Gas cutting/ Melting bases

[fecmech]

In a previous post on Goofy Lubes there was some discussion as to whether or not propellant gases could melt the lead on the base or sides of a bullet in the short time they had to work on them. A friend took some pctures of bullets I had recovered in the past fired into snow. The first pic shows 2 lee 214swc sized .429 lubed with 50/50 alox over 7 grs of green dot fired out of a Super Blackhawk with .434 throats. Gas cutting is severe and the melted lead is obvious, leading in the barrel was bad. Next pics are .45 slugs sized to .433 with same load, lube, and gun and very slight cutting on the edges of the base.
Next are 3 bases from a .357 mag, left one is Blue Dot, middle is AA#9, don't know what right one was. Loads were in the 1300fps range. The melting is obvious as the sprues are gone and surface shows smoothing. These bullets had no blow by as they were sized right and you can see that in the last picture. As you can see bases do melt and if the gases get past the bases in any great amount accuracy goes out the window.

[beagle]

I've seem similar bases. I still don't think they're melted but show the impact of the powder upon impact caused by the first nanoseconds after the primer fired and before ignition. I've fired 4227 and you can almost see the granule impacts in the base.

The rounded edges clearly show rounding which is caused by errosion before the bullets bumped up and sealed. That's normal for almost any cast bullet as well.

In fact, if you recover gas checks, you'll see that they're burned in the same area or marked with black residue.

I recovered some fired into steel plates from a Marlin 30/30. They had expanded to their full diameter when the bullet impacted and rebounded about 15 feet. They showed the black residue wher the bullet edge was.

The real problem is the errosion on the sides. Now, that's blowby and what causes the problems. Both leading and inaacuracy caused by leading.

This is an area that I feel that can be improved on by the CF Ventures soft gas checks and I've been meaning to try them but its one in a long line of projects.

A powdered filler would probably improve accuracy in this case./beagle

[buck1]

Soft checks??? Sounds interesting. I have never seen them. But I am going to check it out , thanks...Buck

[Willbird]

I belive they are punched from plastic milk jugs...


Bill

[anachronism]

CF Ventures soft checks are made from what appears to be a form of dental wax. They work well, but remember to reduce your loads accordingly...

Bob

[Crowkiller]

The CF Ventures checks look just like pink baseplate wax. Ask your dentist for a sheet to try it out. I think the wax is a blend of beeswax and parrafin. Just do not leave your loads in a hot car in July.....

[Char-Gar]

Count me in the number that doesn't think those bases show melting. IMHO they have been blasted/abraded by the as yet unburned powder. I have seen many such bases and if the alloy is soft enough you can clearly see the indent made by individual grains of powder.

[fecmech]

"The rounded edges clearly show rounding which is caused by errosion before the bullets bumped up and sealed. That's normal for almost any cast bullet as well."

Beagle--I disagree with your statement above. I thought the pictures showed the melting pretty clearly but when you look at the bases through a loupe the melting is even more obvious. The sprues imo were not "eroded" they have been melted away. If you look at the very bottom edge of the 3 bullet group you will see where the gas momentarily got past the edge of the base and it looks like the edge of steel cut by a torch. Also where the gases got into the lube groove in the first picture the melting is pretty plain. As long as the lube and base of the bullet keep the gas from comming past the sides of the bullet I think you are ok. The Blue Dot and AA9 loads that show on the bases are accurate magnum handgun loads that run on average less than 3"@50yds and the Green Dot Load is too when sized properly. The pictures were posted in answer to John H in his reference to Glen Fryksell and his statement saying gases went forward melting the lube and blowing it down the barrel ahead of the bullet( which I disageed with). John did not believe the gases could melt the lead due to the short time frame involved nor did a couple other posters. After picking up many bullets and examining them over the years it is my firm belief that melting can and does occur. Nick

[454PB]

A few years ago I bought a Taurus Raging Bull. It's the first (and only) gun I've had that has a ported muzzle. After cleaning and examining the ports, I'm now convinced that what I always believed was "melting" of the bullet base is actually caused by hot, high pressure gas blowing past the base of the bullet as it exits the muzzle. We've all seen the giant plume of a fireball from the muzzle of magnum pistols. It not hard to imagine the effect that fireball has on the base edges of a cast bullet as it exits the barrel. Like Beagle, I've seen the same effect on gas checks.

