Myths of the gas check

[rhead]

When a small piece of led is removed from the bullet by gas cutting it will be surrounded by the hot gasses and no longer protected by the realitively massive heat sink of the bullet. In this enviroment it may have time to melt into a microscopic droplelt or maybe a nearly melted particle. If this particle inpacts something and stops (the inside of th barrel or a fixed bayonet) its kinetic energy will be released as heat and leave a small droplet waiting to get ironed onto the barrel by the passing bullet. The melmay be occuring after the leat is removed from the bullet.

[Bass Ackward]

ROTFLMAO

Two shooters standing on a street corner theorizing.

First one is discussing an issue and is therefore theorizing. The second guy is theorizing if he is wright or wrong.

Makes shooting sort of like politics if you think about it.

[Newtire]

Boobacious. She is a very boobacious lady. Everybody gets the meaning---a good word.

Carpetman, it is "Boobalacious" to be correct. "He admired the boobalaciosity of the lady." (or here in California-could be a guy also)

[44man]

When a small piece of led is removed from the bullet by gas cutting it will be surrounded by the hot gasses and no longer protected by the realitively massive heat sink of the bullet. In this enviroment it may have time to melt into a microscopic droplelt or maybe a nearly melted particle. If this particle inpacts something and stops (the inside of th barrel or a fixed bayonet) its kinetic energy will be released as heat and leave a small droplet waiting to get ironed onto the barrel by the passing bullet. The melmay be occuring after the leat is removed from the bullet.

Now this is something I never thought about. Tiny droplets could very well be melted. But how would it stick is the question? If a fouled barrel was sectioned and you used a soldering iron, I don't see any way you would get solder to stick without going to bare, clean steel first and using a good flux. Even the wrong flux or using a flame on the wrong flux thats burns will prevent soldering.
I have been soldering for 60 years, started as a kid making toys and yes, the metal must be super clean and HOT before anything sticks. Metal must be at least to the melting temperature of the solder. If cold, a piece of lead might stick but you can pop it loose and any part that is soldered onto cold metal will fall apart.
Leading a barrel by soldering melted lead into it would be like soldering copper pipe together using a light bulb for heat.
I know a lot of you have tried to do plumbing when there was some water in the system! Even one drop turning to steam will stop you short.
I have soldered sights on and removed soldered parts from military rifles and I can tell you that you will not touch the metal.

Now there is something else going on and you can see it with a boolit mold if you cut a soft sprue. Lead will stick to the plate and top of the mold even though neither is hot enough to solder nor is the lead molten. In fact if you really wanted to solder on a mold block it needs to be much hotter and clean with a good flux used.
So maybe we should look at barrel leading the same way we look at the top of our molds.
Could it be called "mechanical" soldering? Do the droplets forced from the sides of an undersize boolit just get mechanically force soldered to the steel?
OK, we use Bullplate to prevent the problem with a mold. Seems to me the boolit lube is doing the same thing in the bore and is why a wax coating alone on a boolit will work, providing a barrier against "force" soldering.
How about the lead on the bayonet! I picture the end of the muzzle acting just like a cylinder gap at the instant the boolit exits, blowing gas pressure and any lead droplets/pieces sideways to impact the steel bayonet.
Does this lead really have to be melted to stick to the steel????
Anyway, I think everyone is looking at it all wrong, thinking it is HEAT soldering and the lead is molten and the steel hot enough to solder.
Have I got you thinking yet?
I think Rhead is correct in describing what happens but I have my doubts that the lead is molten, but who knows?

[looseprojectile]

I have read all the posts in this thread a couple of times and I think I have learned something. Very entertaining.
Most of the posters have some good points and should be given some consideration.
I conclude that the simple presence of "FRICTION" causes leading. Reduce friction with lube or alloy and no, or reduced friction and leading occurs.
Now someone splain how making the boolit fit tighter in the grooves results in less leading, or friction. Maybe a combination of lube, less gas cutting and such?
Many of you arent old enough to remember when the gummint would allow we the people to keep and bear, "strike anywhere" matches. These matches could be struck [using their term],on the seat of your Levi's. By rubbing these matches briskly on just about any surface they would get hot and ignite from the FRICTION.
Shucks, just rub a knuckle on your pants really fast and you will get the picture.
Friction causes heat. The more pressure and speed that is applied the more HEAT.
Absoutely "INSTANT" heat.
Gots my asbestos suit on.
Life is good

