Scota@4570
54 Cal.
- Joined
- Nov 25, 2019
- Messages
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Mad Monk (Bill Knight) is the foremost expert on the subject of ML propellants. On the American Long Rifle Forum he posted:
"I just dropped in to see what has been going on.
To answer your question.
Pyrodex uses 17 parts of Potassium Perchlorate as part of the oxidizer system. Powder combustion converts that potassium perchlorate into potassium chloride. Minute crystals scattered over the surfaces of the bore. Given the right range of relative humidity each of the tiny crystals becomes an electrolytic corrosion cell on the surface of the metal. This "micro-pitting" happens very quickly. It makes the bore's surfaces look dull. Under magnification they are seen to be little pits in the metal. Most shooters who used, or use, Pyrodex find it necessary to frequently check the bore during storage. Once you get surface pitting of the metal it is difficult to insure no traces of the chloride have entered the porous metal in the pits.
This chloride pit corrosion was one of the driving forces behind the development of the 777 powder. It is free of any chlorides and will not pit corrode the bore. When the in-line crowd went to plastic sabot carrying pistol bullets the minute crystals of chloride left by Pyrodex made reloading without cleaning difficult at best. So getting rid of the potassium perchlorate became a must in the 777 development project. While the 777 is a bit more difficult to ignite, compared to Pyrode, it is a far better powder. More powerful and very clean burning. Being more powerful you can use less of it in a load. It's post combustion residue, as with black powder, may cause light surface rusting it will not pit corrode the bore.
Bill K."
"I just dropped in to see what has been going on.
To answer your question.
Pyrodex uses 17 parts of Potassium Perchlorate as part of the oxidizer system. Powder combustion converts that potassium perchlorate into potassium chloride. Minute crystals scattered over the surfaces of the bore. Given the right range of relative humidity each of the tiny crystals becomes an electrolytic corrosion cell on the surface of the metal. This "micro-pitting" happens very quickly. It makes the bore's surfaces look dull. Under magnification they are seen to be little pits in the metal. Most shooters who used, or use, Pyrodex find it necessary to frequently check the bore during storage. Once you get surface pitting of the metal it is difficult to insure no traces of the chloride have entered the porous metal in the pits.
This chloride pit corrosion was one of the driving forces behind the development of the 777 powder. It is free of any chlorides and will not pit corrode the bore. When the in-line crowd went to plastic sabot carrying pistol bullets the minute crystals of chloride left by Pyrodex made reloading without cleaning difficult at best. So getting rid of the potassium perchlorate became a must in the 777 development project. While the 777 is a bit more difficult to ignite, compared to Pyrode, it is a far better powder. More powerful and very clean burning. Being more powerful you can use less of it in a load. It's post combustion residue, as with black powder, may cause light surface rusting it will not pit corrode the bore.
Bill K."