I often see Montana Gold bullets advertised, where they have a choice of the same weight bullet, but in either CMJ or FMJ. Now, I understand the difference between Complete Metal Jacket and Full Metal Jacket, but does one have any advantage over the other in the same pistol?
Question re: CMJ vs FMJ
- Thread starter Six Star
- Start date
Marstar's site had this to say:
The main difference between 'Complete Metal Jacketed' (CMJ) bullets - sometimes called 'Total Metal Jacketed') and the traditional 'Full Metal Jacket' (FMJ) is the manufacturing process used. FMJ projectiles are manufactured by pressing the lead core into the jacket while the jacket of the CMJ projectile is electroplated directly onto the lead core, completely covering the projectile including its base.
There are many advantages to CMJ bullets: they are lead safe both to handle and shoot (no dangerous lead vapour after firing and no lead fouling in the bore) and they are more economical to produce than traditional FMJ projectiles while retaining all the performance associated with traditional FMJ bullets.
The main difference between 'Complete Metal Jacketed' (CMJ) bullets - sometimes called 'Total Metal Jacketed') and the traditional 'Full Metal Jacket' (FMJ) is the manufacturing process used. FMJ projectiles are manufactured by pressing the lead core into the jacket while the jacket of the CMJ projectile is electroplated directly onto the lead core, completely covering the projectile including its base.
There are many advantages to CMJ bullets: they are lead safe both to handle and shoot (no dangerous lead vapour after firing and no lead fouling in the bore) and they are more economical to produce than traditional FMJ projectiles while retaining all the performance associated with traditional FMJ bullets.
CMJ's are considered "lead free." this is becuase with the lead covered, there is no lead to vaporize as the bullet leaves the gun. Lead starts to vaporize when bullets are traveling at plus 1000 FPS. so if you are shooting a firearm indoors, with a bullet moving faster then 1000 FPS, using CMj's will expose you to less lead in the air.
Walter Hornby: "Lead starts to vaporize when bullets are traveling at plus 1000 FPS."
Horse Hocky! Where did you get this gem from? The biggest factor in lead exposure in indoor ranges is from the primers not lead bullets. The smoke you get from shooting lead is from the bullet lube. The boiling point of lead is over 3200 degrees F
You ever shoot a 30-06 with lead bullets?
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Horse Hocky! Where did you get this gem from? The biggest factor in lead exposure in indoor ranges is from the primers not lead bullets. The smoke you get from shooting lead is from the bullet lube. The boiling point of lead is over 3200 degrees F
You ever shoot a 30-06 with lead bullets?
Stay Safe
There are parts of this I agree with and parts I don't. True, lead does boil at about 3200 degrees F, but it starts to vapourize at its melting temperature (albeit exceedingly little) which is about 600 F. The boiling point is simply the temperature at which its vapour pressure equals atmospheric pressure. Water, for example vapourizes quite rapidly well below its boiling point, otherwise we'd have no rain.
It seems reasonable then that the temperatures created by combustion and friction would create some lead vapour from the bullet - how much is debatable, but likely very, very little. Problem with indoor shooting is, you get an enclosed enough space, sufficient guns, and a sufficiently long period of exposure, and you could get a measurable increase in blood lead levels.
The smoke from cast bullets is from burning powder and lube, not lead vapour.
True, primers do (did?) contribute lead, but I didn't know that primers were still sold that contained lead. If so, which ones? Many ranges banned the use of primers with lead some time ago.
Lead is not absorbed by the skin - it must be ingested (swallowed or breathed in). The greatest concern for shooters should be ingestion from handling lead and then having the lead on their hands transferred to their mouths. Thorough washing after handling is a must. Breathing fumes is a hazard that just won't be encountered by shooters at levels that are measurable, even when casting.
It seems reasonable then that the temperatures created by combustion and friction would create some lead vapour from the bullet - how much is debatable, but likely very, very little. Problem with indoor shooting is, you get an enclosed enough space, sufficient guns, and a sufficiently long period of exposure, and you could get a measurable increase in blood lead levels.
The smoke from cast bullets is from burning powder and lube, not lead vapour.
True, primers do (did?) contribute lead, but I didn't know that primers were still sold that contained lead. If so, which ones? Many ranges banned the use of primers with lead some time ago.
Lead is not absorbed by the skin - it must be ingested (swallowed or breathed in). The greatest concern for shooters should be ingestion from handling lead and then having the lead on their hands transferred to their mouths. Thorough washing after handling is a must. Breathing fumes is a hazard that just won't be encountered by shooters at levels that are measurable, even when casting.
Canuck44 said:
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Andy
From what I understand most of the primers on the market contain lead. Can't tell you which ones are now lead free. A google search should answer the question.
This whole issue of lead ingestion is way overstated IMHO. I say that because there are people around who have shot indoors on the old ranges for years without any undue effect. Lead can't be absorbed by the skin. Use common sense when handling lead and by all means shoot at well ventalated indoor ranges but lets not become chicken little here the sky isn't falling.
Lead vapours from bullets travelling through a barrel is beyond the twi-light zone. For that matter so is the notion that lead is melted off the base of a lead bullet upon firing. A bullet leaving a 5" 1911 .45acp at 810 fps is in the barrel for 77/1000 of a second. Less time if you want to consider a 9mm lead bullet travelling out of a 5" barrel at 1,100 fps. Hardly time for the vapourization or melting to occur. I won't say it can't happen just doesn't reason out when you look at recovered fired bullets and the physics involved.
