Myths of the gas check

[runfiverun]

i think swaged under pressure is a more apt description.

[NSP64]

Barrel smoothness, fouling, and forcing cone all play a part in whether a barrel will lead.

[NSP64]

After all, they can cut metal with water jets!

Seen some Navy boys try to cut a mountain with a jet.

[carpetman]

You have friction,you have primer blast,you have burning powder,you have pressure and I heard somewhere you have rpm. But you only have .00001 or some such seconds to do it in and you are going to melt lead? If you can you need to be designing cutting and welding equipment because you are much more efficient than anything that currently exists. You can train a ******* all you want but you aint going to win the Kentucky Derby with one. Take a lubed bullet and hold a torch to it long enough to get some melt? What happens to the lube. It becomes liquid,burns smokes and chars. Recover a bullet that has been shot. Lube is still there in the groove and it aint ashes---it's still lubey. Some may say lubey is not a word,but it is now,I just invented it and I must say it's a good word as you all know what I meant by it. Invent your own words and nobody can say you misspelled it. Back to the lubey lube---had it been subjected to enough heat to melt lead there would be no lube. It would spin off from the rpm's like a dog shaking water off. BTW--that was not the first word I ever invented---I have as much right to invent words as anybody else---doesn't require a license. Here's one of my all time favorites. Boobacious. She is a very boobacious lady. Everybody gets the meaning---a good word.

[Bret4207]

I invented "snogwoggin". I was drunk at the time and don't have any idea what it means and neither did the guys with but one of their wives was really, really mad at me for a long time.

[Ricochet]

Gianni, the grease on the base is protected by a thin stagnant boundary layer of gas that insulates it from the greatest heat. When gas is forced through a narrow channel at high velocity, that boundary layer is blown away.

[Red River Rick]

When gas is forced through a narrow channel at high velocity, that boundary layer is blown away.

Ricochet:

We are talking about bullets hear, aren't we?

RRR

[quasi]

Rotflmao!

[unclebill]

snogwoggin eh?
sounds risky with another mans wife!

[44man]

I pick up unburned tufts of dacron in front of the bench. With black powder I pick up handfuls of thin plastic wads that are just dirty, also thin ,.005", paper wads that are not burned after being on top of 74 gr's of compressed powder.
I suppose if you shot full auto and got the barrel glowing, you might start to melt lead but it will be from retained heat, not from the actual firing process.
There is just not enough time to melt or burn anything
Then some of you might use a SLOOOOOOOOOOOW powder!

[Ricochet]

Y'all are theorizing. I'm telling you what I've seen. Come down here and I'll show you, I can reproduce it in that Mosin with no problem. I'd appreciate it if you cleaned up the bayo, though, I've worked on it a lot from last time I did it and still don't have it all off. (I don't want to melt it off and risk ruining the temper of the bayo or its catch spring.)

I believe those of you without fixed bayonets can set up a similar situation firing beside a parallel rod with plain based boolits and a large charge of slow burning rifle powder. Just might see the same thing. Or fire through a hole in a barrier that would catch the slung droplets.

[pps]

Y'all are theorizing. I'm telling you what I've seen. Come down here and I'll show you, I can reproduce it in that Mosin with no problem. I'd appreciate it if you cleaned up the bayo, though, I've worked on it a lot from last time I did it and still don't have it all off. (I don't want to melt it off and risk ruining the temper of the bayo or its catch spring.)

I believe those of you without fixed bayonets can set up a similar situation firing beside a parallel rod with plain based boolits and a large charge of slow burning rifle powder. Just might see the same thing. Or fire through a hole in a barrier that would catch the slung droplets.

I don't care how it gets there (melting vs eroding the lead) I just know that I had some THICK deposits in my compensated tip...that I don't need for 38's anyway. The worst of it, after 100 rounds was just shy of 1/8" thick and needed an icepick and choreboy to remove.

Now that I bell the cases more, and no longer shave the boolits, no more leading, even with the Hornady swagged. With any new lead boolit I will make sure is sized right.

[Larry Gibson]

Carpetman

Very well put. The problem is many of the "experts" here don't want to here about actual tests or actual facts. They prefer abstract notions, opinions, cantations and quoting or rehashing some other "experts" same. No sense trying to talk sense to them, ask them to look at facts, tests or to even conduct their own tests; they prefer to huddle around their cauldron (keyboard) make another brew.

You, I and many, many here don't claim to be such "experts". We prefer to look at what really happens and conduct analytical tests to determine what happens. We do not set ourselves up with “a few of us can” attitude. We genuinely try to understand the loading and shooting of cast bullets. We do not set ourselves up as “all knowing’ guru’s.

