Cylinder Throat erosion

[castmiester]

I know about rifle throat erosion and keeping track of OAL in my loads, but was wondering about keeping track of revolver throat erosion. Thanks.

[Bigslug]

Rifles to revolvers will not be an apples to apples comparison. Revolver cylinder throats are a smoothbore funnel that guides a bullet into the forcing cone, which is yet another funnel to guide the bullet into the rifling. Diameter - i.e. wearing outward - is going to be a bigger factor than the wearing forward we seek to track in rifles.

Tracking cylinder throat diameter would be easy enough to do with pin gauges. Tracking barrel wear from the forcing cone forward would be easy enough by using the next larger pin gauge up from the one that will slide completely through the bore - assuming that any frame crush has been lapped out of it. You might need to shorten that pin gauge to fit inside the frame window, but as long as you knew how far forward it would go on a new barrel, the deeper it goes is your wear measurement. You might need a fatter bullet at some point in the far off future.

Personally, I think this would be one of those "Quests that drive men mad" topics.

If you've ever played with a commercial 5.56/.223 throat erosion gauge, most of them have a series of tenth inch lines to allow you to measure wear to a depth of about an inch and a half.

I've you've every played with a MILITARY 5.56 throat erosion gauge. . .that sucker will fall at least three inches down the barrel before it gets to the line that says "don't deploy this rifle overseas if it gets to this point", but they still call it a "serviceable" rifle approaching that much wear, and many of them will still deliver acceptable accuracy within the service rifle's stated "effective range".

Colt and S&W both made match-tuned automatics chambered to shoot .38 Special wadcutter loads based on the notion that it was easier to get repeatable accuracy out of one chamber behind the barrel than six.

Having a revolver's chambers all be exactly the same dimensionally, and having them all lock up identically behind the forcing cone is one of those things that a super high end revolver like a Freedom Arms manages pretty well, but it's an area where "good enough" has gotten it done for almost 200 years.

At the point you have enough rounds fired to be tracking barrel and cylinder throat wear at handgun intensity levels, I'd be more worried about the lockwork starting to fall apart. Add in the human-behind-the-trigger factors associated with handgunning, and you may start to question the sense behind the dive down certain rabbit holes.

In short, if it shoots, call it good. If it stops shooting, evaluate.

[castmiester]

Mechanical thing’s dropping off before that would happen yes, but along the way, no erosion. Ok

Doug mentioned about how hard Ruger cylinders are and l was impressed. They buy thier steel already treated and it’s extremely hard. Maybe, if l remember right, that’s one of the reasons why he went to honing instead of reaming.

[Bigslug]

Another anecdote of how hard it is to kill a pistol barrel. I think it was in Precision Shooting Magazine. . .Kevin Thomas related his time working for Sierra Bullets. They had a barreled firing fixture chambered in .45ACP for accuracy testing every lot of their match bullets. The same barrel had been on that fixture for perhaps decades before he arrived. I want to say he conservatively guestimated 20,000-30,000 rounds and there was no reason seen to retire it. That article was written probably over 20 years ago. It wouldn't surprise me if it's doing the job still.

That magazine had a good amount of discussion about factors in RIFLE throat wear. The high pressure heat obviously was one of them. Another theory bandied about in discussions of cartridge shoulder angle was the yet-to-ignite front of the powder column getting sandblasted forward into the throat by the primer and igniting base of the charge behind it.

Smaller, softer granules of powder in the handgun propellants. Faster burn more inside the case. Quicker and lower peak pressures. Less heat. If we're talking cast loads of someone who knows what he's doing, probably better bullet fit than with jacketed and less chance of flame cutting on either bullet or barrel.

So yeah. . .I'm thinking if you write your throat and barrel measurements down on some REALLY durable Egyptian papyrus and store those notes in a purged nitrogen environment, somebody in the far off future can check the gun to see if it's opened up any.:lol:

[JonB_in_Glencoe]

If you like to use Lil'gun for near max loads in Magnum revolvers, then I would recommend tracking erosion.

Here is a good conversation about it.
https://castboolits.gunloads.com/showthread.php?297894-Revisiting-Lil-Gun-issues-brought-up-in-the-past

[Forrest r]

Erosion can occur were the brass ends in the cylinders. Hot powders will have more of an impact. Hot powders ='s h110, mp-300, 2400, aa#9, etc.

Not the best picture, what a 586 cylinder looked like when retiring it. I has "steps" burned into it.
https://i.imgur.com/DuGkwVF.jpg

[jrayborn]

Any idea how many rounds that took?

