03lover
02-10-2010, 04:17 PM
Bore Leading Problem Caused By?
Like many reloader shooters, I have had my share of bore leading. The problem as most of us that deal with leading problems know, there can be a number of causes and at times more than one cause at a time making the solution to the problem difficult to resolve.
There is a list of the common causes of bore leading that we tend to follow in an attempt to eliminate the leading. I will not get into the established list of causes that most of us are well aware of. What I want to do is introduce the readers to a cause that is most often overlooked and the calibers most affected by this least known cause of leading and poor accuracy.
My worst experience with bore leading has been with the 9mm Luger. The next has been with my 38 Super. I see on many of the forums dealing with bore leading, the 9mm is one of the worst and many replies come back saying, “I shoot the 45 ACP with thousands of rounds of lead and have no problems.” The 45 ACP is actually very different from the 9mm.
Now for the cause of the problem. Cast or swaged lead bullets are being swaged down to a diameter that is less than the bullet diameter was before seating. We work hard to choose a bullet diameter that is properly fitted to the gun, cylinder throats, groove diameter of the bore, only to have that diameter reduced by the shell casing it is seated in. Please read on because this is a very real problem with some cartridges. You can perform your own test to see just how much of a problem it is for you with your loading process and components. You sort out the different brands of brass you load. Then process the brass as you normally do and without primer or powder seat and crimp your bullets as you normally do. Now pull those bullets and measure them, base and upper portion. I am sure with some brands of brass you will be very surprised.
There are a couple of reasons for that. The 9mm operates at about twice the pressure of the 45 ACP and the 38 Super is even higher pressure. The cause of the problem? The 9mm and the 38 Super, because of the pressure levels they operate at require the wall thickness and or the hardness of the brass to be thicker or harder to withstand those pressures. These cartridges also have a taper inside, getting progressively thicker as you get nearer to the base. In my case when I seated a cast bullet cast from wheel weights and 2% tin, when the bullets were pulled, I found the diameters had been reduced by .001” to as much as .003”. Often this reduction in diameter was greater at the base of the bullet than the portion at the case mouth. The longer the bullet or the deeper they are seated into the shell casing the greater the problem. A secondary cause of bullets being reduced in diameter during the loading process is the use of the Lee Carbide Crimping Die. If when using this die, there is any real sizing done, the bullet will be reduced in diameter and this can lead to bullet set back during the auto loading cycle because the bullet does not spring back as much as the harder brass causing less bullet retention in addition to leading the bore. I do like the Lee die, but not as a final resizing of the loaded round If there is a problem with chambering, I fix it so use of the Lee die is not necessary.
The 45 ACP is not immune to the problem, but is not near so bad as the other short cased pistol rounds. I would guess the 40 S&W and a few other calibers would experience this problem also.
I took three different brands of 9mm brass, Winchester, R-P an FC and processed it as I always do, seated a .355” diameter jacketed bullet and taper crimped to remove any bell. Then I measured the outside diameter of the rounds where the bullet is inside the shell casing. I found with the brass I have, the diameter varied from the smallest to largest, .003”. That means is my case, the R-P brass is .0015” thicker per side that the FC brass which is the thinnest.
Without boring the readers to death, I found the FC brass being thinner worked best for my cast bullets sized at .3565” to .357” diameter. With my 9mm and 38 Super I played with the different sizing dies I have and expanders to come up with the combination that provides good bullet retention without reducing cast bullet diameter. Not all sizing dies or expanders are equal. For jacketed bullets in the 9mm, I prefer the R-P brass and .355” bullets for good bullet retention.
Long pistol cartridges like the 38 Special, 357 Magnum or the 45 Colt have enough give in the case that seating a cast or swaged bullet rarely causes a reduction in bullet diameter. Too much taper crimping or use of the Lee Carbide Factory Crimp Die can mess things up. Being aware this can be a problem will help the reloader avoid being the cause of a leading or poor accuracy problem.