On the Taurus, this debris of bullet lube and lead builds up quickly, actually coating the sides of the front sight blade and the non rifled inch or so of barrel within the porting area.

I don't even care if the bases of the bullets look bad after firing, as long as the load is accurate, and the barrel isn't leading.

[Bass Ackward]

[QUOTE=fecmechI thought the pictures showed the melting pretty clearly but when you look at the bases through a loupe the melting is even more obvious. The sprues imo were not "eroded" they have been melted away.

The Blue Dot and AA9 loads that show on the bases are accurate magnum handgun loads that run on average less than 3"@50yds and the Green Dot Load is too when sized properly.

John did not believe the gases could melt the lead due to the short time frame involved nor did a couple other posters. After picking up many bullets and examining them over the years it is my firm belief that melting can and does occur. Nick[/QUOTE]


Nick,

You are absolutely 100 % correct. And you are dead wrong. How can this be?

It all depends on how you shoot cast. If you shoot the Elmer Keith fashion with undersized bullets, then you can and do get gas cutting until obturation. Hard bullets magnify the problem because it focuses the escaping gas into a smaller space amplifying the heat for a longer period. Slow powders take longer to build pressure and cause obturation, so they cause more erosion even at the lower pressures they generate. That's why this method produces the best accuracy when either useing super fast powders or slow powders at magnum charge levels. So you are 100 % correct. Remember, Elmer shot a 16 to 1 mix. (10 BHN) That was super hard to him and his customers as he sold bullets and ammunition commercially for people going to Africa. Imagine the thought of that today. Many of his customers threatened to desert him if he .... EVER .... put antimony into his mix to harden the bullets.

Now, if you shoot cast bullets like rifles and go .001 over throat diameter, obturation (seal is all that means. Anything more is deformation.) occurs much quicker than with the Keith method. If no gas can get by the bullet, then their is an air barrier at the base of the bullet that buffers the expanding gas wave where virtually no heat can hit the base. How do I know? Because I would drill a cavity in the bottom of the bullet and fill it with lube. Not only does the base not melt, but the lube is still in there as well. One fellow, Norm Johnson, shoots 357 Magum velocities without ANY lube using this method and never leads. No gas cutting either.

So the answer as usual depends on how you are shooting.

The advantages of the Keith method proliferate because they are supported by the gun manufacturers and the mold and powder companies. Why? Because it cuts the most pressure and uses the most powder! If you believe that the less gas cutting, the better the accuracy, then you have love the rifle method. No more fooling with crimp and neck tension because your ignition comes from a much more consistent sourse than they can ever be .... your bullet. But the keith method of sizing allows higher velocity figures to sell guns with weaker frames.

You can still shoot the "rifle method" (as I call it) in weaker guns. It just requires less powder to match the same pressure level so that you get the same velocity and accuracy level you did before. Instead of 7 grains of Green Dot, you may only need 6.5. Less if you feel compelled to shoot hard bullets. But this method shines if you want to burn the slower powders at lower velocities. Especially Blue Dot to 2400 range. Slower than this and you still need full charges for safety. IMO.

With the bullet sized .001 over throat diameter, 16.5 grains of 2400 works with everything from 200 to 250 grains. It produces @ 1100 - 1200 fps with about 25,000 psi. It burns clean and you can use dog stool for lube if you want. But I never shoot anything cast over 14 BHN in a wheeler anymore. And 8 - 10 Bhn works even better.

[JohnH]

fecmech, Thanks for posting the pics. I don't doubt that gas cutting ocurs, I've run cutting torches far too long in my life to doubt that. What I do doubt is that there is enough time in the barrel for the required transfer of calories to take place to make anything melt. In the case of gas cutting we are not talking about caloric content, btus or anything else, we are talking about a high pressure stream of gas and even particulate matter gouging a hole. It is not even like what occurs when using an oxygen/acetylene torch on steel. In that example, the torch flame heats the steel to near melt, the oxygen accellerates the melt and burns the steel, the extra pressure does nothing but blow the burned steel out of the kerf.

In gas cutting on a bullet, there is no heat transfer The high pressure simply gouges out a path in the bullet. Lead particulate may be vaporized, but melt is hardly the proper description of the phenomena.

