is solvent a lubricant? then why the bore guide?

[clcustom1911]

From This Accurate Shooter Article

Bullet RPM = MV x (12/twist rate in inches) x 60

For a 8 twist barrel it would look like:

MV x (12/8) x 60 = RPM


When you work the math you'll see your spin is Waaaayyyyy faster than 3600 RPM, but your head is in the right spot. Good work and thinking.

 

[Walter Haas]

Bullet RPM = MV x (12/twist rate in inches) x 60

For a 8 twist barrel it would look like:

MV x (12/8) x 60 = RPM

Thank you! You're right, I wrote RPM when I should have written RPS. So its even more insane than I was saying. The bullet is going from 0 rpm to 216,000 rpm in 1.3ms! That is super high moment of inertia for two soft and heavy metals. The metals are definitely wanting to "smear" in a radial pattern and how the copper doesn't slip over the lead I don't know, it would be interesting to find out. Maybe the pressure behind the bullet opposes the slipping forces. I would also like to know how close to being a liquid the two metals are on their way out of the barrel. Lead melts at 621 degrees F, and copper at almost 2000F and maybe that's the answer right there. The lead core liquefies from the heat and the bullet spins freely around it. This is too much I'm going to bed.

 

[clcustom1911]

Thank you! You're right, I wrote RPM when I should have written RPS. So its even more insane than I was saying. The bullet is going from 0 rpm to 216,000 rpm in 1.3ms! That is super high moment of inertia for two soft and heavy metals. The metals are definitely wanting to "smear" in a radial pattern and how the copper doesn't slip over the lead I don't know, it would be interesting to find out. Maybe the pressure behind the bullet opposes the slipping forces. I would also like to know how close to being a liquid the two metals are on their way out of the barrel. Lead melts at 621 degrees F, and copper at almost 2000F and maybe that's the answer right there. The lead core liquefies from the heat and the bullet spins freely around it. This is too much I'm going to bed.

I dont think the metals have enough time exposure to that heat in the barrel to get to their melting temps....... you can quickly stick your fingers in boiling water and pull them out as fast as you can. Warm? Absolutely, did you sustain burns? Likely not.

 

[Walter Haas]

I dont think the metals have enough time exposure to that heat in the barrel to get to their melting temps....... you can quickly stick your fingers in boiling water and pull them out as fast as you can. Warm? Absolutely, did you sustain burns? Likely not.

why do your car tires get hot when the road is not hot? Kinetic energy transforms into elastic energy which transforms into heat
as a byproduct. The mechanical deformation of the bullet heats it up without even considering that copper is the best thermal conductor there is. copper is conducting super high heat at the same time the bullet is being squashed in just like the road is pushing your tire in. If the melting point of lead is 621 Fahrenheit it wouldn’t surprise me if it’s liquefied at least in spots like near the boundary of the copper.

 

[DJL2]

what happens if there’s a lot of oil in the bore and you forgot to run a dry patch and then you fired the rifle? my guess is the bullet would hydroplane over the oil and then the heat would burn the oil leaving more fouling than you would have had. or if there’s enough force between the copper jacket and the bore it could shove all the oil out but that seems less likely because that oil has a strong adhesion quality, it clings

No. The bullet cannot hydroplane over anything because it's being compressed into the bore in the first place - there's nowhere for it to go. When people talk "engraving force" this is what they are referring to. When a bullet enters the rifling, the bore of the rifle compresses the bullet at the lands - this causes localized yield/plastic deformation which is easily seen on a fired bullet.* If the bullet encounters more fluid than can be pushed into the void left between the bullet and the rifling grooves, there IS going to be a problem. Worst case, because fluids are essentially incomprehensible, a significant increase in friction/pressure causes your barrel to yield - i.e. fail through plastic deformation. Best case, excess oil is expelled from the bore with minimal pressure/velocity fluctuations and no deformation of the projectile.

Light coat of oil = no big deal, shoot over and be happy. Heavy oil = rolling the dice, hopefully not ruining your barrel.

*Note: this is the reason the solid metal bullets typically use "driving bands." The additional resistance of a solid metal bullet design can result in significantly higher pressures.

