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Thread: Heavy high caliber lead bullets ...gas check or no gas check?

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    Default Heavy high caliber lead bullets ...gas check or no gas check?

    Time for another educational question...

    I've heard some say that large heavy higher caliber cast lead bullets don't need a gas check. Others say they do, and most places that sell bullets like these always put gas checks on them. What's the reasoning behind a gas check and how do you decide if you want it or not? Does it have anything to do with lead hardness versus velocity, i.e. soft lead at higher velocities needs a gas check? Or what? Does a gas check distort so the skirt fills the rifling? Teach me...

    Brian

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    Default Heavy lead bullets with or without gas checks

    Heavy lead bullets generally means large calibers and slower velocity. For something like a 500 gr. 458 bullet in an older .45-70 with reduced loads a gas check is probably a waste. Shooting the same bullet loaded heavy in a .460 WbyMag you will probably need a gas check. In between will depend on your powder, velocity, leading or lack it, bullet alloy used, bullet lube, and the accuracy you get and desire. Some of the best groups I've shot with cast bullets were with made for but not used with gas checks but the velocity was low.

    Unless you are shooting heavy loads I'll try it without the gas checks first. The gas checks used to be cheap - $4 or $5 a thousand; the .50 S&W GCs are over $50 /thousand. Why add 3 or 4 cents to the cost of a round if you don't need to.

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    The name of the appliance tells you what it is, and does. For black powder they aren't necessary. Any non-jacketed projectile I have will have a gas-check on them. It keeps the hot gases from cutting and eroding the base of the bullet. The pressures in a modern firearm can reach 65,000 psi. Lead will run like water at that pressure, and with the 3000* temps of the propellant, lead will simply vaporize. When that happens, you get leading in the barrel, this usually occurs in the first four inches of the barrel. It is a pain in the a-double-s to get out, so why not order your bullets with a gas-check?
    Great spirits have always found violent opposition from mediocre minds. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence. Albert Einstein

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    Default Obturation......

    When dealing with hard cast bullets we generally refer to the hardness being about BHN 18 and higher. Or to be more specific bullets that we do not want to expand. Also these bullets need to be ductile as well, meaning they will not break, shatter or chip away at the nose on impact. To do this we heat treat bullets from an alloy of lead, tin, antimony and arsenic. This bullet is now so hard that it will not expand on impact or when hit in the butt with a rapid burst of pressure. This bullet now will not "bump up" or obturate to fit the grooves until the pressure is very high.

    Well, if it does not obturate and fill all the space around the base of the bullet, this hot and high pressure gas will erode away some of the base of the bullet and weld it to the bore of the gun. A gas check will seal the gas off from getting past the bullet, like a gasket. For a bullet of 20 BHN it takes over 38,000 psi to start to obturate the bullet and seal the bore. The gas check seals at much lower pressure and allows the use of this extra hard bullet at less than max pressure. It also serves as a shield from hot burning powder from softer bullets and this is beneficial for varied bullet hardness ratings. Also when using cast bullets, regardless of how hard, certain powders work better than others. 2400 and Unique have been used for over a century with cast bullets of varying hardess ratings and kept leading down. They are not always the best powders when the top velocity is needed for magnum big bore revolvers. With a gas checked bullet we need not be so critical in our selection of powders for the cast bullet. H110 and Lil'Gun and to a lesser degree H4227 are pretty hot powders when at max or near max loading. A gas checked bullet is best with these powders and most other powders for even moderate loads.

    A gas check makes a better and quicker gas seal at the forcing cone of a revolver and reduces cutting and gas erosion at this critical point, prolonging accuracy and revolver life.

    A gas check allows a variety of powders and load charges and a varying BHN number to be used without concern for leading. The gas check also allows the use of any powder in magnum revolvers to acheive the highest possible performance. I really think the magnum big bore and bottle necked rifle cartridges need gas checks. It isn't just velocity that causes leading. Leading of a bore can occur at very low velocities.

    Using flat based bullets without gas checks can be done and at less than 18 BHN with certain powders and load densities with very good results. If a bullet is designed for a GC one should be used s this "tapered heel" tends to funnel hot gas down the side.