Don't mean to be picky, but it is like saying an explosion occurs when gunpowder is ignited, Gun powder does not explode, it burns, very rapidly. Gun powder is not an explosive, it is a flammable solid.

I readily admitt I am ignorant, and hardly in a position to argue the fine points of Mr Fryxells article. I'll say again, reading it did give me a deeper understanding of what lube does for us. While we may argue what lube does and how it does it, I don't think anyone would argue that it does nothing, otherwise we would be recommending that people not use any at all, Why do something that is unnessicary?

Perhaps starting at the point that lube does something will be an easier path to finding out what it does and how.

I will also agree that it is somewhat ridiculous to concieve that a material I can squish between my fingers is going to seal off a high pressure jet stream. That don't make sense either.

But there is definately exellent lube, really good lube, good lube, ok and lousy lube. At one point in time or another I have encountered and used examples of each of these.

Why does one fail and one not? Why does Emmerts work good till velocities
reach about 1400? Why does FWFL seem to work good at most any practical velocity? Why does my goofy lube produce statistically better groups in three rifles that FWFL does? Is Goofy Lube Better? Why does 50/50 FWFL and Goofy Lube perform even better? Why does Lyman Super Moly work good, but right at 200 rounds the groups go to hell in a hand basket, but i can shoot goofy lube till the gun is so dirty it won't lock up proper before I see a degradation of groups?

I still think that when the bullet is a proper fit to the bore that gas cutting is a rare phenomena. If it weren't, cast bullets wouldn't work nearly as well as they do, and not nearly as many people would be able to have good success with them.

Successful cast bullet shooting is a combination of several factors including at least, good bullet, good bullet fit, good alloy for the pressure/velocity, good lube for the pressure/velocity, good barrels, well balanced loads. Lube is only one peice of this puzzle.

Again, Thanks for the pictures. Shooting into blocks of wood I don't get to see fired bullets like that often.

[StarMetal]

I'll side with Beagle on this one. Believe it or not the gas pressure concentrates in the center of the bullet base. That's why the sprue is gone in that one bullet pic and appears as though it were melted. Compound this pressure with the blast of gas, unburnt as of yet powder, and carbon, it is really eroded away as
Beagle said. I've recovered countless number of gaschecked bullets where the gas pressure push the center of the gascheck in, very much concaving it. Thing about it, the sides of the bullet are supported by the stell walls of the barrel, plust the sides have friction against the barrel, so the center is the easier mass to move, thus it gets pushed in or cupped. I believe the wash one sees like in muzzle breaks, etc. is the gas blowby that blows by the sides of a bullet for whatever reason..poor fit, an irregularity in the bullet, etc, but this is gas erosion. The gas is under very high pressure. I'm sure you all are aware that you can cut steel with high pressure water. Well this is what is trying to go inside the barrel behind the bullet, but with high pressure hot gas. I've recovered paperwads, plastic wads, dacron, kapok...all with a much lower melting or burning point then lead...why don't they get burned up? Just my two cents.

Joe

[Maven]

I haven't recovered enough PB cast bullets to determine whether they were gas cut or not, but I've certainly seen concave gas checks on recovered, heavy CB's, namely the ~235gr. Buckshot 8mm bullet over 48gr. IMR 5010 with .3cc filler added.

[StarMetal]

I've always been fascinated by finding shot bullets and seeing the rifling on them ever since I was a kid. I mean it's like you see it in the gun, then boom, you never see it again. So to find one was exciting. Thus my quest for recovering bullets still lives on. I've recovered, let's say, alot of bullets, from cap n ball, muzzleloaders, handguns, rifles, to rifled slugs from shotguns. Never once have I seen actual melting.

I have a test coming and after I perform I'll post it here.

Joe

[JohnH]

I've recovered paperwads, plastic wads, dacron, kapok...all with a much lower melting or burning point then lead...why don't they get burned up? Just my two cents.

Joe

Exactly.

[fecmech]

Hey guys why don't we agree to disagree and leave it at that. Nick

[Buckshot]

Hey guys why don't we agree to disagree and leave it at that. Nick

.........Nick, just sounds like a good healthy discussion to me. No ones getting whacked over the head here:grin:.

