BruceB
07-17-2006, 05:00 PM
An interesting occurrence came to my attention recently.
In my extensive cast-boolit shooting in the .308/7.62 NATO M1A, I discovered that the extended flash suppressor is giving me some indications about what might be happening to bullet lube once the bullet starts down the bore from the chamber.
We are all quite familiar with the "smokiness" of our cast loads, compared to the "normal" jacketed-bullet ammunition that sane people use. Based on the evidence derived from the flash suppressor, it's plain to see that a goodly proportion of the lube (Felix lube, in this case) is actually departing the muzzle as a vapor, not as a solid lubricant attached to the bullet.
I hasten to add that the lube is doing its job very well, because the rifle simply does NOT display bore leading with any load to date.
The forward half of the OUTSIDE of the suppressor is heavily coated with bullet lube, where it condenses due to the gas-cooling effect of the steel bars. The stuff is extremely tacky (sticky to the touch) and smells just like the lube does before firing. I believe the condensation begins away from the muzzle itself (less than two inches) because (a) it takes that long for the cooling effect to occur, and (b) the sheer velocity of the gases tends to push the by-products past and away from the muzzle. The deposits are very black, due to the combustion products mixed with the lube.
Note that the elongated bars used in many military flash suppressors were designed to reduce gas temperatures outside the muzzle by absorbing heat from powder gases, and in that way reduce the muzzle flash. Seems like they work the same with vaporized bullet lube, too. Most flash suppressors I've seen become less and less effective as the barrel heats in rapid fire. This is logical, because as the suppressor gets hotter it has less ability to cool the escaping gas.
I really noticed the formation of the lube deposits this morning, when I was firing into strong morning light and the front half of the FS was very dark with fouling while the rest of the device was relatively shiny. About 400 rounds had been fired without cleaning, at that point.
In my extensive cast-boolit shooting in the .308/7.62 NATO M1A, I discovered that the extended flash suppressor is giving me some indications about what might be happening to bullet lube once the bullet starts down the bore from the chamber.
We are all quite familiar with the "smokiness" of our cast loads, compared to the "normal" jacketed-bullet ammunition that sane people use. Based on the evidence derived from the flash suppressor, it's plain to see that a goodly proportion of the lube (Felix lube, in this case) is actually departing the muzzle as a vapor, not as a solid lubricant attached to the bullet.
I hasten to add that the lube is doing its job very well, because the rifle simply does NOT display bore leading with any load to date.
The forward half of the OUTSIDE of the suppressor is heavily coated with bullet lube, where it condenses due to the gas-cooling effect of the steel bars. The stuff is extremely tacky (sticky to the touch) and smells just like the lube does before firing. I believe the condensation begins away from the muzzle itself (less than two inches) because (a) it takes that long for the cooling effect to occur, and (b) the sheer velocity of the gases tends to push the by-products past and away from the muzzle. The deposits are very black, due to the combustion products mixed with the lube.
Note that the elongated bars used in many military flash suppressors were designed to reduce gas temperatures outside the muzzle by absorbing heat from powder gases, and in that way reduce the muzzle flash. Seems like they work the same with vaporized bullet lube, too. Most flash suppressors I've seen become less and less effective as the barrel heats in rapid fire. This is logical, because as the suppressor gets hotter it has less ability to cool the escaping gas.
I really noticed the formation of the lube deposits this morning, when I was firing into strong morning light and the front half of the FS was very dark with fouling while the rest of the device was relatively shiny. About 400 rounds had been fired without cleaning, at that point.