The Mechanics of Depositing Jacket Material in a Gun Barrel

"Jacket" material implies a jacketed, lead bullet.

Do you mean "seizing", or "sizing" action?

I'd say that barrel deposits are the result of friction.

Lead bullets, without a gas check, are a different issue.

Not sure I understand the question.

Its called "shaving". I once had a cheap 38 sub nose for my wife and it would shave around 5% of the weight of the bullet. Had to clean the barrel often.

Were you shooting cast bullets and not jacketed?

The engraving process of a projectile rotating band is one of the most basic research aspects in interior ballistics, which has not been thoroughly understood thus far. An understanding of this process is of great importance from the viewpoints of optimal design, manufacturing, use, and maintenance of gun and projectile. In this paper, the interaction of copper and nylon rotating bands with a CrNiMo gun barrel during engraving was studied under quasi-static and dynamic loading conditions. The quasi-static engraving tests were performed on a CSS-88500 electronic universal testing machine (EUTM) and a special gas-gun-based test rig was designed for dynamic impact engraving of the rotating bands. The mechanical behaviors of copper and nylon were investigated under strain rates of 10−3s−1 and 2 × 103 s−1 using an MTS 810 and a split Hopkinson pressure bar (SHPB), respectively. Morphologies of the worn surfaces and cross-sectional microstructures were observed with scanning electron microscope (SEM) and optical microscope (OM). It was found that large deformation and severe friction occur during engraving. The surface layer is condensed and correlated with a hardness gradient along the depth from the top worn surface. The structure of the rotating band and gun bore, band material, and loading rate have great effects on band engraving. The flow stress-strain of the copper strongly depends on the applied strain rate. It is suggested that strain rate and temperature play significant roles in the deformation mechanism of rotating bands... of interest... this abstract..Tribology of rotating band and gun barrel during engraving process under quasi-static and dynamic loading Bin Wu, Jing Zheng, Qing-tao Tian, Zhi-qiang Zou, Xu-hua Yu, Kai-shuan Zhang

If there is a point to your rambling, it may be lost on this forum..

< unsubscribe in indifference.>

I appologise... l will unsubscribe!

You should not let Lyn get up your nose, its all he is good for.....getting up peoples noses, like a cold sore or the flu!!!

He is one of the many uneducated A****Holes we have floating around here......

He is well understood by the many, and ignored completely by the most!!

Stay here, you bring some very interesting knowledge with you, thanks.

I'm not a scientist, just an old retired cop who has been reloading, shooting and cleaning firearms for many years. Any time two metals, one of which is softer than the other rub together, there will usually be some particles from the softer, imparted on the harder one. When this happens at a high velocity such as firing a firearm, along with the heat generated, there will be more. The spinning of the bullet as a result of the rifling in the barrel probably makes this deposit more material.

When we used to fire jacketed .357 magnum ammunition over a long period of time, you could see the deposit of brass and copper on the stainless steel. It appeared copper in color. Firing lead bullets leaves traces and sometimes flakes of lead. The effect is much less noticeable in steel barrels than in stainless steel due to metal color.

There are purist shooters who go fanatical about removing these deposits. However in doing so they probably do more harm than good to the rifling in the barrels. After over 35 years of shooting, the accuracy or function of the firearm does not to seem to have been impaired at all and normal cleaning is all I have ever done to the firearms, and I mean more than a few.

If we all were upset by Lyn, his friends and his abrasive character, there would probably only be a dozen or less people posting on CR4.

I am erring on the high side, just to be friendly to him them!!!

Keep a good sense of equilibrium and simply remember:-

"You don't have to be an Engineer to join and post here, but it certainly improves the quality of the members posts!"

You will very quickly learn who are and who are not!!!

Having a "First" in sarcasm also helps in keeping you sane......But is not a requirement either (to be sane I mean!!), but a strong leathery skin is a must!!

Have a great day and a hearty welcome from all of us here! (Better late than never I always feel!)

