A retarded blowback rifle extracts cases from the chamber while they are still under considerable pressure – over 35,000 PSI. Because of this pressure, the walls of the cartridge cases adhere strongly to the barrel’s chamber walls, while the head is forced back. Under normal circumstances, this would cause a catastrophic case head separation, therefore a successful retarded blowback weapon needs some kind of lubrication to free the case walls from the chamber and facilitate extraction at such high pressures.
Today, this is usually accomplished via integral cuts in the chamber called “flutes” that reach up to the case mouth, which allow gas to flow around the case and equalize the pressure between the inside and outside of the case walls. However, when John D. Pedersen set out to design his retarded blowback rifle in the early to mid 1920s, flutes had not yet been invented. Instead, he invented a hard wax process to coat each cartridge, creating a thin, almost invisible wax that not only was dry and didn’t attract dirt, but protected the cartridges from corrosion or season cracking!
Unfortunately, this process utilized carbon tetrachloride, a highly toxic substance:
Bloke on the Range, an avid patent hound, set out to recreate the Pedersen waxing process, but instead of using carbon tetrachloride, he used much safer dichloromethane. Watch the video below to see his process and his results!
Here at TFB, we got the once in a lifetime chance to shoot an original Pedersen, and its wax-coated ammunition! I certainly attribute the good condition of the 90-year-old .276 ammunition that we used to the wax-coating; Pedersen’s lubrication process really did work!