    You're a good and curious student, Brian
    Last edited by Murphy; 03-05-2008 at 23:35.
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    Sounds to me like using gas checks all the time is not a bad idea. I need to start shooting after work so I can use up more ammo and try more stuff...

    Thanks,

    Brian

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    Default Gas checks for cast bullet loads

    In an idea world we would all use jacketed bullets and not have to worry about gas checks at all.

    For many of use we use cast bullets to save money and allow us to shoot more on our limited funds. If I can safe 4 or 5 cents per round by not using a gas check it can add up.

    As stated in my inital post bullets made for gas checks generally work find without them at lower velocities and lighter loadings. At moderate preesures you may or may not need them; I always use them on heavy magnum loads.

    The old standard Lyman gas checks are smaller than the diam. of the bullet anyway - that is why they don't even hit the sides of the sizing die. Hornady crimp on gas checks are larger and thicker and come out of the sizing die about the same diam. as the bullet. I can't find a .30 cal Lyman CG handy but a 35 cal one measures around .355 diam - that is hardly a good seal for a .357 magnum bore. I generally use the Hornady gas checks but I've shot quite a few bullets with Lyman GCs over the years - guess they have been around for 75- 100 years now.

    As to melting the base of the bullets and gas cutting - I've never seen a recoverd bullet the looked damaged from such and I've look at a LOT of recovered bullets. If ou show use a picture of one so damaged I'd love to see it - I learn something new every day. I've likewise examined a lot of full metal jacket bullets with an exposed lead core on the base- I've never seen one that showed any sign of melting. My observations match those of many others over many years.

    One except I do recall where you do need to use gas checks always is in a gas operated rifle like the M1 carbine. We used to plug the gas piston up on full auto fire with plain base cast bullets loaded to military velocities - I had a legal M2 down south - and occassionaly I had to pull the piston and clean the whole thing out. Again it was a cost thing - I was working my way through college and funds were very limited.

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    tvfinak:

    An “ideal world” would have to include Cast Bullets, because they have some real advantages over jacketed bullets.

    There is less friction, and therefore at the same pressure, the velocity will be higher, and reportedly, they won’t wear your barrel nearly to the extent that jacketed bullets do.

    Hard Cast bullets penetrate better for those applications where penetration is more prudent than expansion would be.

    And, of course, Cast Bullets allow us to shoot older firearms, and replicas of older firearms that were designed for cast bullets.

    Sure, they’re cheaper, but IMO, that is a minor thing compared to the other advantages.

    I have Cast Performance bullets in 44, and 357 on hand, and the Gas Checks are the same diameter as the bullets are.

    This is also true with the 44 caliber Gas Checked bullets I got from Stoner, at the last Gun Show hereabouts, and the 357 caliber Gas Checked bullets, I got from Arnies Bullets, same time, same place. I’m talkin .432, and .359 I don’t know what brand of Gas Checks that were used in any of the bullets I have.

    I’ve recovered both Oregon Trail and Meister 357 caliber bullets that had damage from gas cutting/blow by, and have had leading in my barrel from using them. These bullets are so hard, they won’t obturate that well, I guess.

    I have some OT, 30-30 bullets, too, and in my very non-scientific penetration tests, through magazines and catalogs, at 30-30 velocities, they had a tendency to crumble, rather than expand. Those bullet had Gas Checks too, but I hadda put’em on myself, and size them.

    They penetrated the same distance as the same weight jacketed bullets, but like I said, they crumbled, and I mean beeg time. Now, I have some softer 30-30 bullets, that I hope won’t shatter.

    I love cast bullets for the purpose they were intended for, and I look up to, those who can handload them successfully. It seems like anyone can load jacketed bullets, but Cast Bullets require a little more know how.

    Murphy’s dissertation on the subject was so good, that I saved it for future reference.

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    If you have a mold that produces a bullet with a base designed for gas checks, can you use ANY brand of gas checks? Or do specific molds or bullet designs require a particular type or brand of gas check?

