Myths of the gas check

[bhp9]

One of the great myths about using gas checks is that they prevent leading. Well although it is true that a very small amount of leading can come from the base of the bullet, about 98 per cent or more of leading comes from undersize bullets which let the gas escape around the sides of the bullet, melting the sides of the bullet which in turn can cause some really severe leading.

Years ago I had a .44 magnum pistol that leaded like heck and gas checks did absolutely nothing to stop the leading. Even using pure linotype did not stop the leading either. The problem was one of an under size bullet and because the mold would not throw a larger size bullet I had two choices. Use a slower burning power and more of it to obdurate the bullet so that it filled the bore or go to a softer bullet (much, much softer) and keep on using a small amount of fast burning power that I was using for low velocity mid range loads. The soft bullet was able to obdurate with small amount of power and still seal off the chambers and bore.

So if gas checks do not stop leading then why do I use them, because in rifles, not pistols, I have always got much more consistently smaller groups when using gas checks. The gas check prevents the bullets base from being distorted by the hot burning gases. Once the base of the bullet is distorted you can forget consistent accuracy. This base distortion is due to the much higher velocity that I push my cast bullets in rifles to as compared to pistols ( between 1,700 and 1.900 fps. in my rifles) I always seat the bullet within the case neck to prevent the gas check from coming off as the bullet exists the cartridge case and it also prevents any gas cutting of the sides of the bullet. When the bullet is seated down into the powder charge the gas check will only protect the base of the bullet from being distorted by hot gases, not the sides of the bullet.

I generally like to keep my cast rifle bullets up to around 1800 to 1900 fps because when they are loaded down to move slower the wind just plays to much havoc with the accuracy.

I do not use gas checks in pistols as most of the pistols I load for are not the magnum hunting type pistols but standard velocity military pistol calibers.

[Ricochet]

Another option when the boolit is slightly undersized is to seat the gas check in a properly sized sizing die. At least the check on the base will seal better.

[pps]

I can't say much about the gas checks, but I can attest to the fact that under sized bullets will severely lead the barrel. Here is a pic after 100 rounds of 158gr Hornady swagged lead.

158gr over 3.4gr bullseye in 38 cases...chrono at 850fps

This occurred because on my first venture into handloading, I failed to sufficiently expand the cases before seating. One of the bullets I pulled measured .356...compared to .358 on the ones in the box. Since belling the cases a bit more, and a dose of LLA there's no more leading.

[PatMarlin]

THat is a COOL photo!...

[carpetman]

I have serious doubts that any part of a bullet melts in the barrel---just aint there long enough.

[pps]

I have serious doubts that any part of a bullet melts in the barrel---just aint there long enough.

If you had to clean the lead splatter out of my muzzle brake with an ice pick and a chore boy you'd have no doubt the flame and pressure blows molten lead all over the place...even the top strap.

[Lloyd Smale]

Nothing will prevent leading if you have a missmatched bullet. If your bullets are sized properly for your gun gaschecks will allow you to shoot at higher velocitys without leading and will usually give you better acuracy. Probably due to the fact that you have a more consistant base for the gases to push on.

[Bret4207]

If you had to clean the lead splatter out of my muzzle brake with an ice pick and a chore boy you'd have no doubt the flame and pressure blows molten lead all over the place...even the top strap.

It's not melting, it's eroding it and the alloy pushed off adheres the the metal. It's seems like "melting" is the term many use to describe this, but it isn't accurate. If you go back through the older posts here you'll find dozens discussing this at length in depth. There just isn't time for the metal to melt.

[44man]

Thats correct, the lead does not melt but is stripped from gas jets working on it. After all, they can cut metal with water jets!
Another thought about gas checks is how they work when fired. If you take a good look at the base of a PB, fired boolit you will see lead has been extruded to the rear to form fins around the edges. Not a problem with a good fitting boolit or one that is started straight but if a boolit starts a little off, the extrusion will be greater on one side then the other. When it leaves the muzzle it will be blown sideways by escaping gas.
The gas check helps hold down the extrusion to some extent.
I shoot all heavy loads in my revolvers with both PB and GC boolits and I can't detect whether one is better then the other. Leading, what tiny amount there is, never changes. A few tiny strands on the first patch no matter how many months between cleanings. Accuracy is the same with either boolit.
It makes me wonder if paying for the checks is worth it. Maybe in the real high pressure stuff like the .460 or .357 max.

[Papa smurf]

bhp9 ---- Very good read. Your right on the money!

[pps]

It's not melting, it's eroding it and the alloy pushed off adheres the the metal. It's seems like "melting" is the term many use to describe this, but it isn't accurate. If you go back through the older posts here you'll find dozens discussing this at length in depth. There just isn't time for the metal to melt.

That's fine, I'll concede to calling it eroding. The end result is the same in the sense that a bullet to small for the bore will allow more of the gas to rip lead off the bullet and deposit it all over the barrel.

[Dale53]

44man;
I NEVER use gas checks on .44 magnum or .357 magnum full loads and I have NEVER had a leading problem. I DO use properly fitting bullets. Well, I lied just a bit - I have on occasion used the Lee .430-310-RF and it is a gas check bullet (wonderful accuracy with that bullet, by the way) and it is the heaviest hitter that I have used in the .44 magnum.

However, my biggest game with handguns has been large whitetail deer. The .44 Keith does a fine job on these. Dead is dead. If I hunted bigger game with a handgun I definitely would use the Lee. Frank Siefer and I designed this bullet and it turned out to be a wonderful performer.

