Why is there no coatings used in rifle throats to slow erosion?

[Loner]

I had a crankshaft built up and nitrided back in the 80's. It was around long before that
I am sure. I can't see how it could do anything but improve a barrel. It makes it smoother
tougher, more heat resistant and more abrasion resistant. I won't buy the "last longer
than chrome lined barrels" claims I've seen made but I wouldn't doubt it would double
the throat life on the big over bores. And the claimed higher bullet speeds also make sense to me.

 

[royinidaho]

fly,

Read the whole thing. Good stuff.

I noted this tidbit from the report: "This shows that erosion resulting from the propellant gas is larger in the free flight zone compared with the center zone. This result seems natural since the pressure in the free flight zone is about double that of the center zone."

I wonder how much of this erosion is due to hot gasses or friction from powder kernels?

This finding suggests that the boys at the Ogen Depot, back in the day, were on the right track. I don't know what their objective was. I understand that their development remains in use in the 10x(5?) mm cannon shell.

Their work was with "forward ignition". Kirby did some experimenting with FI. I've ruined a few pieces of brass messing with it also. Actually not ruined, if I sleeve the drilled and threaded flash holes.

My idea is to burn all the powder in the case. I doubt that is a possibility. After launching a few flash tubes down range barrel temperature profile definitely was affected.

Objective:

• Reduce throat erosion. That is, the portion of throat erosion due to sand blasting effect of unburned powder kernels under high pressure.

Results:

• Recoil noticeably reduced
• Barrel temperature beyond the first 6 or 7 inches was lower than the chamber area.
• Barrel heat flowed from the chamber area down the barrel.
• Group size decreased (consistently but from an already great shooting hunting rig not enough to be worth the effort for group size reduction only.

Conclusions:

• RUM sized cases are too small to benefit from forward ignition. (We'll see about the 375 AM cartridge.lightbulb)
• Sufficient ballistic performance, for hunting, will have to be limited to realistic chamber pressures. The best I could determine was that flash tube launches occurred only at extreme velocity/pressure which from close observation of threads in the primer pocket seemed to indicated case head expansion released the flash tube. No sheared brass was detected in flash hole threads. Threads were good and reusable throughout the experiments. (Have no idea of where the flash tubes landed. )
• Reloading process was extended. Add flash tube removal and installation after primer removal. Not much of an effort but definitely an extra step.

Will I do additional testing. Oh, yeah!



Also, after about a dozen Upper GI roto-rooter procedures, its the throat that takes the beating.

 

[elkaholic]

That's pretty good stuff Roy! Let us know if you kill anything with those flash tubes...Rich

 

[theflyonthewall]

RIGHT ON roy!!!

I had thought about changing the ignition curve, but dismissed it too soon. My only idea on that subject was a ridiculously hot primer to attempt to drive a flame front THROUGH the powder column. Once I realized that no one in the world would likely be willing to create such a primer for some "joe-nobody" like me to play with, I let it go.

But your flash tube idea could be pure gold. If you'd rather answer me in PM's due to intellectual property type issues that's perfectly ok with me, but I have to ask---were/are your flash tubes drilled along their length to allow flame propagation to initiate in the very rear of the case (as with normal ignition) and THEN also to move the flame front to a more forward position as well?

That's a bit hard to read and actually two questions in one. Basically I'm asking how your controlling the flow of ignition with the flash tubes. Is the main purpose of the flash tubes to simply initiate ignition in a more forward position, or does the design allow for greater control than that?-----perhaps ensuring a more complete burn in a shorter span of time?


Roy, you've got me fired up now....lol. There's a great deal of potential in your work with the tubes and in different powders. PLEEEEEASE throw me a few more morsels of info when you get time. I LOVE discussing technical schtuff like this!

 

[royinidaho]

fly,

Intellectual property? That's funny. Especially to an Italian.

There are tons of patents out there. All way to complex to be sensible. I doubt any have been tried.

Two noted shooters back in the day, can't recall their names, but on the order of Keith, Ackley, etc., did work at Ogden Utah, now Hill Air Force Base.

I started with the 338 RUM then moved to the 270 Allen Mag.

First step was to drill the flash hole. Then tap it. Attempted to keep all things straight.

Next was to cut the flash tube to length. Length was to have the tube end about 1/8" below the seated bullet.

I then cut notches in the tube front end to seat the tube with a flat blade screw driver.

There were no holes along the tube. I wanted ignition to initiate at the base of the bullet.

Hang fires came with too much empty space behind the bullet. I was a bit sensitive to what may happen with a full charge considering apparent load density change due to volume of the tube.