[Forrest r]

+/- 275,000

[jrayborn]

I thought it might be a "fairly" large quantity. :)

[stubshaft]

When Freedom Arms brought out their FA83 they offered a tungsten steel insert to eliminate any erosion on the forcing cone area of the barrel. Since I had just trashed and cracked the forcing cone of my Ruger 357 Maximum barrel using copious quantities of WW296 powder. I had one fitted onto a 454 Casull FA83 and after 9,000 rounds it looks as new as the day I got it.

[243winxb]

Forcing cones go first. The step in the cylinder photo is where the chamber ends & throat starts. Does show a lot of use. My 29-2 44 mag after factory set the barrel back. Used W296 with 240/250 gr cast for many years.

Needed a new barrel, but this old one is Mag-Na-Ported.

Forcing cone diameter is normally around .020" larger then bullet diameter.
https://www.thehighroad.org/index.php?media/29-2-after-barrel-setback.4114/full

[DougGuy]

Mechanical thing’s dropping off before that would happen yes, but along the way, no erosion. Ok

Doug mentioned about how hard Ruger cylinders are and l was impressed. They buy thier steel already treated and it’s extremely hard. Maybe, if l remember right, that’s one of the reasons why he went to honing instead of reaming.

The temper on those rods that come in on a rail car is all over the map. VERY inconsistent. I know this to be a fact since I can judge how slow a reamer cuts or how long I have to hone to take even .001" out of a throat. SOME cylinders are fairly evenly tempered, and then without reason or explanation the same revolver model, same caliber, has throats on the same cylinder that will ream easier than others, you get around on the other side of the same cylinder and it's like cutting a different metal. BTW, throats where the metal was harder, will finish smaller in diameter than the throats on the other side of the same cylinder. Been there done that a surprising number of times. Enter the Sunnen hone and it's stepless adjustment system, changes in metal temper make it slower to hone, but then the throats come out within .0001" ~ .0002" of each other. Try THAT with a reamer! :shock: You ream enough Ruger big bore cylinders you will know exactly what I am talking about.

Maybe the process the steel mill uses to make the new model medium frame cylinders has changed, they are a boatload more consistent than the older large frame guns.

As far as eroded cylinder throats go, I really have not witnessed this enough to document it. Those chamfers that catch the lead, by the time I get a rotary tool and a tiny stiff stainless brush in the throat to polish out the carbon and residue, I will get it clean enough to see orbital rings on that chamfer, where it was cut with a ragged reamer, and it's just rough as a cob all the way around, but no erosion. you can never get a cylinder with that kind of tool marks to not collect lead there where it's rough.

[243winxb]

https://www.carpentertechnology.com/blog/most-powerful-revolvers-get-lift-from-aerospace-alloys

Ruger Super Redhawk .454 Casull cylinder design- Ruger made a cylinder from Custom 465 stainless, then fired 50 proof rounds from each of six chambers (total 300 rounds) at 92,000 psi.

[DougGuy]

https://www.carpentertechnology.com/blog/most-powerful-revolvers-get-lift-from-aerospace-alloys

Ruger Super Redhawk .454 Casull cylinder design- Ruger made a cylinder from Custom 465 stainless, then fired 50 proof rounds from each of six chambers (total 300 rounds) at 92,000 psi.

Here's a good one for ya, 480 SBH cylinders made of carpenter steel also, not sure it is the 465 alloy, but they machine surprisingly smooth and rather easy. I had a piloted reamer custom ground to remove that abrupt 45 ° step at the end of the chamber and cut a 6 °30' chamfer so it won't ring the chambers with lead.

Here I am with a buckskin wrap around the cylinder, in a fox vise with oak soft sides. It gets hard to turn the reamer the farther down you cut, and the cylinder wants to turn, so I gradually tighten the vise until it quits turning, well, I noticed the pilot got a little stiff and didn't want to go smoothly all the way through the throat, I loosened up the vise JUST a tad bit, and the reamer suddenly went smooth in the throat!

The cylinder was actually egging a bit on the throat that was perpendicular to the wooden jaws, and squeezing on the pilot a bit while the rest of them reamed smooth. That had me saying "hmmmmm" and thinking about it some, so turning the cylinder 90 ° in the vise jaws so the throat that I thought was a little sticky was suddenly free and smooth! And this was a cylinder with throats I had JUST honed to .478" so I know they were smooth and consistent. It was odd to see the elasticity in the carpenter steel, but that's why those guns can take that much power at full throttle loads.

[243winxb]

Saw a report on s&w M19 cylinder expanding on firing. All interesting.

[M-Tecs]

People tend to think that steel is more solid than it really is. Just as the brass expands to the chamber the chamber and barrel expand due to pressure.