[44man]

Yes, but would your hot knuckles melt a boolit? I have picked up thousands of boolits and I can't find any sign of melting. I HAVE seen too small of a boolit etched by gas.
If the surface was turning molten the boolit would never take the rifling. Remember the barrel friction is so short in time that nothing really happens. The mass of the barrel sucks up the heat. Shoot a high power rifle fast and pick up a case, it is hot but but it won't burn your hand or melt lead.
I don't know if any of you have shot dead soft .38 wadcutters much. But they would pack a bore full of lead and the rifling would not be seen anymore. The outside of the cylinder would also be packed with lead. And yet guys here shoot lead to over 2000 fps in rifles with no problems.
You have to admit something else is going on other then melting and I still say it is impact and roll over soldering.
Then there is the really funny thing. Shoot a steel plate with a high velocity cast boolit and the boolit explodes but there is no soldered lead on the plate???? Just a splash. In a few days the crater will be all rusty. Why didn't lead solder the surface and protect it from rust? Why didn't the extreme heat transfer solder the steel?
Hey, I am getting a headache!
I forgot to add that the compound in the matches was very sensitive and also had an abrasive cast into it. If you remember, just a slow rub on a rough surface would light them. Very little friction heat needed.

[leftiye]

Lloyd - Gawd! And I'm a past master of the run on sentence. Kudos, man!

[looseprojectile]

a lot like skiis allow one to slide on snow, in addition to making the boolit fit better.
Gilding metal is more slick than lead alloy? More slick with a grease interface?
For those of you in more southern States, how about this. You are on pavement in your car, going 60, jump on the brake pedal, you leave rubber on the road, the tires are heated, the road will be heated also. Equate road with barrel and tires with boolit. Is this a different concept? We would probably experience some of the same effect if the tires were lead and the road was smooth steel. Now, how about greasing the whole mess. Less friction, less heat and we have not burned up a significant amount of grease. 44 Man. have you recovered any boolits shot in a badly leaded bore? I think I am through with the analogies now. Can I go out and play?
The more I think about this the more thoughts I have about the projects that I have to do in the shop, such as loading some 45 70 and 40 65 ammo.


Life is good

[scrapcan]

I have say the water can be used alone to cut in a water jet. you may not cut really hard material, but look at your next single slice cheese or pre- cut lettuce, more than likely it was cut with a water jet cutting machine.

I have other examples also but that should suffice to explain that water is very abrasive in and of itself and it is way off topic of theis thread.

[leftiye]

One thing not said here yet is that the heat, however much there may be is CONCENTRATED on the surfaces of the metals due to the short time of passage (that everyone is saying prevents enough heat transfer to happen to do anything). Lead tranfers (carrys heat to cooler parts) slowly, but even steel cannot transfer heat fast enough to overcome the heat buildup in these circumstances. Witness the "Nitriding" that is the main issue in flame erosion in rifle throats. The 4000F degree flame melts the first thou or so of the metal, introducing nitrates into it. The metal becomes more brittle due to this, and flexing of the barrel under pressure causes microscopic pieces to break off. And that's not lead, it's steel.

I also think that 44 man's illustration of lead "smearing" on a sprue plate is a pivotal concept here. Not exactly soldering, but almost identical. No doubt if there was a microscopic layer of hot lead on the outside of a boolit it would do the same thing IMHO.

And last but not least - Galling. Rub two pieces of metal together SLOWLY (or not so slowly, whatever, it's not about speed like it usually is with friction.) with great pressure, and the softer metal will melt and weld to the harder metal. Not smear on, weld (or in the case of lead/steel "solder"), You'll have to treat steel that has galled like one piece and machine or file it off, (no parting line between the different pieces). And, yes, that is heat too.

I suggest we consider all of these in concert as well as other factors in this search foe the cause of leading. Super thread, very enjoyable.

