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Lost Sheep · July 17, 2011, 02:16 PM

Welcome to the forum and welcome to reloading. You have asked good questions. They also show that you think before acting. Good for you.

COAL (Cartridge OverAll Length) The importance of the cartridge length is not so much the length of the cartridge (aside from making sure they cartridge can cycle through your action), but the length of the cavity under the bullet where the powder is. This is affected by how long the actual bullet/slug is as well as the cartridge overall length. If the particular bullet you are measuring has a longer nose than its brethren, you will get a smaller volume under the bullet and (if set to the same overall length) will have a smaller volume when the powder burns. Smaller volume means greater pressure.

Fortunately, handgun bullets are pretty uniform between bullets yo get from the same box. Handgun bullets are short and stubby. Spire point rifle bullets have more potential for variation. Fortunately, the bullet makers are generally VERY uniform.

The thickness of the web of your brass affects the under-bullet volume is also important, but is also pretty uniform in a given caliber. But if you are pushing up against the loading limits (either the high end or the low end) it would be wise to ensure all your brass came from the same maker. Federal brass is likely to have the same internal volume as other Federal brass, but may be different from Lake City or Winchester brass.

Leading is worse if you have an undersized bullet (hot gasses get past the sides of the bullet that does not completely seal the bore of your barrel, melting the lead on the bullets' sides and leaving it on the inside of your barrel).

Do a search on "Glock" and "lead". The conventional wisdom about polygonally rifled barrels is that leading is a problem with them. Then, the next time you shoot a jacketed bullet, it will tend to stick in the bore and cause ultra-high pressure. Do a search on "Glock Kaboom".

Glocks are not the only guns with polygonal barrels, but their popularity has gotten their name attached to the phenomenon. It is not a fault with the Glock.

There are aftermarket barrels with conventional rifling popular with Glock shooters who shoot lead bullets. Or, you can bring your cleaning kit with you to the range and periodically check your barrel for lead buildup. Or you can shoot copper plated bullets. They are only a little more expensive than lead and a lot less expensive than jacketed. Plated bullets take the load data from lead bullets.

On ultra-light loads: I just read an article from a fellow who was using an extremely light load in a large case. He blew up a Thompson-Contender (a VERY strong single-shot pistol). Apparently, because of the very small amount of powder in a very large case (he was fire-forming a 45-70 to a 475, .458 bullet diameter to .475" diameter). Several charges were OK and then one - disaster. Thankfully, no injuries.

The good firings were shot when the powder was at the back of the cartridge, near the primer. The last one, he had pointed the gun downward, then raised it up. This evidently left a huge air gap between the primer and the powder, leading to S.E.E. (Secondary Explosive Effect).

Interior ballistics is more art than science and, I suspect, even more guesswork than art. Even the experts have observed things that are very difficult to explain.

The recipes you find in the loading manuals have been pretty thoroughly vetted. Most shooters find it wise to stay within them even if they make no (apparent) sense until you dig deep enough. Sometimes it takes a laboratory to dig that deep, though.

Lost Sheep

July 17, 2011, 02:16 PM	#9
Lost Sheep Senior Member Join Date: January 24, 2009 Location: Anchorage Alaska Posts: 3,341	Expanding a bit on the COAL and Lead questions Welcome to the forum and welcome to reloading. You have asked good questions. They also show that you think before acting. Good for you. COAL (Cartridge OverAll Length) The importance of the cartridge length is not so much the length of the cartridge (aside from making sure they cartridge can cycle through your action), but the length of the cavity under the bullet where the powder is. This is affected by how long the actual bullet/slug is as well as the cartridge overall length. If the particular bullet you are measuring has a longer nose than its brethren, you will get a smaller volume under the bullet and (if set to the same overall length) will have a smaller volume when the powder burns. Smaller volume means greater pressure. Fortunately, handgun bullets are pretty uniform between bullets yo get from the same box. Handgun bullets are short and stubby. Spire point rifle bullets have more potential for variation. Fortunately, the bullet makers are generally VERY uniform. The thickness of the web of your brass affects the under-bullet volume is also important, but is also pretty uniform in a given caliber. But if you are pushing up against the loading limits (either the high end or the low end) it would be wise to ensure all your brass came from the same maker. Federal brass is likely to have the same internal volume as other Federal brass, but may be different from Lake City or Winchester brass. Leading is worse if you have an undersized bullet (hot gasses get past the sides of the bullet that does not completely seal the bore of your barrel, melting the lead on the bullets' sides and leaving it on the inside of your barrel). Do a search on "Glock" and "lead". The conventional wisdom about polygonally rifled barrels is that leading is a problem with them. Then, the next time you shoot a jacketed bullet, it will tend to stick in the bore and cause ultra-high pressure. Do a search on "Glock Kaboom". Glocks are not the only guns with polygonal barrels, but their popularity has gotten their name attached to the phenomenon. It is not a fault with the Glock. There are aftermarket barrels with conventional rifling popular with Glock shooters who shoot lead bullets. Or, you can bring your cleaning kit with you to the range and periodically check your barrel for lead buildup. Or you can shoot copper plated bullets. They are only a little more expensive than lead and a lot less expensive than jacketed. Plated bullets take the load data from lead bullets. On ultra-light loads: I just read an article from a fellow who was using an extremely light load in a large case. He blew up a Thompson-Contender (a VERY strong single-shot pistol). Apparently, because of the very small amount of powder in a very large case (he was fire-forming a 45-70 to a 475, .458 bullet diameter to .475" diameter). Several charges were OK and then one - disaster. Thankfully, no injuries. The good firings were shot when the powder was at the back of the cartridge, near the primer. The last one, he had pointed the gun downward, then raised it up. This evidently left a huge air gap between the primer and the powder, leading to S.E.E. (Secondary Explosive Effect). Interior ballistics is more art than science and, I suspect, even more guesswork than art. Even the experts have observed things that are very difficult to explain. The recipes you find in the loading manuals have been pretty thoroughly vetted. Most shooters find it wise to stay within them even if they make no (apparent) sense until you dig deep enough. Sometimes it takes a laboratory to dig that deep, though. Lost Sheep Last edited by Lost Sheep; July 17, 2011 at 02:30 PM.