There's been allot of discussion in this forum about pc'd bullets & cast bullets and will this or that work. Figured I'd talk a little bit on powder coated bullets (pc'd) and their traditional sized/lubed counterparts.
Traditional cast/lubed/sized bullets:
Typically a bullet was cast, then sized, then lubed. Casting the bullet was done from an alloy, alloys are nothing more than combo's of different metals making the lead harder or softer. Lubes are combo's of different oils, greases and waxes. Sizing the bullet is extremely important, the closer the fit, the better.
Putting it all together:
When a bullet is fired it becomes under pressure. The base of the bullet compresses from that pressure. When the base compresses it squeezes lube out of the lube groove. The least amount of resistance is forward. The lube goes sideways (against the bbl) until it can't anymore so it takes the path of least resistance, which is forward. The lube will also be pressurized from hot gasses coming by the bottom drive band. The pushing/pressurizing of this lube forward makes the lube act like a gasket. Not only is the lube protecting the bbl it is sealing off gasses from getting by any bbl imperfections that the front drive bands hit as the lube is forced forward.
Not my picture, it was sent to me from another website were I was having a discussion about bullet compression. He was testing round grease groove vs square in a 44mag.
If you look closely at the bottom groove/lube groove on those bullets you'll see different amounts of compression (bigger/smaller). What you want to see in a bullet is what you see with the bullet that is in the far right of the picture/ last bullet on the right. It shows mild base compression, good even crisp rifling marks the whole length of the bullet (no skidding). And the front drive bands look complete with crisp edges.
Sizing the bullet;
The closer the size of the bullet to the cylinders/bbl. The less the bullet has to seal as the base is compressed.
Alloy:
There's been formula's out there for this hardness/that hardness, yada/yada/yada. Most of them are telling you the minimum hardness for the pressure being used.
Lube:
I use 2 different lubes. The 1st lube is a soft lube that has more oil than wax. The 2nd lube has more wax than grease. 95%+ of the time I use the soft lube because the lube has to be able to flow out and forward for the bullet to function properly. Too hard of a lube and it will never flow/seal act like a gasket and bad things happen.
walking the line:
It's a juggling act between size/alloy/lube and if any one of them are wrong, nothing works and things like loss of accuracy and leading come into play. Too hard of an alloy and the base will not compress enough to push the lube into the front bands. Gasses will get by everything and and loss of accuracy and flame cutting/leading will happen. (That's why too hard of a bullet leads the bbl). Get the perfect alloy and use too hard of a lube and the same thing happens, the lube can't flow. No lube, no accuracy. At the end of the day the reloader has to do a balancing act to find the right combo of alloy/lube/pressure to make an accurate load. There's always wiggle room and sizing/alloys/or lubes will aid in masking problems if any of those things aren't ideal. But even then, everything has to be pretty much spot on. That's why when casters find a good load/bullet combo they treat it like gold. That's also why allot of shooter use the same loads for specific bullets. They work!!!
Pc'd bullets:
They use the same size/alloy/lube rules that traditional bullets are bound by. The pc'd bullets simply have the ability to use those same rules differently.
Alloy:
Instead of matching the alloy to the pressure, pc'd bullets match the alloy to the bullet design. The pc'd bullets can also be allot softer which aids in bumping/sealing the bbl.
Lube:
Pc'd bullets take any and all lube issues out of the picture. It's already everywhere it needs to be. No more too hard/too soft, not enough, the right pressure to seal everything.
Size:
Because pc'd bullets can be used with such a soft alloy, the correct sizing of the bullet is not a critical. The is no bullet base to compress to push the lube to form the correct seal/gasket. Seeing's how the lube is already in the correct places the soft alloy of the pc'd bullet can easily be bumped up by the pressure of the load to seal the bbl, hence accuracy.
How do we prove such things????
By using a chronograph. Take the same bullet, same size, same firearm, same load and shoot pc'd bullets vs traditional cast bullets. You'll find that the pc'd bullet will have more velocity for the same load. It isn't that the pc coating is slicker/oiler than the traditional lubes. It's that the bullet is sealing the bbl better/more efficient. Used to do the same thing with traditional cast/lubed bullets. I'd try 2 or 3 different alloys for the same sized/lubed bullet to see which 1 had the highest velocity. Once that was found I knew the correct alloy/pressure combo.
It isn't rocket science but allot of things have to happen to get a good load with traditional cast/sized/lubed bullets. When pc'ing 1st came out and people were perfecting how to pc their own bullets I was all ears. After some initial testing with high pressure rounds (308) I decided to give pc'd bullets a real test to see what they could really do.
