess of $2K instead of changing powder. (or a new $400+ barrel)

Dan