Like many reloader shooters, I have had my share of bore leading. The problem as most of us that deal with leading problems know, there can be a number of causes and at times more than one cause at a time making the solution to the problem difficult to resolve.
There is a list of the common causes of bore leading that we tend to follow in an attempt to eliminate the leading. I will not get into the established list of causes that most of us are well aware of. What I want to do is introduce the readers to a cause that is most often overlooked and the calibers most affected by this least known cause of leading and poor accuracy.
My worst experience with bore leading has been with the 9mm Luger. The next has been with my 38 Super. I see on many of the forums dealing with bore leading, the 9mm is one of the worst and many replies come back saying, “I shoot the 45 ACP with thousands of rounds of lead and have no problems.” The 45 ACP is actually very different from the 9mm.
Now for the cause of the problem. Cast or swaged lead bullets are being swaged down to a diameter that is less than the bullet diameter was before seating. We work hard to choose a bullet diameter that is properly fitted to the gun, cylinder throats, groove diameter of the bore, only to have that diameter reduced by the shell casing it is seated in. Please read on because this is a very real problem with some cartridges. You can perform your own test to see just how much of a problem it is for you with your loading process and components. You sort out the different brands of brass you load. Then process the brass as you normally do and without primer or powder seat and crimp your bullets as you normally do. Now pull those bullets and measure them, base and upper portion. I am sure with some brands of brass you will be very surprised.
There are a couple of reasons for that. The 9mm operates at about twice the pressure of the 45 ACP and the 38 Super is even higher pressure. The cause of the problem? The 9mm and the 38 Super, because of the pressure levels they operate at require the wall thickness and or the hardness of the brass to be thicker or harder to withstand those pressures. These cartridges also have a taper inside, getting progressively thicker as you get nearer to the base. In my case when I seated a cast bullet cast from wheel weights and 2% tin, when the bullets were pulled, I found the diameters had been reduced by .001” to as much as .003”. Often this reduction in diameter was greater at the base of the bullet than the portion at the case mouth. The longer the bullet or the deeper they are seated into the shell casing the greater the problem. A secondary cause of bullets being reduced in diameter during the loading process is the use of the Lee Carbide Crimping Die. If when using this die, there is any real sizing done, the bullet will be reduced in diameter and this can lead to bullet set back during the auto loading cycle because the bullet does not spring back as much as the harder brass causing less bullet retention in addition to leading the bore. I do like the Lee die, but not as a final resizing of the loaded round If there is a problem with chambering, I fix it so use of the Lee die is not necessary.
The 45 ACP is not immune to the problem, but is not near so bad as the other short cased pistol rounds. I would guess the 40 S&W and a few other calibers would experience this problem also.
I took three different brands of 9mm brass, Winchester, R-P an FC and processed it as I always do, seated a .355” diameter jacketed bullet and taper crimped to remove any bell. Then I measured the outside diameter of the rounds where the bullet is inside the shell casing. I found with the brass I have, the diameter varied from the smallest to largest, .003”. That means is my case, the R-P brass is .0015” thicker per side that the FC brass which is the thinnest.
Without boring the readers to death, I found the FC brass being thinner worked best for my cast bullets sized at .3565” to .357” diameter. With my 9mm and 38 Super I played with the different sizing dies I have and expanders to come up with the combination that provides good bullet retention without reducing cast bullet diameter. Not all sizing dies or expanders are equal. For jacketed bullets in the 9mm, I prefer the R-P brass and .355” bullets for good bullet retention.
Long pistol cartridges like the 38 Special, 357 Magnum or the 45 Colt have enough give in the case that seating a cast or swaged bullet rarely causes a reduction in bullet diameter. Too much taper crimping or use of the Lee Carbide Factory Crimp Die can mess things up. Being aware this can be a problem will help the reloader avoid being the cause of a leading or poor accuracy problem.