    Thx,

    Brian

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    Default Gas Checks or no Gas Checks

    Smiity-

    Agreed! - cast bullets are great for many reasons only one of which is cost. I was primarily addressing the economic issue - I should have stated that in an idea world we would only shoot gas checked cast bullets

    I've got dozens of molds and sizing dies in calibers from .22 to .58 including some like the .43 Spanish were jacketed bullets aren't readily avaliable. Cast bullets also allow me to shoot casually plink with my .458s and .375s - economics here again.

    I would bet that your gas cut bullets were shot with pretty hot loads - I've never seen it at low and medium loads. As Murphy pointed out all sorts of nasty stuff happens at high pressures and high velocities. Where high begins has many variables as we all know.

    I'll stand by my statement that you generally don't need gas checks on cast bullets made for gas checks at lower velocity i.e. light loads and may or may not need them at moderate velocities. For hot loads I agree they are required.

    I'll dig out some more gas checks and bullets and get some more data in a later posting.


    Quote Originally Posted by Smitty of the North View Post
    tvfinak:

    An “ideal world” would have to include Cast Bullets, because they have some real advantages over jacketed bullets.


    Smitty of the North

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    Default Brands of gas checks

    All my bullet molds work with both the Lyman and Hornady gas checks.

    The Hornady gas checks are thicker at the open edge and larger in diameter than the bore size. When you run the bullet and gas check though the sizer they lock onto the bullet by swaging the top edge into bullet.

    Lyman gas checks are thinner and smaller than bore diameter. After sizing the bullet the Lyman checks can usually be removed with your thumbnail or sometimes they stick to the bottom of the sizing die punch if it has any excess lube on it.

    I understand that some accuracy shooter perfer the Lyman gas checks but I'll have to do some more research on this.

    Quote Originally Posted by tananaBrian View Post
    If you have a mold that produces a bullet with a base designed for gas checks, can you use ANY brand of gas checks? Or do specific molds or bullet designs require a particular type or brand of gas check?

    Thx,

    Brian

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    Default Gas Checks and paper patch bullets

    I totally forgot about paper patched cast bullets! These have been around forever and are still popular in some cast bullet target circles.

    For those that are unfamilar with them paper patched bullets are cast bullets with a paper jacket of banknote or other tought paper wrapper around them. No gas check or other protection for the base of the bullet at all - just plain old paper.

    Compared to any alloy of lead bullets paper is a very fragile material yet these bullets perform well up to some pretty decent velocities. The paper DOES NOT catch on fire or gas cut and the bullets are quite accurate. Agreed these are shot in rifles but the orginal post just said heavy bullets which I assumed could be either rifle or pistol.

    I'm sure there is a limit on the loads but for low to medium velocities with generally heavy bullets they work very well.

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    Quote Originally Posted by tvfinak View Post
    All my bullet molds work with both the Lyman and Hornady gas checks.

    The Hornady gas checks are thicker at the open edge and larger in diameter than the bore size. When you run the bullet and gas check though the sizer they lock onto the bullet by swaging the top edge into bullet.

    Lyman gas checks are thinner and smaller than bore diameter. After sizing the bullet the Lyman checks can usually be removed with your thumbnail or sometimes they stick to the bottom of the sizing die punch if it has any excess lube on it.

    I understand that some accuracy shooter perfer the Lyman gas checks but I'll have to do some more research on this.

    Gas checks are different. I haven't installed any gas checks in about 5 years and things may have changed a bit. Lyman gas checks of old were made for Lyman molds. There is a diminsional consideration of the base of the bullet and the thickness of the gas check. Hornady now seem to be the more prolific and easier to find. The old Lyman gas checks were made of what was known as gilding (bullet jacket material) metal an alloy of copper and zink (vs cupronickel of copper and nickel) these are harder and thinner I still have some of these and they are tough to bend with the thumb nail. The Hornady checks are thicker and softer. Also Lyman made crimp on and I guess push on (they had no crimp lip to bite into the bullet base) I never liked the push on type, they came of easily and I mainly used the crimp ons. I do believe that both Hornady and Lyman make all copper gas checks of the same thickness/hardness now. Commercial makers that I have asked have told me they use Hornady. I have some Saeco and Lyman molds for gas checked bullets and those were the last gas checks I installed on and I still have a quantity (over 5 000) of Lyman checks. They fit the bullets quite well and crimp on to the bullet and will still be there after recovery of the bullet in the dirt.