ETA: Review the above. If there is 50,000 psi engraving the rifling into the bullet, you can appreciate that for the jacket and core to rotate past one another they would need to overcome the friction created by that 50 ksi and it would stop upon the jacket being mechanically locked to the core via the engraving process. Ultimately, while academically interesting, I'm not sure this line of discussion is actually going to help you.

If you have time, read this:

http://2poqx8tjzgi65olp24je4x4n-wpengine.netdna-ssl.com/wp-content/uploads/2012/07/understanding-and-predicting-gun-barrel-erosion.pdf

 

[Walter Haas]

No. The bullet cannot hydroplane over anything because it's being compressed into the bore in the first place - there's nowhere for it to go. When people talk "engraving force" this is what they are referring to. When a bullet enters the rifling, the bore of the rifle compresses the bullet at the lands - this causes localized yield/plastic deformation which is easily seen on a fired bullet.* If the bullet encounters more fluid than can be pushed into the void left between the bullet and the rifling grooves, there IS going to be a problem. Worst case, because fluids are essentially incomprehensible, a significant increase in friction/pressure causes your barrel to yield - i.e. fail through plastic deformation. Best case, excess oil is expelled from the bore with minimal pressure/velocity fluctuations and no deformation of the projectile.

Light coat of oil = no big deal, shoot over and be happy. Heavy oil = rolling the dice, hopefully not ruining your barrel.

*Note: this is the reason the solid metal bullets typically use "driving bands." The additional resistance of a solid metal bullet design can result in significantly higher pressures.

ETA: Review the above. If there is 50,000 psi engraving the rifling into the bullet, you can appreciate that for the jacket and core to rotate past one another they would need to overcome the friction created by that 50 ksi and it would stop upon the jacket being mechanically locked to the core via the engraving process. Ultimately, while academically interesting, I'm not sure this line of discussion is actually going to help you.

If you have time, read this:

http://2poqx8tjzgi65olp24je4x4n-wpengine.netdna-ssl.com/wp-content/uploads/2012/07/understanding-and-predicting-gun-barrel-erosion.pdf

Sounds like “engraving “ damage depends on the elasticity of the barrel but I think you just talked me into running a dry patch through before shooting.

 

[DJL2]

You're a curious type - I'd recommend you get out there and do some reading on Optimal Charge Weight (OCW). The idea that underlies OCW load workup is that when you ignite a cartridge, you get different types of barrel deformation (all elastic, mind you).

There is the commonly referred to "barrel whip" which is what we conceptualize as a wave propagating from chamber to muzzle that causes the muzzle to occupy a slightly different position from shot to shot. The amplitude of oscillation is cited as a common reason to run a heavier (or shorter) barrel for accuracy (or at least it used to be before heat dissipation, spotting your impacts and a host of other things came into discussion).

However, OCW focuses on a different type of oscillation - essentially the barrel moving radially outwards from the center line of the bore. The idea being that this wave moves back and forth between chamber and muzzle and changes the shape and size of the bore during the bullet's travel. OCW seeks "nodes" where the muzzle is at its minimum during the bullet's exit. Regardless of whether you buy into the methodology of OCW load development, the mechanics discussion would interest you.

 

[2aBaC̶a̶]

Anything you have in your barrel is going to be like a speed bump in a tunnel. If it doesnt blow out it will imprint on your bullet and creat excessive pressure on the barrel.

So yeah, just enough oil to keep rust and patina from forming on the surface.

 

[Walter Haas]

You're a curious type - I'd recommend you get out there and do some reading on Optimal Charge Weight (OCW). The idea that underlies OCW load workup is that when you ignite a cartridge, you get different types of barrel deformation (all elastic, mind you).

There is the commonly referred to "barrel whip" which is what we conceptualize as a wave propagating from chamber to muzzle that causes the muzzle to occupy a slightly different position from shot to shot. The amplitude of oscillation is cited as a common reason to run a heavier (or shorter) barrel for accuracy (or at least it used to be before heat dissipation, spotting your impacts and a host of other things came into discussion).