[looseprojectile]

Leftiye
Now we are getting somewhere. I can imagine the interface tween the boolit and barrel needing something to reduce friction. What would be best for doing that?
Light oil? Heavy grease? Wax? Molybdenum disulfide? A combination of these?
I think that the heat from friction, not transferred to the body of the boolit, is the problem in cast boolits that lead the bore. Maybe confine the heat to the boolit?
The boolit fit and lessening the friction is the goal.
That infinitesimal surface is where it all happens.
Some would say my mind is small enough to get it in there.
Life is good

[44man]

This has been a great subject with a lot of interesting theory's. I can't say anyone is wrong or right because we just don't know what really happens. I feel this post can go on forever and we will still never know.
But I am glad to see how everyone puts in their two cents without any friction between each other.
You are all gentlemen!
Keep trying to figure this out because it is the most important part of our sport.
Looseprojectile, no, I never recovered any like that because those boolits were shot indoors at a police range and I would clean some of the guns for them. Holy smokes, talk about leading! I have never had a gun in my life get so bad. Those were all factory loads too. Just goes to show that even light, low pressure loads can be worse then 60,000# loads.
All agree that the boolit must fit the throats and be larger then the bore. However I shoot .430 boolits, medium hard cast, from my .44 with hot loads and they do not lead my bore. My throats are .4324".
What we have is called a mystery---I can't spell voodoo!

[Bret4207]

Leftiye
Now we are getting somewhere. I can imagine the interface tween the boolit and barrel needing something to reduce friction. What would be best for doing that?
Light oil? Heavy grease? Wax? Molybdenum disulfide? A combination of these?
I think that the heat from friction, not transferred to the body of the boolit, is the problem in cast boolits that lead the bore. Maybe confine the heat to the boolit?
The boolit fit and lessening the friction is the goal.
That infinitesimal surface is where it all happens.
Some would say my mind is small enough to get it in there.
Life is good

If I follow you correctly then I have to disagree. I regularly shoot as cast "oversize" boolits, as much as .005 is one particular rifle. The grooves are filled before the lands even distort the metal into them. If there was going to be "friction" it would come into play and I'd get leading like crazy. No such problem exists at the speed I'm shooting and with the loads I'm using. These PB boolits pop out the muzzle well over 1200fps with zero leading. Gotta be lube helps a bit I'd think and I still use plain jane 50/50 NRA formula.

If I misinterpreted what you said then please straighten me out.

[leftiye]

Bret, not to have my nose where it doesn't belong... I read Loose projectile as saying that lube WAS needed and beneficial. You two may in reality not disagree.

[Boomer Mikey]

The following is paraphrased from an article by Dave Scoville in the 1991 Bullet Making Annual in Wolfe Publishing’s “The Art of Bullet Casting DVD”. Available at their website and MidwayUSA.

Leading: “It may be the result of a number of factors, such as fusion, gas -cutting, friction, inadequate lubrication or skidding."

"The gas-cutting/skidding problem crops up when the bullet can’t maintain a solid purchase on the lands as it begins to accelerate through the bore. As the first driving band contacts the rifling, it tends to slide across the lands as momentum carries the bullet straight ahead. As successive driving bands take on the lands, the bullet begins to respond to the rate of twist but is still skidding. By the time the base band enters the barrel, even the slightest amount of skidding opens a gap between the lands and respective engraving on the driving bands. Hot, expanding gasses now have an opportunity to escape and burn through the gap and across the base band. In the process, alloy is deposited along the edges of the lands. As more rounds are fired, the leading is moved progressively toward the muzzle until the bore is literally lead-plated from one end to the other.”

The four most common approaches to eliminate gas-cutting:
1. Use a harder bullet
2. Cut back on the powder charge
3. Use a slower powder to reduce the rate of acceleration
4. Use a gas check – but if the bullet is skidding badly the gas check can’t control the volume of lead

“The challenge to cast bullet shooters is to hit that happy medium between too much pressure and not enough.”

Paraphrased: Too much pressure/lack of lubrication will result in leading at the muzzle and too little pressure will result in leading at the chamber/throat due to lack of obturation.

Fusion:
“Fusion is usually associated with plain-based handgun bullets and is the result of using too much fast-burning powder which generates heat and pressure very rapidly… It crops up in various degrees, from bad to worse and causes leading when the molten lead is blown down the barrel behind the bullet, literally plating the bore.”

“To eliminate fusion, there are three basic choices: Back off the powder charge, use a slower-burning propellant, or switch to a gas-checked bullet… Fusion also seems to be most apt to crop up on bullets cast from Linotype, which is not only harder than most alloys, but usually carries six or seven percent tin as well. From available evidence, the relatively low melting point (463 degrees for Linotype) and high tin content seem to be the common denominators when heavy doses of fast burning pistol powders result in fusion.”