Perhaps, due to your online connection problems, you can write your text offline (text file), save it on your PC, and then post the text (copy & paste). If it does not appear, then you have a chance to "re-post" it in full later. That might prevent some simple misunderstandings.

Your choice of course.

Thank you for replying. I give you a GA on two counts. One, because you took the time to answer my diatribe. And I realize I was not overly gentle about it. And, two, because despite your pique at us, you took the time to explain your intent. Thanks again. And welcome to the house.

Thank you for the clarification.

You may find this: Building Muskets of interest, if you've not seen it yet.

Regarding bullet deposits in barrels, much work has been done, with little true success.

This: Teflon-coated bullet - Wikipedia, the free encyclopedia was tried, but as you read the article you will see that they are banned almost everywhere.

While I have been shooting for 50 years, I've done little actual research on metal erosion/deposition during barell flight.

You have already listed most of the mechanisms at play when the bullet travels down the barrell.

Also, not using solid, cast lead bullets will decrease the amount of fouling, but will also increase friction and barrel wear. Barrel wear will likely never be an issue, as WonTon1has indicated.

I have to go off to work now, but look forward to continuing this discussion later.

Welcome to the forum. You will find many, diverse personalities here, most of whom add something of value sometimes.

Cheers.

Actually, Lyn was not inviting you to unsubscribe. That is what he states when he feels like unsubscribing to a thread. It has more to do with Lyn, how the questions were posed, etc., and less to do with you.

You are certainly welcome to stay here, express your opinions about the "engraving" loss of metal from jacketed bullets. I suspect this has more to do with barrel duration than with accuracy of an (automatic) weapon.

Let us take a mental trip back to World War II: The German machine gun mg42, or Maschinengewehr 42, had the most rapid rate of fire of any single barrel gun in WWII.

This gun was well known for having a very hot barrel, and I am pretty sure the Germans used jacketed ammunition. It could be my belief that the rapid build up of heat in this gun was like no other, and they did have to carry many spare barrels into the field, if sustained firing was to be undertaken. At a firing rate of 1,200 and 1,500 rpm, the resulting distinctive muzzle report, was completely terrorizing to the Allies. The sound was more like the sound of heavy canvass ripping, than a train of continuous reports. Rapid cycling of the weapon, sustained bursts, and the effects of the unique (hexagonal) rifling of each barrel all (IMHO) contribute to extra heaving spall deposition in the barrel (which is positive feedback into barrel heating).

Perhaps the nylon parts do not deposit as much in the land/groove transitions of the rifling? At least not until the barrel gets hot. IF you want something that gets so hot that you can eventually "shoot around a corner", there isn't anyone like that here. We here like to keep our rifles shooting straight, our files sharp and not fouled with soft metals like Aluminum, or Brass.

Have you ever tried to file aluminum parts, then switch back to steel? Until you clean that file, you are wasting most of your effort. I view this and the "dulling/softening" of cutting tools due to metal-metal frictional transfer to be well related to the issues of heat and metal depositition in gun barrels. It shows up in both fields during heavy loading on the work piece (or rapid, sustained fire through a gun barrel).

Right.

When I say <unsubscribe> it means I'm leaving.

Barrel length, projectile velocity in the barrel and rifling twist all play a role.

Land and groove height also.

Bullet erosion due to excessive heat/pressure is not so much of an issue with jacketed or gas checked, cast lead bullets.

Gas check - Wikipedia, the free encyclopedia

OldNewby may already know this, and may not care if he shoots only jacketed bullets.

Hi James, thanks for your reply. It certainly caused me to see the opportunity that this aspect lends itself to... the acquiring of accelerated results of continuous similar projectile movement down a barrel under quantifiable constant and changing conditions... thank you

You begin by saying, "depositing of bullet jacket materiall"

then switch to,"projectile rotating band", the only similarity between the two MAY be the materials from which they are made.