Personally my feeling is that due to the very short length of time that the boolit's base is exposed to the heat of combustion, no wholesale melting can take place. I will readily agree that a very tiny thin layer of lead may actually melt due to the intense heat, regardless how short a time it's applied. This may account for a partial blurring of sharp features on the base.

I think too that probably pressure, primer and powder grains/debris are most likely the prime movers in any base deformation due to impact with the base.

I do not recall offhand seeing any recovered cast boolits of mine fired over smokless powder which showed gas cutting. However, I have seen 58 caliber Minie' bullets I've fired that had been gas cut, and the effects are singular when this happens.

First of all for serious gas cutting to occur, the gas has to be able to go to a low pressure area freely. And this low pressure area has to contain enough freespace to allow a quantity of gas to flow. It cannot merely be a lube groove only half full of lube. Or in fact, 2, 3, or 4 lube grooves only partially filled. For real gas cutting to occur the gas must be free to pass into the atmosphere ahead of the slug as it travels down the barrel.

One possible explaination for the severity of the gas cutting I saw on the Minie' boolits was due to the high particulate level of the high pressure gasses escaping past the slug. I forget now the percentage of the charge that is ejected after the bullet clears the muzzle, but it is a sizeable percentage of the charge wieght.

In any event the portions of the slug which were cut were unmistakeable in what had happened. I have wished before that I had retained a few of these Minie' bullets. Gas had cut through each drive band leaving a sharply defined edge with an almost shiney trough. Kind of like termites leave in a piece of wood. Maybe a better illustration would be like what a small watercourse might leave through a mud flat.

None of the gas cutting was in a straight line, as the gas had found it's way through creases and voids that had bisected the drivebands. Gasses blew into the bottom lube groove, made a right hand turn and traveled a short distance and then blew past the middle drive band into the next lube groove, and so on through the next until freed past the turn of the ogive into the atmosphere.

Speaking of Minie' bullets, I have also found them where a void had formed in the slug, just above the HB corepin. While visibly perfect, upon firing the fragile layer of lead disintegrated under the pressure to expose the void.

................Buckshot

[David R]

This gas cutting, to me makes total sense. Think of the hot gasses and powder mixed are like a sandblaster. Once they start to get by the boolit, away they go out of control.

I use a Plasma cutter at work, nothing fancy, just an arc behind some focused shop air. It cuts with out preheating like a torch.

So we have HOT gasses, mixed with High pressure and the abrasive powder. Sure could destroy accuracy if it gets past the boolit.

Great Discussion and great reading for me, Thanks guys

[fecmech]

[QUOTE=Buckshot].........Nick, just sounds like a good healthy discussion to me. No ones getting whacked over the head here:grin:.

Buckshot--I aggree and I did not feel like I was getting whacked and some good points have been raised. I look at the bullets and to me the surface layer shows melting. If others see something different then that is what they believe and I respect that. I was pretty impressed with my buddies camera work, he did a great job on the pictures. I think I may be buying a camera like that in the future. Nick

PS. DaveR where in western NY are you, I'm up in the Gasport area

[beagle]

I'll agree 100% on gas cutting. It does happen when the pressure exceeds the bullets ability to effectively seal the bore due toa very soft, weak alloy or an undersized hard bullet or higher pressure than is designed for a cast bullet.

I was shooting some 225438 bullets ina .223 a couple of weeks ago using WW alloy and got a little carried away by velocity. These were clocking 2486 FPS average and I was getting blowby as evidenced by whitish looking smoke out the muzzle. Accuracy was "minute of 8 X 11 paper" at 100 yards.

I've also done this with some moly coated 30/06 30-180-SPs that I attempted to push to 2600 FPS. I mined a lot of lead out of the barrel after that one.

I'm of the opinion that one of the prime reasons that cast bullets get a bad name is the use of hard, undersized bullets in revolvers. That's nearly a surefire method of getting leading...and blowby. My peeestol bullets are usually WW cut with a bar of pure per pot. I make them big and the diameter combined with the bump usually seals things and I don't get that much leading. Of course, shooting wimpy loads don't hurt either as I'm no speed demon when it comes to shooting./beagle

[David R]

Big snip....

PS. DaveR where in western NY are you, I'm up in the Gasport area

This is cool, If I yell out the window, you might hear me. I live in West By Golly Shelby. I have a garage in Lockport and belong to Hartland Conversation Club.


Send me a PM please.

David