Loading and shooting cast bullets is not difficult. Getting good accuracy with them is not difficult. One merely must understand there are some rules and or principles that apply. Violate those rules or principles and something can happen like leading. Some would have us believe good cast loads only happen when the stars are in proper alignment with Jupiter or some such nonsense. Some designs of cast bullets shoot better at low velocity, some shoot better at high velocity, some will lead at low velocity, some at high velocity. There are some lubes that work at low velocity and some at high velocity and some work in both. One simply must match the correct components to the rifle/handgun, there is no magic about it.

My point here is; you are right.

Larry Gibson

P.S. I really like your word!

[leftiye]

One of the rules is that a question deserves an answer. Called straight talking, and common decency.

[BAGTIC]

(1) It is not the water that allows water jets to cut metal, etc. It is the abrasives carried by the water jet. The jet is just a carriersthe way the belt carries the abrasive on a belt sander.

(2) Leading does occur. It is not caused by the lead melting. There simply is not time. Fasten a lead bullet is a vise and very quickly, as quick as possible, direct an open flame such as a propane torch across the base. Mop up the drops and send them to us.


(3) If the lead were melting it would be distributed rather evenly inside the barrel. Most all leading begins in the bottom of the grooves where it collects after being stripped off. When we use our metal files in the shop are we be believe that all the crud that collects in the grooves is there because it melted off?

(3) One of the common solutions to leading is to use a harder alloy. Why? The harder alloys often melt at lower temperatures than pure lead. If melting was the cause they should melt faster not slower and cause more not less leading.

(4) Using a slower powder is not going to 'bump up the bullet' better. It is not muzzle velocity that expands the bullet it is peak acceleration. It is necessary to have maximum initial acceleration because that produces the most G's and we want the maximum speed at the time the bullet enters the barrel. That is where the expansion takes place, not halfway down the barrel.

(5) Undersized bullets are not leading because a gas jet is cutting the sides. Gas escaping from an orifice (windage) is cooled and actually lower that its original temperature.

(6) Lead collects in the grooves because that is where the empty space is. It is not going to collect somewhere that is already filled.

(7) Undersized bullets provide such a space and because they are not an interference fit the permit more canting of the bullet so that the corners of base has more chance of being scraped off.

(8) The bullet will be heated more by the deformation of being swaged (bumped) up than by the powder gases themself. When a metal is reformed (forged) internal heat is generated throughout the object, not just at the surface, by hysteresis. That is why impact extrusion manufacturing works.

That is why if you shoot a metal plate and immediately stick you finger in the cavity it is hot. The heat was not caused by heat from powder gases yards away. It was caused by the physical reforming of the metal.

(9) A grain of sand is a particle. If the sand is melted it is a droplet. Particles of soft material, such as lead, will splatter and adhere when impacting at high velocity. Throw a mud ball against a house, did any of it stick. Was it melted?

If the lead was melted how did it stay melted during its entire passage through the bore? Chamber pressures and chamber temperatures peak after just a few inches of bullet travel. During the rest of the trip both pressures and temperatures drop very rapidly.

Good thing that expanding gas cools, otherwise our car engines might melt.

Many of us have had leaded bores. Usually we discover it when the accuraccy goes sour and we look down the bore. I have had a 6" .357 revolver barrel leaded so badly that the riflings were totally invisible the last 2.5-3 inches of the barrel.

Seldom do we check the bore after each and every shot to see which round did the dastardly deed. If we did we would probably learn that no single bullet did it. Instead it was an accretion of fouling from several shots. Now what would happen if we cleaned our barrels after every shot. One thing is that the lead would not have a chance to accumulate and each round would start with a relatively clean bore.

I believe that is the primary function of gas checks. They act like the oil scraper ring on a diesel engine piston. It scrapes off the leading deposited by the fore part of the bullet and prepares a clear bore for the next shot.

Can I prove it. NO! But at least it doesn't contradict the laws of physics.

[Larry Gibson]

pps

If you were shaving the bullets with the case mouth when seating the bullets and got leading (severe BTW) then it is obvious you were scraping (shaving) the lube off. This is evident by the fact that with a proper bell of the case mouth th bullets no longer scrape and you no longer get leading in the barrel. That is in effect a "test", i.e. effects of leading with and without a good case mouth bell. you narrowed the parameters down, located the problem and eliminated the problem. I know you did not intend on conducting a test but merely wanted to end the leading. The result was the same. Your results are "facts". As Ricochet points out "to many are theoirizing" instead of looking at simple facts.