You then follow these totally contradictory statements with a barely intelligible string of quasi-coherent sentences, such as, " Morphologies of the worn surfaces and cross-sectional microstructures were observed with scanning electron microscope (SEM) and optical microscope (OM). It was found that large deformation and severe friction occur during engraving"

The last above is particularly profound. "Deformation and friction occur during engraving".

My profound apologies for not paying adequate homage to your scholarly discourse.

Actually it is scholarly discourse; it's copied from the abstract found in the original document:

http://link.springer.com/article/10.1007%2Fs40544-014-0061-3#page-1

I do wonder if OP is one of the authors or a wannabe.

I'd have to think that he's not an author of the paper.

The misuse of terminology (jacket vs rotating band) and the statement, "do the other process steps in the firing sequence also come into play" belies the lack of understanding of the entire process.

Without the "other process steps" the projectile would never traverse down the barrel.

Thus, no engraving and no deposition in the barrel.

WonTon1 pretty much summed it up. When I shot a lot I hardly ever cleaned my forearms. Some guys I know soaked theirs in diesel fuel to "clean" them.

I used to scrub the lead deposits out, before I went to Jacketed bullets.

Finally, reply 4, is a verbatim copy of the abstract of the book you referenced.

Busted!

I still haven't figured out his/her motivation for this posting, but I think I know who it is.

Who do you think it is?

It has the markings of a poster a year ago or so, but I don't want to create any jinx now, dude.

Interestingly and "deep", but probably "over the heads" of many here.....sadly!

Yes! all cast. All i did was to measure the weight of the bullet and then i fired one into a tree and dug it out and measured the weight again. Its surprising how little penetration a snub nose 38 cal has.

Years ago, I did almost the same, but I used an old bath full of (rain) water and a huge piece of sponge to slow it down...

I was not weighing them afterwards, I was simply looking for any deformation due to the gun as it was wildly inaccurate....they were deformed after shooting....

I believe it was a problem with the barrel (its so long ago now!!), barrel replaced or whatever....RN Browning 9mm...

By the way, too shallow an angle to the surface and I am told some (all?) bullets will bounce off the water...

Anyone know if thats true or not? Could be dangerous..... It sounds like an old wives tale to me....

I understand from some Navy Seals to whom I've spoken that the "bounces off water" shibboleth is truth, but that it takes a VERY shallow angle. Barnes Wallace, of WWII Dambuster bomb design fame might have shed some light on this, with his knowledge that a bomb (shape roughly similar to a bullet shape) skips off the water, until spun backwards, at which point it "digs in". I would think it might have a similar effect to spin it laterally, but that the "dig in" would be more to one side, and the effect would be followed by a sudden change in path due to the sudden deceleration of forward and "spinwise" motion, accompanying the "digging in".

It would be an interesting study, but it would certainly require a bigger tank that my backyard would hold in which to test it!

Thanks for your input, that makes very good sense!!

It would take a lake and a VERY calm day maybe to test!! I have the lake only.......

It worried me at the time as I was afraid of a ricochet from the end of the bath. In the end I filled the bath 100% full to reduce the possibility.....it actually never happened in the end.....I aimed at the area of the plughole, where the thick piece of sponge rubber was tethered.

Have you ever cut a bullet out of freezing cold, wet sponge? Its not as fun as it might sound!!! Even just locating the bullet was not that easy.....

For relatively good infos for anyone with regard to the "Bouncing Bomb", there is a good web page here:-

Bouncing_bomb

It actually spins against the direction of movement as you said, whereas a bullet spins at 90° to the direction of movement....

Mythbusters did a good one on ice with bullets and spinning!! But not yet "Bouncing" them on water as far as I am aware!!

But this Guy did!!!

Bouncing Bullets!!

I used to do the bullet bounce trick with a .22 rifle back on the farm where we had a lake carved out of the side of a hill to use as a backstop.

It's an interesting novelty, but not much real use.