Lubrication:
“Be careful when tempted to blame inadequate lubrication for barrel leading. Most cast bullet designs carry sufficient lubrication if the bullet is hard enough to withstand the pressures and velocity involved. The trick is to make available lubrication last until the bullet reaches the end of the barrel. In most cases, as velocities increase, that requires increasingly harder bullets – not more lubrication grooves at the expense of bearing surface… Use Alox blend as a standard and increase the load’s velocity to a point where some evidence of leading is visible, then repeat the same loads with other lubes. Assuming the bore is smooth and free of fouling from jacketed bullets, it is not unusual to find one lube provides lead-free performance and fine accuracy while others don’t. Keep in mind that other variables, such as bullet sizing, may be influencing the results” (larger diameter bullet size may improve lube retention [bm])

Gas-Checks:
“Gas checks serve as scrapers and insulators. They help reduce or eliminate leading to a considerable degree with appropriate loads in both rifles and handguns. On occasion, they may create problems where none existed before… Gas checks, being somewhat harder than lead alloys, tend to restrict base expansion and may allow combustion gasses to sneak by them and attack the surface of the base band.” (sized too small for the groove diameter [bm]) “If leading gets out of hand gas checks simply won’t be able to control the alloy build-up”

“For big bore rifle shooters who prefer cast bullets in cartridges like .375 Winchester, .38-55, 45-70 and others, wax gas checks appear to be equally effective… More importantly, whenever wax gas checks are employed, groups are remarkably consistent.”

This article; for me, was well worth the cost of the DVD set…$25.00.

I thought this might add some material to think about for the discussions in this thread. Not to be construed as the definitive answer but to add the point that there is no single cause of leading and that gas checks and larger/harder boolits aren’t always the cure. The article is too extensive to post, these are merely some highlights.

Boomer

[pjh421]

I wish I would have had the benefit of threads like this back in '94 & '95 when I was a new caster and was shooting every day.

Paul

[looseprojectile]

Bret;
This thread started with the gas check theme and I tried to wrap my thinker around that.
I have been trying to escape the use of checks as I am income challenged.
Lately I have discovered LLA and use it in wheel guns and rifles above 40 caliber with good results. No more than 1300 - 1400 fps. This is with pb boolits. I may alter the lube also.
I believe I have a reasonable understanding of what it takes to get accuracy and a clean bore at this juncture. Previously I had been expecting more power/velocity from rifles,with boolits and it don't work that way. I have realized that , if you need more power you may need to go to a high intensity cartridge with a full length gas check. Gots those also.
Life is good

[docone31]

I agree, this has been a great thread. A lot of information here.
Steel, and stainless steel barrels are actually porous. Although microscopic, there are a lot of holes on the surface layer of steel.
I am inclined to lean towards planishing.
As the bullet travels down the barrel, microscopic imperfections get a deposit. The lead is under tremendous pressure, and friction.
I have soldered ribs on barrels. It does take work, and just the right amount of heat, and flux. I am not sure, the interior of the barrels get hot enough to solder. There is heat, caused both by powder burning, and friction, however, only the bullet is under constant friction.
Nuff said by me. I have no imperical evidence to either disprove, or prove anything here. I do know, I have the privilege of reading the writings of people, who have both the experience and the desire to pass it on. Both pro and con. There is a lot of experience here, and a lot of fun just reading.
I have learned enough, from reading from this forum, that maybe this time.... I just might be able to diagnose whats up when I cast, reload, and just make a mess. I got discouraged years ago and went to jacketed only. Economic times almost make it a certainty that I will have to cast. I just got my new 185gn .312 mold from Lee. I look forward to giving this a try. I was only groping in the dark before.
I have probably picked up more information on this thread than I had learned all those years ago.

[WineMan]

Just an observation but I used a lead (WW) ingot to cushion the rifle barrel on a Russian M-38 to drift the front sight. After moving the barrel around to get it in the right spot I had numerous streaks of lead that I was unable to remove with a cloth. I had to use a brass brush to get them off. Amazing that it was so tenacious. It surprises me that barrels are not chock full of lead after a few shots.

Wineman

[MT Gianni]

Tight fit vs Loose fit: When a knife is sharp it cuts smoothly, ie with no or little friction. When a knife is dull, or has an edge with gaps and uneven wear it cut a jagged, tearing cut. Could it be that a loose [undersized] bullet is actually seeing a tearing action off of sharp edge rifling, uneven bore sizes and friction ensuing there? A tight fit would eliminate the movement of 0.0001 and the resulting expansion and wiping/tearing that results in more frictiom. Gianni