However, OCW focuses on a different type of oscillation - essentially the barrel moving radially outwards from the center line of the bore. The idea being that this wave moves back and forth between chamber and muzzle and changes the shape and size of the bore during the bullet's travel. OCW seeks "nodes" where the muzzle is at its minimum during the bullet's exit. Regardless of whether you buy into the methodology of OCW load development, the mechanics discussion would interest you.

That’s interesting, thank you.

 

[spife7980]

guys, you see this patch third from the left? It almost seems to say that the groove or I should say the four grooves are very wide. Why would they design the barrel like that? I mean only four of eight edges matter, right? each trench has two edges but only one edge is experiencing heavy force spinning the round.
I wonder if on some of these copper jacketed bullets with a lead core these trenches spin the copper around the lead. maybe some manufacturers don’t realize that’s happening.

If you want a modern bullet to shoot worth a damn its got to spin to stay stable in anything other than a perfectly spherical ball.
If you want it to spin you have to induce some mechanism of rotation. To rotate it you basically have to put some pressure on it from one direction. When the bullet is being pushed forward down the barrel its running into the lands which are pushed into one side as you said and if we consult newtons laws of motion: for each reaction there is an opposite. The right side of the rifling pushes on the left side of the bullet so it forces it to spin to the right.


The bore is drilled to.300", the grooves are then cut to remove that material out to .308". A bullet is .308". The bullet is basically an exact fit to the widest part of the barrel (so zero room to hydroplane lol) and the groove cuts into the jacket .004" on each side (3% of its diameter only). Thats enough for the press fit to hold onto the bullet and spin it but not enough to really disturb the bullets internals. If the lands were much wider you would have that much more displacement of bullet material.

And those exterior grooves dont really effect or drag on the bullet in flight as the bearing surface it is in a laminar flow area and it just sort of glides smoothly past. A cannelure that cuts across the bullet instead of along it length causes a disturbance.

You noticed that the lands are small, what happens if instead of a 4 groove barrel you had a 5 groove or a 6 groove or a 3 groove, the proportion of the lands to the grooves with respect to the total surface area has to change. A 2 land barrel will have much wider grooves and lands than a 5 groove will but the total surface area of each should roughly total up to about the same.

Then you have the actual geometry of the individual lands; polygonal that was shared, you can also have a 5r

Or anything else thoughout history!

That said, when the lead core is swaged into the copper jacket its really freaking forced in there and its solid. If the bullet was created evenly and the barrel is even through out its length as it should be than any disturbance should be evenly applied to the bullet so even if it did swirl inside a smidge (which it doesnt) it should still result in an even result.

It will take much longer than the milisecond the bullet is exposed to the burning powder to get it up to temp. If it didnt then how in the world would any of these plastic tipped bullets ever work?



And a bullet 1) doesnt have room to hyrdoplane over fluids as there is zero space for it to do so and 2) if there are noncompressable liquids they would either instantly be turning into gases ahead of the bullet or they would stay in the bore and expand it to force room which is why its never a good idea to shoot with a wet bore.

Also, I highly doubt your patches will ever come out clean, once they stop coming out filthy you are clean.

So to sum up, after a hundred something years... the bullet and barrel manufactures have a pretty good handle on what they are doing and your concerns were addressed long before any of us were alive lol

 

[I SHOOT]

LmAO

WTF

 

[Walter Haas]

If you want a modern bullet to shoot worth a damn its got to spin to stay stable in anything other than a perfectly spherical ball.
If you want it to spin you have to induce some mechanism of rotation. To rotate it you basically have to put some pressure on it from one direction. When the bullet is being pushed forward down the barrel its running into the lands which are pushed into one side as you said and if we consult newtons laws of motion: for each reaction there is an opposite. The right side of the rifling pushes on the left side of the bullet so it forces it to spin to the right.


The bore is drilled to.300", the grooves are then cut to remove that material out to .308". A bullet is .308". The bullet is basically an exact fit to the widest part of the barrel (so zero room to hydroplane lol) and the groove cuts into the jacket .004" on each side (3% of its diameter only). Thats enough for the press fit to hold onto the bullet and spin it but not enough to really disturb the bullets internals. If the lands were much wider you would have that much more displacement of bullet material.