    As for the size, they are punched and cupped and left flared to greater than needed diameter so they wll fit over the base then are crimped down to sizing die diameter. They have to be larger than diameter before crimped on and just the sizer top punch pressure will form them to fit the die.

    Some lube-sizers used a gas check seater that was below the sizer, I think those were for the push on type. The older Lyman sizer I think was this way. The newer Lyman 450 lube-sizer and the Saeco that I have have a swingout gate above the sizing die and the check goes through the die . If I remember these machines correctly.

    Then when hit in the arse with even 15,000 psi the gas checks tend to flatten out and spread out and seal the base of the bullet to stop the flow of gas (or check the flow of gas) and prevent erosion and melting (remember 600 degrees F) of the alloy. That is there purpose and that is what they are supposed to do. As with all things success is to be measured. I do know the higher the pressure the better they work and the harder the bullet the more they are needed and when the bullet is slightly undersized there use can save the day for sure by making a seal.
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    Default Gas checks or no gas checks

    I did some more research on line and found this site that offers some pretty good info on all aspects of casting bullets:


    The authoer makes an interesting statement that I've head many times before in the past 45 years since I started casting bullets: "no one knows for certain exactly how gas checks work".

    I did some more research on paper jacketed bullets - now I gotta try them - and found that shooters are driving them up to 3000 fps. Recovered bullets show the paper bases intact. I find it a bit hard to believe that the base of a lead bullet will actualy melt without a gas check if the paper on these full power loads doesn't even get burnt. While the burning powder is indeed hot the exposure is so short the base of bullet just doesn't get that hot from the flame- kinda like passing your hand rapidly through a flame.
    Last edited by Murphy; 03-09-2008 at 16:17.

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    tvfinak:
    My loads were really not hot loads, and it is my understanding that this was likely the cause of the leading. Hard bullets would be less apt to obturate with a light load, versus a hot load. Murphy mentioned that, in the post I saved.

    This is not to say that using light loads with very hard cast bullets will necessarily cause leading.

    Those OT Lazer Cast bullets are made in machines, and have a bevel base, and no gas check. I couldn’t find the post, but I’m pretty sure that Murphy made them work for him recently. I’ve also read in a magazine that they can be accurate, and the price is right too. I’m not saying they are unsuitable for all purposes. I’m just relating my experiences.

    I usta think that the solution to leading was to use a harder bullet, until I read an article in a Wolfe Publications magazine (Handloader) by Brian Pierce, that explained the gas cutting/blow-by issue.

    As to gas checks, I like them, and I’m willing to pay more for them than plain base cast bullets, although I use both kinds.

    Thanks
    Smitty
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    The biggest source for leading with any lead bullet is gas getting past the bullet around the sides, just as it does with jacketed bullets. That's why proper fit is so important and a bore of uniform size for the length of the barrel so the bullet can be made to fit.

    Also with a revolver the fit to the throats is important and the throats must be matched to the bore. For a high pressure magnum revolver, the throats should be about .0015" to .002" larger than bore and bullets should be sized to fit the throats. For loads of a more moderate nature the bullet size can be about .001" larger than bore and the throats need to be sized accordingly, to fit the bullet. (431" throats, .431" bullets, .430" bore) This makes a tight fit in the bore and there is virtually no leading except the small amout from the open base of un gas checked bullets. This is usually at the forcing cone and first inch of the barrel. Gas checked bullets very definately reduce throat and forcing cone leading in revolvers.

    Brian is inquiring generically but he has a big bore high pressure revolver so most of my answers were along those lines and most of my lead bullet experience and studies are with revolvers.

    You mentioned the gas check on the 30 carbine load necessary to prevent the lead from clogging the gas port, that is exactly what it is supposed to do. The bore fit is certainly the same for gas checked or plain base but the sheilding effect the copper check has is what keeps the small amount of lead out of the port.