Good job getting the problem solved.

Larry Gibson

[Larry Gibson]

One of the rules is that a question deserves an answer. Called straight talking, and common decency.

Ask a straight question then. I'll give you a straight answer. Don't bellyache and whine if you just don't like the answer as you most often do. You ask the question, I'll answer. That simple enough for you?

Kindly; If it applies on this thread then do so here. If it applies on one of the others please post there. If you want a new thread, start one.

Larry Gibson

[sundog]

Seventh Grade National Championship Spelling Bee ---

Little Johnny approaches the microphone.

Little Johnny, your word is 'boobacious'.

Little Johnny's face get seriously screwed up!

Boobacious. What part of speech is it please?

It is an adjective.

Boobacious. Can you use it in a sentence please?

Boobacious. Carpetman has a boobacious avatar.

What is the origin please?

Carpetmanian.

Suddenly, Little Johnny's face has a sly smirk...

Thank you. Boobacious. B-O-O-B-A-C-I-O-U-S. Boobacious!

[Bob Krack]

1) It is not the water that allows water jets to cut metal, etc. It is the abrasives carried by the water jet. The jet is just a carriersthe way the belt carries the abrasive on a belt sander.

(5) Undersized bullets are not leading because a gas jet is cutting the sides. Gas escaping from an orifice (windage) is cooled and actually lower that its original temperature.

Ever see a "Plasma Torch"?

(6) Lead collects in the grooves because that is where the empty space is. It is not going to collect somewhere that is already filled.

(7) Undersized bullets provide such a space and because they are not an interference fit the permit more canting of the bullet so that the corners of base has more chance of being scraped off.

The leading edges of the engravings are scraped and the trailing edge is 'thrown" off - and the softer the projectile (and/or the less capable lube), the more is scraped off..


I believe that is the primary function of gas checks. They act like the oil scraper ring on a diesel engine piston. It scrapes off the leading deposited by the fore part of the bullet and prepares a clear bore for the next shot.

You are probably 99.9% correct there!

A gas check also supplies a uniform shaped base - that is - no sprue cut, no tall side because of the sprue cut, no deformation from a slightly molten base at the sprue.


Can I prove it. NO! But at least it doesn't contradict the laws of physics.

Me Too!
Vic

[Lloyd Smale]

Im far from a scientist and wont do much therorizing here but my thought goes to the non melting side. Smokeless powder burns it doesnt explode so a good part of the bullets path down the barrel is cushiioned by unburned powder. Now this may not be the case with bullseye or other fast burning powders but when were talking leading its usually high performance ammo with cast bullets shot fast and in those cases your usually using a relitively slow burning powder. Personaly i think its more the friction tearing off lead and ill fit bulets cause it and the faster you shoot them the more it shows up. I can take one shot out of an ill fit gun every day for a month and see leading and the barrel isnt even showing signs of being warm after one shot. Once you get a trace of lead in your barrrel its just going to keep attracting more lead as the next bullet passes over it. Im even having second thoughts as to how much lube plays a part in actually lubricating a barrel to prevent this friction after recovering about a 100 bullets out of the snow this year lubed with a lube at least as soft as javalina and seeing how little lube is actually used. I was allways followed the group of people who believed the bullet being shot was lubed by the lube left in the barrel by the previous bullet. But seeing how little lube is used and the ammount of smoke you get with a aloxed based lube id about bet a dime to a dollar that any lube put down by a bullet going down a barrel is burned away while that bullet is being shot. Maybe enough lube and burned residue of lube is left behind to create a barrier that helps prevent the lead from sticking somewhat to a barrel but what makes me doubt even that is what flux does in soldering is block oxegen from metal to allow two metals to stick and bullet lube and soldering flux are very simular as some fluxes are wax based so why wouldnt it actually allow for the lead and steal to stick together even more especially if you were in the camp that believes that lead melts in a barrrel. then theres this thought. If your soldering metal the lead wont stick until the metal your soldering it to is about red hot. So how does it stick to barrel metal when shot in a cold barrel. i surely dont know the answer to this leading thing and what lube really does in a barrel. I dont think anyone really does and mostly all of this is just a matter of opionion mostly gotten from other people back when there was no real way of testing to prove any of it. All i know is lube is a neccisary evil in shooting cast bullets. Whatever its doing in my barrels is needed and i guess it really doesnt matter to me and its not worth lossing sleap over or getting wound up trying to argue my point. it is because it does and does because it is and thats good enough for me.