View attachment 7271647


View attachment 7271651

And those exterior grooves dont really effect or drag on the bullet in flight as the bearing surface it is in a laminar flow area and it just sort of glides smoothly past. A cannelure that cuts across the bullet instead of along it length causes a disturbance.
View attachment 7271653



You noticed that the lands are small, what happens if instead of a 4 groove barrel you had a 5 groove or a 6 groove or a 3 groove, the proportion of the lands to the grooves with respect to the total surface area has to change. A 2 land barrel will have much wider grooves and lands than a 5 groove will but the total surface area of each should roughly total up to about the same.

Then you have the actual geometry of the individual lands; polygonal that was shared, you can also have a 5r
View attachment 7271658

Or anything else thoughout history!
View attachment 7271659
View attachment 7271660
View attachment 7271661



That said, when the lead core is swaged into the copper jacket its really freaking forced in there and its solid. If the bullet was created evenly and the barrel is even through out its length as it should be than any disturbance should be evenly applied to the bullet so even if it did swirl inside a smidge (which it doesnt) it should still result in an even result.

It will take much longer than the milisecond the bullet is exposed to the burning powder to get it up to temp. If it didnt then how in the world would any of these plastic tipped bullets ever work?



And a bullet 1) doesnt have room to hyrdoplane over fluids as there is zero space for it to do so and 2) if there are noncompressable liquids they would either instantly be turning into gases ahead of the bullet or they would stay in the bore and expand it to force room which is why its never a good idea to shoot with a wet bore.

Also, I highly doubt your patches will ever come out clean, once they stop coming out filthy you are clean.

So to sum up, after a hundred something years... the bullet and barrel manufactures have a pretty good handle on what they are doing and your concerns were addressed long before any of us were alive lol

That's fantastic! That's the most amazing technical answer I think I ever got on the Hide. I see and I get it. Lots of interesting points I didn't see before. I've shot on a wet bore about 5 times, I think. Wish I hadn't done that. I'm shooting a Steyr SSG08A1, does that barrel tell you anything? I'm so far behind the crowd here I know my questions are a weird combination of smart and dumb. I need time to digest what you wrote but, bravo, sir! Thank you!

 

[spife7980]

You’ll be fine, barrels can take a few beatings. It takes A LOT to actually physically displace material. Oil you bore or whatever, just run one dry patch last to pick up any stray puddles.

 

[b6graham]

Bartlein says clean lightly every 100 rounds, so that is what I do. Boretech seems like a good solvent and it can be used to store the firearm.

just no. no.no. no.

 

[b6graham]

That's fantastic! That's the most amazing technical answer I think I ever got on the Hide. I see and I get it. Lots of interesting points I didn't see before. I've shot on a wet bore about 5 times, I think. Wish I hadn't done that. I'm shooting a Steyr SSG08A1, does that barrel tell you anything? I'm so far behind the crowd here I know my questions are a weird combination of smart and dumb. I need time to digest what you wrote but, bravo, sir! Thank you!

no they're just dumb. there is zero smart in any of your questions. over complicated. and you bring out the biggest morons to comment

you bought a shit gun and could have had an AI. the barrel tells us nothing. legit nothing. but stop cleaning it

you're seriously the best Hide troll of the last several years. congrats mate

 

[308pirate]

I'm not doubting their engineering...…….. My guess is the copper and lead both are being smeared in a spiral pattern but to what extent I don't know.

Yes Walter, yes you are.

There are quite a few of us here who have the technical education, professional experience, and mental capacity to delve into such investigations.

But we don't. Geeking out on what happens to the boundary between the copper jacket and the rifling or between the jacket and lead core isn't going to help you in anything you do even if you think it will help or think it's interesting.

We spend our time wisely, not pondering useless minutia that's actually way outside of our lane no matter how smart or educated we are and instead spending that time behind the rifle learning what really matters.

I suggest you do the same.

 

[308pirate]

Sounds like “engraving “ damage depends on the elasticity of the barrel

WTF...…….

The barrel's "elasticity" is irrelevant when the yield strength of copper and lead are so dramatically lower than that of any steel barrels are made of.