    Probably the most effective use of a gas checked bullet is with hard cast bullets (BHN 21) shot at pressures to low to obturate the bullet. At these moderate to maximum magnum loads, obturation may not effectively seal the bore even when properly sized, but a gas check will help. The gas check is also very beneficial when the bullet is slightly under sized for our bore diameter.

    If you take the BHN number and multiply by 1440 it will give the pressure needed to start the bullet to obturate. Forty four mag operating pressure is max at about 36,000 psi. We do run it much hotter however.

    As for paper patched bullets an interesting study but the bullet doesn not touch the bore. The bullet is not hard, (usually pure lead or 20:1) and the propellant is usually a very cool burning, low pressure black powder. I know very little about paper patch bullets and am not aware of any high pressure smokeless loadings that push to 3000 fps but that may be the case. The bullet does not touch the barrel and the base is rebated to fit in the case. Everything about that is different from hard cast gas checked bullets. I have shot my Sharps 45 2 7/8" with them but am not skilled in their use so I'll tip my hat to you on that subject.
    Last edited by Murphy; 03-09-2008 at 16:18.
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    Default How gas checks may work?

    Smitty-

    If you got leading with moderate loads you probably need a gas check. As I discussed in my first post you may or may need gas checks with moderate loads. Bullet composition and lube make a lot of difference also.

    The point I was trying to make is: TRY IT AND SEE what happend. Hard and fast rules with cast bullets are few and far between. No one is going to mess up a gun firing a few hunded moderate cast bullets loads through it trying something out to see is it will work or not!

    I think we can safely discount the powder charge melting the base of the bullet - remember the paper patch bullets. Gas cutting of sealing surfaces is an interesting topic. 600 psi steam will cut though the seats on a relief valve it ever begins to leak even though the seats are tungsen carbide. I'm not certain the gas check is a better seal than the lead - at high pressures gas can cut through any material. The statement of "not certain exactly how gas checks work" I think is a very true statement. No one has presented me with a clear explaination yet where I couldn't find technical holes in it.

    With a properly sized bullet in a rifle or SS pistol I don't think you will ever get blow by unless something wierd is going - too long of throat etc. A revolver is a much more complex device. If the cylinders are too large for the bullet you could certainly get gas blowby before it hits the rifling. Then we have the cylinder gap and forcing cone to deal with.

    I've found small bores like a .357 tends to lead more than my .44 mags with all other things being equal. Not sure why this was- I just stopped shooting the .357.

    One thing to consider with commercially cast bullers - Laser cast or others - is that they use a very hard lube for easy in shipping, handling, and commercial loading. I've recovered a lot of bullets out of the back stop that still had the lube intact - it couldn't have had much lubricating in the barrel. The old tried and true Alox and beeswax is much softer and comes off the bullets in shipping and handling - and probably much better. Someday I've got to buy some commercial bullets, remove the hard lube - and relube with the alox- beeswax blend. My guess it that they will be a better bullet with the softer lube.

    Along the lines of bullet lubes - ever shoot an totally un-lubed bullet in a dry clean bore? You generally get a really nasty heavily leaded bore. The importance of the lube sometimes get overlooked. I suspect some of the leading issues attributed to gas blowby / cutting may actually be lube problems. Could I talk you into repeating the loads you mentioned with alox/beeswax replacing the commercial hard lube and see what happens? Or let me know what you were shooting and I'll try and duplicate it.


    Quote Originally Posted by Smitty of the North View Post
    tvfinak:

    My loads were really not hot loads, and it is my understanding that this was likely the cause of the leading.
    Thanks
    Smitty

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    Default Gas checks and more

    I can find nothing in thsi thread before yours to tell me that Brian was shooting a revolver. When he said heavy cast bullets I assumed a rifle but mot of what I said applies to either. Perhaps you may also know that he was shooting eavy loads. Its hard to reply to a request for information unless you have some facts.