One way to close ranges and discourage shooting sports is to put in place expensive regulations regarding air quality, etc which small ranges cannot comply with.
I have reloaded and shot all my life, my one wish when I am in my 80's and lying quietly in a hosptal bed is not to die from nothing....
Don't think your water vapour analogy holds up. WE are talking about a metal here not a compound. Melting lead is one thing but there is a significant gap between the melting point and boiling point of lead vs ice/water/steam.
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From what I understand most of the primers on the market contain lead. Can't tell you which ones are now lead free. A google search should answer the question.
This whole issue of lead ingestion is way overstated IMHO. I say that because there are people around who have shot indoors on the old ranges for years without any undue effect. Lead can't be absorbed by the skin. Use common sense when handling lead and by all means shoot at well ventalated indoor ranges but lets not become chicken little here the sky isn't falling.
Lead vapours from bullets travelling through a barrel is beyond the twi-light zone. For that matter so is the notion that lead is melted off the base of a lead bullet upon firing. A bullet leaving a 5" 1911 .45acp at 810 fps is in the barrel for 77/1000 of a second. Less time if you want to consider a 9mm lead bullet travelling out of a 5" barrel at 1,100 fps. Hardly time for the vapourization or melting to occur. I won't say it can't happen just doesn't reason out when you look at recovered fired bullets and the physics involved.
One way to close ranges and discourage shooting sports is to put in place expensive regulations regarding air quality, etc which small ranges cannot comply with.
I have reloaded and shot all my life, my one wish when I am in my 80's and lying quietly in a hosptal bed is not to die from nothing....
Don't think your water vapour analogy holds up. WE are talking about a metal here not a compound. Melting lead is one thing but there is a significant gap between the melting point and boiling point of lead vs ice/water/steam.
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You can buy ammo that have leadfree primers, but they are not sold as components.
When I was in the army, I had to get blood tested for lead on a relatively regular basis, I never had any unsafe levels but the confirmation was nice to have. It doesn't take a lot of exposure to elevate to hazardous levels and it takes a long time for your body to flush it out.
Pat
When I was in the army, I had to get blood tested for lead on a relatively regular basis, I never had any unsafe levels but the confirmation was nice to have. It doesn't take a lot of exposure to elevate to hazardous levels and it takes a long time for your body to flush it out.
Pat
Horse Hocky! Where did you get this gem from? The biggest factor in lead exposure in indoor ranges is from the primers not lead bullets. The smoke you get from shooting lead is from the bullet lube. The boiling point of lead is over 3200 degrees F
You ever shoot a 30-06 with lead bullets?
Stay Safe[/QUOTE]
i never said that the ONLY source of vaporized lead is from the bullet. i just said that lead starts to vaporize over 1000 FPS. the amount is very negligible for indoor shooting as is the primer amount, through the primer is more. most problems with lead indoor is hand to mouth. however the thread was on what was the difference. which i replied to.
as a side note, pure lead bullets will "break apart" if pushed to fast. thats why most bullets have a metal jacket.
You ever shoot a 30-06 with lead bullets?
Stay Safe[/QUOTE]
i never said that the ONLY source of vaporized lead is from the bullet. i just said that lead starts to vaporize over 1000 FPS. the amount is very negligible for indoor shooting as is the primer amount, through the primer is more. most problems with lead indoor is hand to mouth. however the thread was on what was the difference. which i replied to.
as a side note, pure lead bullets will "break apart" if pushed to fast. thats why most bullets have a metal jacket.
Yes and I said horse hockey to lead vaporizing at speeds over 1,000 fps and stand by it. Now you are saying lead bullets break apart when pushed to fast. If we are talking rifle and pistol velocities I have to return to horse hockey, sounds better than horse sh**t doesn't it. And who shoots pure lead bullets at speeds where they would "break apart"? Pure lead bullets if pushed to fast certainly will lead up your barrel but "break apart". Haven't seen that happen yet in 30 odd years of reloading but maybe....
I agree licking your fingers after handling lead or lead alloys is not smart and sure way of ingesting lead with resulting high lead concentrations in the body. Not good! A little common sense and any shooter will be fine. I personally would be more worried about the air I breathed if I lived in a large city or in the Fraser Valley more than I would be concerned about lead exposure from a ventalated indoor shooting range.
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I agree licking your fingers after handling lead or lead alloys is not smart and sure way of ingesting lead with resulting high lead concentrations in the body. Not good! A little common sense and any shooter will be fine. I personally would be more worried about the air I breathed if I lived in a large city or in the Fraser Valley more than I would be concerned about lead exposure from a ventalated indoor shooting range.
STay Safe
I shoot a 38 super in IPSC shooting at major factor(115 gr @ 1420fps).Initially I used a FMJ MG bullet(as it was a little cheaper),but found that the exposed base deposited lead in the compensator,which took lots of patient scraping with a sharp tool to remove,the lead sort of solders itself on,I now only use CMJ bullets,they are a little more expensive,but worth the hassles of a clogged up comp.
In my 9mm production gun I use the cheaper FMJ bullets and they work just fine.
In my 9mm production gun I use the cheaper FMJ bullets and they work just fine.