Powder used was US-869 with some unwarranted concern for powder dropping down the tube. Turned out to be a non- apparent problem.

Improvements:

• Using pipe thread on the tube end results in a tapered thread. Thus the first couple of threads are shallow. This wouldn't seem to have sufficient thread to hold.
• Tighten the tube against a flat surface as the way a muzzle brake is indexed.

I used super glue, devcon, metal putty etc., none of which worked.


When the tubes remained after the shot, as much as a 1/2 turn was necessary to tighten them.


Oh, another thing that I neglected to mention was that the drop in ES nearly brought tears to my eyes.


You now have all of my information.


I'm figuring that if a hint of possible success is let loose around this outfit some one will pick it up and run to the next level. Then maybe someday . . .

 

[elkaholic]

Looks like you've made a darn good start Roy! By the way, I stopped in a restaurant just off the freeway in Blackfoot last week and the Waitress didn't know you. Whats up with that?? Looks like you need to do a little PR work......rich

 

[royinidaho]

Rich,

I bet she know or knows of at least one of my 7 kids.

 

[elkaholic]

Rich,

I bet she know or knows of at least one of my 7 kids.

Probably so! I couldn't remember your last name but told it was "Capone" or something like that

 

[royinidaho]

links to referse/forward/frontal cartridge ignition.

Reverse Ignition Cartridge

fronal ignition [Archive] - Benchrest Central Forums

Front ignition in cartridges... - Page 2 - Saubier.com

International Ammunition Association {iaaforum.org} - View topic - .303 Olympic Match cartridge


flyonthewall,

Think about it a bit. Here I am, a fella with a 408 CT case, based on, I think, a 505 Gibbs, necked down to 375. The motivating part is the lace of case availability.

Jamison went TO, Chey Tac is proprietary, and I have only 99 cases at something like 4 bucks a piece. Hmmm, 400 bucks for brass. If I get 5 loads each figure how many years those are good for with my tendency to shoot a more than I should.

If I load down, they last longer but I no longer am shooting and extreme magnum. Just really big magnum.

What if . . . the taboo on use of steel cartridges were over come. What if . . . something like that british cartridge in one of the above links were made just right.

They were machined instead of pressed. Hmmmm, probably costly.

If I had 25 loaded cartridges with cases that would last forever, and required no resizing and would hold a primer, or even used electric ignition, I think I'd go for that. Hell, I'd jump all over it.

$625.00 for 25 of eternal cartridges would be a deal.

Not much of an economic analysis. Like I said, intelligence isn't my strongest suit.

 

[theflyonthewall]

Great links, roy!! I have a much better grasp on it now.

Some random thoughts:

To my way of thinking, the reason that frontal ignition hasn't seen the success that it has the potential to, is the SOURCE of the ignition-----the primer. I don't have proof, but I can't possibly believe that with a length of travel of the flame front in a case the size of yours (case length) that a single point, primer-type ignition can reliably ignite a powder charge from one end to the other before the bullet began traveling forward and changing the pressures in the case.

If my thinking is correct, the "yet-unburned" powder that remains in the case is likely going to be pushed from the case to the barrel no matter which end is used to begin the burn. Maybe I'm wrong here, but I'm basing this on the belief that the pressure rise will travel a good deal faster than the flame front will. Therefore the pressure sends unburned powder down the tube despite a great deal of effort to keep it from doing just that.

So what I'm thinking has to happen is a new ignition system needs to be found, that we can retrofit into your cases.

And that's about where my brain leaves off tonight....lol. I'll be tossing some concepts around and let you know if I find something that seems worth looking into.

 

[theflyonthewall]

Hey Roy, check your PM's. I think I just tore the lid off of this problem, so to speak.

 

[royinidaho]

I'll check PMs.

My flash tubes ended at the rear of the shoulder.

I used nothing but Fed 215 magnum primers. Not the GMs. Kirby says they are the hottest.

Ignition began at the base of the bullet.

Don't know where it went from there.

I doubt that no powder movement occurred. The process seems to be a huge volume expansion rather than a flow of gases. Of course, the gas behind the bullet flows to the muzzle, as does the remaining gas. But at a different rate.

There's a lot to think about.

I know of no analysis codes that show dynamics of the process.

 

[philip140]

Don't know if anybody else has said this already, but FN Chrome line the bore of their rifles for longer service life and they're one of the few companies out there that guarantee 1/2moa or less accuracy

FN A3 G Rifle

Phil

 

[theflyonthewall]

Thanks for the link, phil!

Is the chrome lining in the bore only? Do you know if the chrome lining is continued into the throat area? Or is it "just" in the bore from the beginning of the rifling to the muzzle?