Yes its true. Years ago , i was around 10 yrs old, there was a guy shooting at tin cans in the water with a .22 rifle. The bullet deflected and , sadly, killed a young girl about one mile away. They could not figure why she was shot and a ballistics expert did a survey and traced it back to the guy with the .22.

Did they hang him right away, or let him sit and stew in the sun for a few days?

I don't really see this accidont as a hanging offense, but there are judges that might.

All I know is that if hanging was re-introduced for capital offenses, there would be less need for capital punishment. Hangings in the Old West, including Texas were a lot more scarce than many realize, however, there were hanging judges that would just about hang someone for missing the spitoon.

OldNewby, give Lyn a pass. Occasionally he pulls the trigger with Mud in his barrel. ��

Personally, I was hoping your thread topic would get some good input.

LOL!!!

Is the initial depositing of bullet jacket material in the barrel of a firearm purely a seizing action or do the other process steps in the firing sequence also come into play ? Does anybody have any input on this from a metallurgical or tribological viewpoint?
I'm guessing that your question is "How is the bullet (projectile) material deposited on the inner wall of the firearm"?

• Friction
• Heat
• Pressure from the hot gasses
• Debris in the barrel
• Debris on the projectile
• Size mismatch between the barrel and projectile

There are a lot of factors and every firearm is different and will "load" their barrel differently!
Good Luck.

Bryan

Check out the link in #15, it will take you to the original paper that OP plagiarized from, it's an interesting read and gives detailed answers to your questions.

The fascinating thing is that this type of research is even published since it provides information on how to improve the range of the large high energy projectiles that warring countries fire at each other. It would have been stamped "Top Secret" 75 years ago.

I hope this is interesting for you, I just remembered on our RN 4.5" Guns that I looked after in the RN, the cordite was in a brass cylinder/cartridge, but the shell was loaded separately, they were not fixed together.

The cordite in the cartridge was sealed in with a big, screwed in thick "white metal" disk, probably mostly tin, which was vaporised when the gun was fired.

This "metal vapor" cleaned the gun of any debris left behind by the shell.

The cordite fumes coming after, made it dirty again, as did the next shell.

But, no matter how many rounds you had to fire, you only had to clean the barrel of the debris from the last shot at the end of the day!!

Mostly cordite residue.....

This was important for reliability when shooting a lot!!!

The driving bands (copper) on the shell cleaned very deeply as well of course, practically all cordite debris from the previous shot.....

Maybe this could be adapted for smaller ammo when reloading?

hi,

thank you all for your extremely informative and interesting replies. please keep them coming. I will keep you all involved when my research uncovers interesting information relating to this phenomenon and will again ask for input on any new ideas and principles I might find.

Since my last post (linked to this one) I have been wracking my brain over what this "white metal" was exactly.

It had the appearance of "big end" bearing material, as used in bearings for car engines for probably well over 100 years, which is also called "white metal".....

I have tried to imagine it and see if it could be Aluminium, but I really don't think it was....

The best link that possibly mentions it is this one:-

White_metal

But I really don't find it too helpful myself in this area.....

I would expect it to be a mixture that melted at quite low temperatures and therefore easily vaporised.....

I did find that the cap in question is called:-

Case Plug or Mouth Plug - The sealing device in the mouth of a cartridge case used for separate (semi-fixed) ammunition. This may be of cork, plastic or cardboard. The USN originally used a brass mouth cup to seal cartridge cases, but after one "boomeranged" back on board the transport SS Mongolia and killed two nurses in May 1917, cardboard ones were substituted.

Shown in this picture:-

These were found here:-

Weapons_Gun_Data

from experience I can tell you most of the "copper" deposited in the barrel is from friction. I have polished several barrels and the resultant "copper" deposits are much reduced. I have also found that gain twist barrels are more accurate for lead projectiles, especially with heavy for caliber bullets, but not so much for jacked ones.

Would you please provide me with a bit more education on gain twist barrels? Does this mean that the rifling engine has more twist ratio toward the muzzle than the breech?

yes, the twist rate gets faster near the muzzle. Great for helping reduce malformation of softer bullet material.

