Lrsnsam Posted June 17, 2017 Posted June 17, 2017 Dumb question but I need to clear something up. How much dextrin should I out in my BP comps? I hear some people say add 1 percent and others say 5 plus. Also, when is not a good time to add dextrin?
lloyd Posted June 17, 2017 Posted June 17, 2017 Dex should likely be used at a minimum of 5% in most compositions. It adds a bit of smoke, but we use 6.25% (1oz/lb of composition, plus-weight) So, for five pounds of composition, you'd ADD 5 ounces of dex. There aren't too many compositions that are 'sensitive' to it, although it has some fuel value. For the most-part, compositions with Parlon (and some Sarans) can be bound with acetone-bearing solvent packages, and those with more than about 6-7% red gum may be bound with alcohol-bearing solutions. Lloyd
Jessehk Posted June 17, 2017 Posted June 17, 2017 I usually add 3% of the weight of KNO3+ charcoal + sulfur. Seems to work well for me
lloyd Posted June 17, 2017 Posted June 17, 2017 (edited) 3% is not enough to bind most compositions hard-enough to survive hard lift or break forces. You'd be better-off with 5-6.25%. That's just a 'professional' view... not binding. Lloyd Edited June 17, 2017 by lloyd
Mumbles Posted June 19, 2017 Posted June 19, 2017 Not all dextrin is created equally. Good quality, acid catalyzed, commercial dextrin will work better gram for gram than something lower quality (or homemade). For black powder specifically, it will also depend on how you're forming the granules. Screen granulated material will generally use more dextrin. I always use 5% (approximately) just out of habit and ease. I've tried 3 and 4% and didn't notice the grains being notably softer or more crushable using good dextrin. I also didn't notice it burn any faster as some have claimed. If you're pressing and granulating your BP you don't need as much dextrin, if any at all. The pressing and consolidation provides it's own hardness and durability to grains. I don't believe most commercial BP uses any, but may be mistaken. Someone who regularly uses this method could probably provide more details. The notable exception is when using black powder for making rockets. People have had issues with incomplete consolidation when using too much dextrin. The prevailing theory is that the grains are too hard to totally break down and consolidate into a solid mass. You'll want to use no dextrin or maybe 1%. This is less of an issue with pressing vs. ramming. As far as when, I don't think it really matters. I add it toward the end of milling personally. There are some people who say that using a dextrin solution, or dextrin liquor as it's sometimes more commonly referred to, provides a faster product but I haven't seen much conclusive proof of that. Try a couple of things and see what works for you. Even with using accepted best practices, you need to find what works best for you and your materials. Consistency is the most important thing.
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