High Velocity Throat Erosion

Philward said:
Maybe:
  • barrels need better metallurgy, create a steel that will not firecheck etc.
  • propel projectiles with something other than a burning propellant to see if the same barrel wear result. (not sure how to create 60k psi)
Click to expand...
Nitronic 60 perhaps?

As far as a heatless pressure source….. harbor freight air compressor should do it 😉

My take away from this…….
Some where down the road I will order a barrel manufactured by steve that will propel a 151 AH at 5000fps for my RUM.

I already have the projectiles on hand, hurry up with the barrel technology steve.
 
jessej said:
Nitronic 60 perhaps?

As far as a heatless pressure source….. harbor freight air compressor should do it 😉

My take away from this…….
Some where down the road I will order a barrel manufactured by steve that will propel a 151 AH at 5000fps for my RUM.

I already have the projectiles on hand, hurry up with the barrel technology steve.
Click to expand...
As I read this I was thinking I would volunteer bullets for testing when you get the barrel. I guess that's it of the question, now I gotta come up with a barrel. I'm thinking smooth bore. No lands to wear out and very low engraving pressure!
 
RockyMtnMT said:
As I read this I was thinking I would volunteer bullets for testing when you get the barrel. I guess that's it of the question, now I gotta come up with a barrel. I'm thinking smooth bore. No lands to wear out and very low engraving pressure!
Click to expand...
So you gonna start turning the "grooves" the other way? Spiral fluted bullets? 😜
 
Franklin Armory developed an AR15 with straight rifling and it keyholes like hell so I guess these bullets are supposed to fix that. It's been almost 5 years now and I don't see any production ammo available though.
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mcdil said:
Thank you for this link. I've been keeping up with this thread and find it interesting to see all the theories and test data many of you have witnessed. In the software calculation, playing with the numbers and the moly on or off leads me to what I theorize, but have no test data to support, that reduced barrel friction by the bullet will increase barrel life. The only way to get to the same peak chamber pressure, with a lower friction bullet of the same weight, is to increase its acceleration. Moly and HBN do this as do certain designs that reduce friction by nature. Our bullets do this, as does the OPs. Curious as to how that plays out overall, as barrel erosion isn't a function of just one variable, but rather an interaction between a serious of variables, probably not linear as well, making any test analysis very difficult to wrap a design of experiments around to actually understand all the puts and takes and how they interact.

If I give it my best go, I do think it's a sum of kinetic energy dumped into the barrel and displaced over the surface area of the barrel when the fire cracking phenomenon is an issue. A larger diameter caliber obviously has more surface area, which distributes the load over a much larger area. At some point, whatever that is, the fire cracking phenomenon falls below a critical threshold, hence why we don't see it further down the bore. That's probably a function of a chemical and mechanical reaction, combined. Back to the kinetic energy above; a lower friction bullet has more of that energy physically imparted into it as a function of acceleration rather than the barrel as a function of friction, hence the theorized life improvement due to less energy put in the barrel, especially the first part of the engraving process.
Click to expand...
A very interesting thread.
As a note: we have a .416 barrel that had not been cleaned on a regular basis. In fact it was so "dirty" that for 12+" the lands were fully filled and the only way you could detect them was the corrosion event. Upon cleaning the barrel- a few days and 80patches- the bore showed fire cracking for 18" plus. This barrel had 500 rounds in it. IF the grooves are packed/dirty/filled - just what are we engraving? Or are we sending a "button" down the barrel? Something has to give and the "friction heat" probably approaches a welding event.
Our 260Rem has light fire cracking for about 1" with 1500 rounds through it - a gas gun.
Inversely we have a .460barrel with the same round count- immaculately taken care of- and the fire cracking is only a few inches in length.
Our 260Rem has light fire cracking for about 1" with 1500 rounds through it - a gas gun.
We have some barrels in which the "fire cracking" appears to have lifted off leaving a "oatmeal" like structure behind. I have seen this phenomena in another field of work and could be replicated quite easily - MEMS, super smooth finishes (Single digit Angstrom level). We could reproduce this "finish" up into the single digit micron values. Testing to see if the fire cracking lifted or it is bad material is another problem, but it sure is not helping things concerning the "accuracy" formula.
We are running a series test of materials attempting to directly replicate the fire cracking and isolate the individual variables. To the point of material- 416 is not a heat resistant material. It should also be noted, that outside of powdered metals, you can have large differences in a single bar of material resulting in a barrel being different than the immediate barrel following on the same stick. "Large" being how big of a "microscope" do you view the parameters with. We are testing materials with 3x the heat resistance- however like all engineering attempts "compromise" is the gorilla in the room.
The large gain twist- in our opinion works.... and works very well.
 
In the past, I spent a little time at the test site, and was responsible for furnishing materials that I can't even pronounce, for engine development and testing. The kind of engines that shake ground and make it rain.
I am confident, we can build a barrel that will still look and perform like new after 10k rounds.
I am not confident, that any of us could or would pay for it.
 
You would need a new reamer made from something even harder to chamber it. Then hope it cuts smooth enough not to chatter it up. Makes me think a new process similar to nitriding that makes the surface of the metal harder and smoother might be a more cost effective route.
Just thinking out loud, and enjoying the brainstorming.
 

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