Manufacturers of firearms list the twist rate, "rate of turn" of the rifling grooves cut into the inside diameter of the barrel. A very common caliber, 30-06, will most often have a rate of "1 in 10" [One turn in 10" of barrel length].

The rifling grooves are easy to see with the muzzle pointed at a light and the breach open. I have never seen a rifle barrel that does not have a consistent twist rate in the rifling grooves.

The rifling grooves are easy to see with the muzzle pointed at a light and the breach open. I have never seen a rifle barrel that does not have a consistent twist rate in the rifling grooves.

Neither have I (though rifling I would not list under my hobbies either!), but it would appear to make sense, to "spin-up" the bullet (somewhat!) slower maybe, especially if only soft lead, so as to prevent it possibly "jumping", as well as probably leaving less metal residue behind, if spun up a little slower...therefore might it be a tiny bit more accurate???

Especially over very long distances.....we are mainly talking about long guns I feel.....

"Thought for the day", maybe one can actually achieve a higher rate of "spin" (assuming that is "good" within reason), with such a method.....

If I remember correctly, "over spun" bullets "tumble" when they hit a body for instance (according to my RN instructor when we were working on an M16!), causing massive damage and shock, for what might be a small caliber. Getting round the Geneva Convention!

I actually have no idea either way, these are just suppositions all on my part......it was a particularly interesting blog, thanks to the OP.

Google is your friend.

In some cases, rifling will have twist rates that increase down the length of the barrel, called a gain twist or progressive twist;

Rifling - Wikipedia, the free encyclopedia

Radical Gain-Twist Barrel for AR and High Power Rifles ...

Thanks for two really excellent links....really informative.

I never realised just how long spinning a bullet has been around!!!

The word "rifle" designated a firearm that had rifling grooves vs the "musket" which was without rifling or a "smooth bore". The spin rate imparted to the projectile as it is forced through the rifled barrel may impart a gyroscopic stability and greatly enhance accuracy through out a longer distance.

I believe a projectile, possibly excluding a ball, that tumbles did not maintain one or more of the factors: rate of spin, velocity, mass or shape that would achieve a maintained gyro' effect. This also is spoken of as "keyhole" from the tear left in a paper target.

We were told in the RN that the M16 military rounds ONLY tumbled ONCE they hit something as the Geneva Convention bans guns/ammo that tumble without ever "touching" anything....as you mentioned with a paper target I believe.....

I submit that a paper target would be unlikely to demonstrate the effect...a second one a few meters behind the first, might!

Whether this was JUST the military version M16 or ammo or not I cannot say.....it was a long time ago. Some people though that it was not a nice way to work.....but being hit by a 7.62 was OK!!

These were bullets, bullet shaped, not "Balls". So they would fly "true", just doing their thing once a say a person got in the way.....

How could you tell if a ball tumbled or not?

Though in the UK military, such ammo boxes are still labelled "Ball" funnily enough - too cheap to buy a new stencil maybe?

See here:-

It appears to define standard ammo!!

Dead people need neither medical care, not evacuation.

That's why FMJ ball ammo was used. It didn't kill the enemy, it just rendered them in need of help. Help=people who are not firing at the enemy.

At least that's what I heard. Never in military, except ROTC in college.

The original M16 rifling was 1 turn in 12 inches. This was not enough to stabilize the standard NATO bullet at longer distances. You would actually get "keyholes" on paper at over 100 meters from bullets starting to tumble. The new spec is for faster twisting rifling of 1 turn in 10 or less inches. Some match bullets go 90 grams vs the 55 gram originals. These heavy for caliber bullets need a faster twist rate like 1 turn in 6.5 inches to stabilize. This is where gain twist barrels come in. Light jacketed heavy for caliber bullets get damaged by instant fast twists. Long range shooters who like these heavy for caliber bullets are the ones driving the gain twist Renaissance.