I decided on using a 44mag for testing pc'd bullets. The 44's tend to be a bit pickier than the 38spl/357's (which I own 9 of and have had excellent result with for decades). Just wanted some plinking loads that woulkd do around 1 1/2" @ 25yds. Now I bought a beater 629 back in 2006/2008? and used molds/bullets that I've had from 30+years to a couple of years. I also used the same powders that I've tested loads/bullet combo's with in this pistol for several years. At the end of the day I found 2 loads with traditional cast/sized/lubed bullets with 5 different bullets and 6 powders that would meet the 1 1/2" @ 25yds. I redid the same testing with pc's bullets and ended up with 13 loads that would do the same 1 1/2" @ 25yds.
13 vs 2:
Same firearm, same molds that cast the bullets, same sizers, same reloading dies, same shooter, etc. The only difference is the bullet!!!
Pc'd bullets take any lube issues out of the equation. That's the difference between an accurate load and one that isn't. The only thing you're matching with pc'd bullets is the pressure of the load to the design of the bullet. Undersized bullet ='s more pressure to obturate the bullet to the bore.
Can you have more than 1 load for the same pc'd bullet???? Absolutely!!! Simply change powders, different push/amount of pressure applied between burn rates. It's nothing to get 6 or 7 different loads using the same pc'd bullet and different powders. The only real thing I've noticed with pc'd bullets is the thickness of the bullets bottom drive band plays a huge roll in how hard you can drive the bullet. Some bullet designs like these 429303's have a gc and 2 extremely small drive bands. You don't need a gc on this bullet with powder puff loads. But when you heat them up to full house loads the small bands will fail.
Well, that's my take on why pc'd bullets perform better than traditional cast/lubed bullets.
In a nut shell:
Traditional bullets have to have the right combo of alloy/pressure to have the correct lube flow to not only lube the bbl, but form a gasket to seal gasses/flame cutting of the bullet. Raise or lower the pressure and you have to start all over again.
Pc'd bullet's only have to rely on amount of pressure of the load to expand/seal the bbl for the size/design of the bullet. After the minimum pressure is reached to seal the bbl pressures can be increased until the design of the bullet fails.
Can you have more than 1 load for the same bullet with traditional cast/sized/lubed bullets??? Absolutely!!! But typically they are either close in their pressure range or the short start pressure of the load is soft enough to not distort the base of the bullet.
I'd like to see anyone using traditional cast/sized/lubed bullets use the same alloy/lube in several different calibers and run that their bullets at anything from 700fps (8,000psi) to 2400fps (50,000psi). Let alone maintain high accuracy levels.
Anyway, that's my take on pc'd bullets. Their just more forgiving.
Traditional cast/lubed/sized bullets:
Typically a bullet was cast, then sized, then lubed. Casting the bullet was done from an alloy, alloys are nothing more than combo's of different metals making the lead harder or softer. Lubes are combo's of different oils, greases and waxes. Sizing the bullet is extremely important, the closer the fit, the better.
Putting it all together:
When a bullet is fired it becomes under pressure. The base of the bullet compresses from that pressure. When the base compresses it squeezes lube out of the lube groove. The least amount of resistance is forward. The lube goes sideways (against the bbl) until it can't anymore so it takes the path of least resistance, which is forward. The lube will also be pressurized from hot gasses coming by the bottom drive band. The pushing/pressurizing of this lube forward makes the lube act like a gasket. Not only is the lube protecting the bbl it is sealing off gasses from getting by any bbl imperfections that the front drive bands hit as the lube is forced forward.
Not my picture, it was sent to me from another website were I was having a discussion about bullet compression. He was testing round grease groove vs square in a 44mag.
If you look closely at the bottom groove/lube groove on those bullets you'll see different amounts of compression (bigger/smaller). What you want to see in a bullet is what you see with the bullet that is in the far right of the picture/ last bullet on the right. It shows mild base compression, good even crisp rifling marks the whole length of the bullet (no skidding). And the front drive bands look complete with crisp edges.
Sizing the bullet;
The closer the size of the bullet to the cylinders/bbl. The less the bullet has to seal as the base is compressed.
Alloy:
There's been formula's out there for this hardness/that hardness, yada/yada/yada. Most of them are telling you the minimum hardness for the pressure being used.
Lube:
I use 2 different lubes. The 1st lube is a soft lube that has more oil than wax. The 2nd lube has more wax than grease. 95%+ of the time I use the soft lube because the lube has to be able to flow out and forward for the bullet to function properly. Too hard of a lube and it will never flow/seal act like a gasket and bad things happen.
walking the line:
It's a juggling act between size/alloy/lube and if any one of them are wrong, nothing works and things like loss of accuracy and leading come into play. Too hard of an alloy and the base will not compress enough to push the lube into the front bands. Gasses will get by everything and and loss of accuracy and flame cutting/leading will happen. (That's why too hard of a bullet leads the bbl). Get the perfect alloy and use too hard of a lube and the same thing happens, the lube can't flow. No lube, no accuracy. At the end of the day the reloader has to do a balancing act to find the right combo of alloy/lube/pressure to make an accurate load. There's always wiggle room and sizing/alloys/or lubes will aid in masking problems if any of those things aren't ideal. But even then, everything has to be pretty much spot on. That's why when casters find a good load/bullet combo they treat it like gold. That's also why allot of shooter use the same loads for specific bullets. They work!!!
