Bloke on the Range RECREATES HISTORY with John D. Pedersen’s Cartridge Wax Process

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:


When checking the Wikipedia safety sheet for a substance, this is not really what you want to see.


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!

Nathaniel F

Nathaniel is a history enthusiast and firearms hobbyist whose primary interest lies in military small arms technological developments beginning with the smokeless powder era. In addition to contributing to The Firearm Blog, he runs 196,800 Revolutions Per Minute, a blog devoted to modern small arms design and theory. He is also the author of the original web serial Heartblood, which is being updated and edited regularly. He can be reached via email at


  • Tony Williams

    “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.”

    I understand that the fluted chamber was first patented in Italy by Agnelli some time in WW1 and was used in the SIA retarded-blowback MG of 1918.

    • Yeah, but I guess that nobody outside of a small circle of Italians were aware of that at the time (Italian patent documents are even now difficult to get hold of).

      • ostiariusalpha

        A little bit after the Pedersen, but it seems like the Russians had been paying attention.

  • E.D. Sartin

    Wasn’t it one of the AA guns or tank guns that you greased the rounds prior to loading with something like axle grease?

  • Twilight sparkle

    Reminds me a lot of the coating on 5.7×28

  • Tassiebush

    Next step is to add this to .17wsm and roll out blowback carbines and rifles in it.

  • BrandonAKsALot

    Lacquer coating can serve this purpose as well. It’s a bonus benefit to increasing shelf life. FN coats the 5.7×28 to aid in extraction in the P(S)90.

  • Archie Montgomery

    One of the Italian made light machineguns of the pre and Second World War period employed an ‘oiler’ to facilitate extraction of fired cartridges. Blowing dust complicated the matter; the resultant mud in the action wasn’t much better than the stuck and torn off cases in the chamber.

    The ‘hard wax’ application is ingenious, I suppose. However, it is another ‘step’ in the manufacturing process, making the manufacture of said ammunition more time consuming and costly. Not to mention it is really a hurdle for those who reload.

    Too many firearms designs avoid the problem successfully for this – waxing or lubricating cases – to be of any but historic interest. Somewhat like the Gyro Jet arm system; it’s interesting, but fairly pointless.