    While paper patched bullets were orginally used with black powder shooters are driving them near jacketed bullet velocities with full loads of smokeless powders. The paper doesn't even get charred! We have the same thing with plastic overpower wads in shotguns - they don't melt down and shotgun powders are hot double based powder. While they are at lower pressures and velocities they also stay in the bore longer exposed to the hot gases. Interestingly enough the bullets don't gas cut either even with only a paper seal between the bullet and the bore.

    The leading in the M2 gas clyinder was worse with plain based bullets but also occured with GC bullets. Leading can also show up the in the gas cylinder of M1 rifles. Not sure exactly what is happening unless the gas port shears a small chunk off the bullet.

    We can theorize all over the place but I think the old statement that "we don't know exactly how gas checks work" still applies. Unless you are aware that Brian only intended to shot heavy loads my orginal advice of "try it and see' still stands.


    [quote=Murphy;225600]Ya know, we didn't say it would burn away the bullet to where it would be unrecognizable. We said at tempertures as high as 3000 F it would melt some of the base and stick it to the bore.

    Brian is inquiring generically but he has a big bore high pressure revolver so most of my answers were along those lines and most of my lead bullet experience and studies are with revolvers.

    You mentioned the gas check on the 30 carbine load necessary to prevent the lead from clogging the gas port,


    As for paper patched bullets an interesting study but the bullet doesn not touch the bore. The bullet is not hard, (usually pure lead or 20:1) and the propellant is usually a very cool burning, low pressure black powder.

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    tvfinak:
    I've either shot, or loaded them all by now. The leading wasn't/isn't bad, and so they were not a waste.

    I suppose, it's possible that the damage I saw wasn't from gas-cutting, but from passing through the media, or something else, and my conclusion was influenced by what I had read.

    And yeah, that lube is hard enough for some of it to stay on the bullet.

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  19. #19

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    I'll chuck a monkey wrench into the workings here.

    Granted, I haven't done any of the math and can't find the articles I seem to remember reading but here is the general idea. I'm throwing this out there for you to chew on.

    Burning powder doesn't have enough heat to melt the base of a bullet as conventional wisdom suggests.

    As I remember the argument goes something like this.

    The specific heat of combusting powder or any other gas is low. Specific heat is the amount of energy per unit mass to raise the temerature of a substance by a degree Celsius. The meaning of all that is that while the temperature of the combusting gasses is very high, they contain very little energy that can be transfered in the form of heat. You can go sit in a sauna that is 160 degrees for quite awhile and not burn yourself. Spill 160 degree water on yourself you're headed for the burn ward. Water has a much higher specific heat than air.

    Lead is also an efficient conductor. It easily transfers heat throughout its mass. So when you apply heat to one part of a bullet it dissipates that heat throughout the rest of the bullet. You would have to heat the bullet up to near it's melting point before the combustible gasses would melt the base.

    If all this holds then bullet-barrel friction is a much more significant source of heat than propellant gasses.

    Usually in these sort of things the truth lies somewhere in the middle. This part is completely conjecture on my part so make sure it gets properly attributed if it is ever published. :P I did some brainstorming and the only way I could really think of to get leading close to the chamber, before the bullet has been subjected to large amounts of friction would be a multi-step process. If you do not subject a bullet to sufficient pressure to cause obturation through ductile flow then presumably it might still be acting in a more brittle manner. Break off pieces of lead small enough to be melted by the gas as it is combusting then you would end up with small molten lead globs entrained in the gas. When these globs hit the much cooler barrel surface it would cause them to instantly resolidify or freeze.

    On the paper patched bullet comment. You need oxygen for burning to happen. I've got a cheap walmart teapot that has heated untold gallons of water that still has an intact, unburned, still scanable bar code tag on the bottom. I'd guess that there isn't enough oxygen for the paper patches to burn while going down the barrel.

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    Quote Originally Posted by tvfinak View Post
    I can find nothing in thsi thread before yours to tell me that Brian was shooting a revolver.<snip>
    Murphy just happens to know that I have a new S&W 500 w/4" barrel and am diving into reloading, casting, and all that fun stuff... I guess that I should've mentioned which gun my questions pertained to.

    Brian

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