Pc'd bullets:
They use the same size/alloy/lube rules that traditional bullets are bound by. The pc'd bullets simply have the ability to use those same rules differently.
Alloy:
Instead of matching the alloy to the pressure, pc'd bullets match the alloy to the bullet design. The pc'd bullets can also be allot softer which aids in bumping/sealing the bbl.
Lube:
Pc'd bullets take any and all lube issues out of the picture. It's already everywhere it needs to be. No more too hard/too soft, not enough, the right pressure to seal everything.
Size:
Because pc'd bullets can be used with such a soft alloy, the correct sizing of the bullet is not a critical. The is no bullet base to compress to push the lube to form the correct seal/gasket. Seeing's how the lube is already in the correct places the soft alloy of the pc'd bullet can easily be bumped up by the pressure of the load to seal the bbl, hence accuracy.
How do we prove such things????
By using a chronograph. Take the same bullet, same size, same firearm, same load and shoot pc'd bullets vs traditional cast bullets. You'll find that the pc'd bullet will have more velocity for the same load. It isn't that the pc coating is slicker/oiler than the traditional lubes. It's that the bullet is sealing the bbl better/more efficient. Used to do the same thing with traditional cast/lubed bullets. I'd try 2 or 3 different alloys for the same sized/lubed bullet to see which 1 had the highest velocity. Once that was found I knew the correct alloy/pressure combo.
It isn't rocket science but allot of things have to happen to get a good load with traditional cast/sized/lubed bullets. When pc'ing 1st came out and people were perfecting how to pc their own bullets I was all ears. After some initial testing with high pressure rounds (308) I decided to give pc'd bullets a real test to see what they could really do.
I decided on using a 44mag for testing pc'd bullets. The 44's tend to be a bit pickier than the 38spl/357's (which I own 9 of and have had excellent result with for decades). Just wanted some plinking loads that woulkd do around 1 1/2" @ 25yds. Now I bought a beater 629 back in 2006/2008? and used molds/bullets that I've had from 30+years to a couple of years. I also used the same powders that I've tested loads/bullet combo's with in this pistol for several years. At the end of the day I found 2 loads with traditional cast/sized/lubed bullets with 5 different bullets and 6 powders that would meet the 1 1/2" @ 25yds. I redid the same testing with pc's bullets and ended up with 13 loads that would do the same 1 1/2" @ 25yds.
13 vs 2:
Same firearm, same molds that cast the bullets, same sizers, same reloading dies, same shooter, etc. The only difference is the bullet!!!
Pc'd bullets take any lube issues out of the equation. That's the difference between an accurate load and one that isn't. The only thing you're matching with pc'd bullets is the pressure of the load to the design of the bullet. Undersized bullet ='s more pressure to obturate the bullet to the bore.
Can you have more than 1 load for the same pc'd bullet???? Absolutely!!! Simply change powders, different push/amount of pressure applied between burn rates. It's nothing to get 6 or 7 different loads using the same pc'd bullet and different powders. The only real thing I've noticed with pc'd bullets is the thickness of the bullets bottom drive band plays a huge roll in how hard you can drive the bullet. Some bullet designs like these 429303's have a gc and 2 extremely small drive bands. You don't need a gc on this bullet with powder puff loads. But when you heat them up to full house loads the small bands will fail.
Well, that's my take on why pc'd bullets perform better than traditional cast/lubed bullets.
In a nut shell:
Traditional bullets have to have the right combo of alloy/pressure to have the correct lube flow to not only lube the bbl, but form a gasket to seal gasses/flame cutting of the bullet. Raise or lower the pressure and you have to start all over again.
Pc'd bullet's only have to rely on amount of pressure of the load to expand/seal the bbl for the size/design of the bullet. After the minimum pressure is reached to seal the bbl pressures can be increased until the design of the bullet fails.
Can you have more than 1 load for the same bullet with traditional cast/sized/lubed bullets??? Absolutely!!! But typically they are either close in their pressure range or the short start pressure of the load is soft enough to not distort the base of the bullet.
I'd like to see anyone using traditional cast/sized/lubed bullets use the same alloy/lube in several different calibers and run that their bullets at anything from 700fps (8,000psi) to 2400fps (50,000psi). Let alone maintain high accuracy levels.
Anyway, that's my take on pc'd bullets. Their just more forgiving.
.