My "go to" bullets are plain base for ALL of my revolvers. I recently acquired a .454 Casull Taurus Raging Bull (what a name) and WILL be using Lee's gas check 300 gr RF bullet in this as the velocities will exceed 1600 fps. Up to 1400-1500 fps, there is really no need for gas checks, in my experience, and with the recent cost increases, that only makes me HAPPY! Even with the .454, no doubt, my practice bullets will be plain base bullets driven no faster than 1400 fps.

Dale53

[Ricochet]

Lead that's eroded off the sides most certainly IS melted. Or can be. I still have a few drops of it soldered onto the bayonet of a Mosin M91/30, after spending a lot of time and vigorous effort chipping and scraping the bulk of it away. Water dropped wheelweight .315" plain base Fat 30 TL plinkers lubed with LLA, run at ~2000 FPS over IMR 7383 is what did it. Funny thing is, it didn't lead the bore, but it COVERED the proximal bayonet with splattered lead!

[jonk]

I would dispute that a bullet cannot melt. I agree generally it doesn't but allow me to relate...

A few years ago I was shooting a 6.5 Carcano with surplus ammo. A lot of hangfires. One round apparently wasn't charged with powder at all (sabotage? Or just crappy Italian quality control?) The primer alone had enough oomph to drive the cupro-nickel clad lead base bullet into the rifling and lodge it there. Fortunately I noticed this.

I was about 20 rounds into things when this happened, fired over perhaps 5 minutes. The gun was pretty hot but not smoking or anything.

So I go and get a rod out of the trunk and a small hammer and tapped the bullet out. I'd guess it was lodged in the rifling for 2, maybe 3 minutes.

Upon driving it out I found that a bead of lead had melted out the bottom of the bullet and re-hardened when it reached the chamber. So the temperature in that barrel had to be 500 degrees or so. After just 20 rounds of high power rifle ammo. Over 5 minutes. Through a fairly thick cupro nickel jacket.

This suggests to me that if you fire off a string rapidly and chamber a round it most definately COULD get hot enough to melt, perhaps in the chamber, certainly if engraving the rifling. Not that that happens to most folks, I'm just saying it can.

[docone31]

Here is where I wonder. I have noticed, when soldering steel, or iron, I have difficulty unless the proper flux is used. I wonder if the leading is more planishing. That would explain why with a tight fitting bullet, there is little as compared to one that is more loose in the bore.
I see it in the jewelery I make. With polishing I planish rather than grind away. Gold, and silver, shows the same drag marks as in the photo when it is first started.
There is tremendous pressure behind the bullet, as well as the extrusion on the bullet traveling the bore. Even on my high polished tools, I see the same traces although more microscopic. This could be that lead is softer than the materials I work in.
No matter what, it is certainly an issue. I have just loaded 20 test bullets for my .303 British. I am hoping it will not be time for major elbow grease! I only did 20, and I plan on firing a few commercial loads to scrape away anything really major.

[Ricochet]

I have noticed, when soldering steel, or iron, I have difficulty unless the proper flux is used.

I've noticed that, too. Apparently a mixture of gun oil, burned LLA and IMR 7383 residue makes a pretty good flux on blued steel.

[leftiye]

Plus one as to boolits can and do melt in the barrel. Both from heat of friction, and flame temp, also due to flame temp while blowby is occuring. There was a post recently where the info was about someone actually using some apparatus to read the temp of a bullet just leaving the bore. It tested out at 500F plus FWIW. Bullet temp. I think it was JoeB on his thread "Do cast boolits blow up? who posted it. Flame temp of 50,000 psi loads has been known for over 40 years to be 4000F.

[454PB]

Dale 53, you're gonna establish a new relationship with gas checks if you push that RB to it's full potential!

I've had one since they first came out. Yes, you can certainly use your light loads without GC, but the ones pushing 60K really like them.

[Bret4207]

IMO you are confusing melting with eroded lead particles adhering to the metal. Yes, it looks like drops of solder, but it isn't. I think the lead is eroded off and the atomized particles are forced against the metal under great pressure. The soft alloy will adhere to the imperfections in the barrel. In truth it may as well actually melt, there's no practical difference from what I can see. There's also the issue of the lead alloy galling into the barrel. Anyone who's ever slid a file across anything sees what is happening. The imperfections in the relatively hard barrel allow the lead alloy to gall and remain in the barrel. Again, it may as well be melted. Same with Ricochets lead spray on the bayonet- atomized lead eroded off the boolit at great pressure adheres to the steel like a soft snowball thrown against a barn wall.

As for the temps and pressure involved, there's no doubt it's as hot as posted. The problem becomes one of time. The time it takes for heat to transfer to the alloy and heat it to the melting point is considerably longer than the time the boolit remains within the confines of the barrel, or so it is reported. I don't know what the actual time is and I imagine it varies with load, bore size, boolit alloy, etc. We're talking micro seconds and any thing between the boolit and flame like lube, COW, dacron, etc. will add to the needed time. It's pressure and poor fit that causes leading boys.

All this means nothing in the real world. Leading is leading and we know how to prevent it, what causes it and how to remove it. All we're doing here is defining a point.

[MT Gianni]

For those in the "it melts Camp", try putting some grease on the bottom of a gas check, loading and firing it where the check can be recovered and then please explain to me why it doesn't melt grease. Gianni