Article #10: Buffers, Fillers, and other "taboo" subjects


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The Basement Articles #10: Buffers, fillers, and other taboo subjects

Three things we need to talk about here: FILLERS, BUFFERS, and WADS.

These all have their place when assembling cast bullet loads, although I generally try to avoid them for most work as all of them are more or less "bandages" for other problems. For some ends,though, the proper application of these things is a practical way to achieve them. I'll attempt to explain.

Fillers and buffers are two different things to me, although some use the term interchangeably. The reason I differentiate is that I frequently use buffers as a tool to achieve some particular, and potentially dangerous ends that many people don't fool with. The term "wad" is perpetually misused, oftentimes probably where "wadding" would have been more descriptive, but who knows.

Fillers are, to me, the fluffy ones like Dacron, Kapok, dryer lint, wool, cotton, Styrofoam packing peanuts, florist's foam, "fake" snow, cat hair, etc. Fillers don't raise pressure much, although they do promote efficient combustion by fooling the powder into thinking it is in a smaller cartridge case than it actually is during initial combustion, and also by locating the powder positively against the primer where it can get maximum exposure to the primer's heat. I like to call fillers "powder locators" because essentially that's what I use them for. The filler easily compresses forward as the primer blast goes off and early burn pressure begins, so the case volume is rapidly and gently expanded to "normal" and the powder continues to burn almost as if the filler weren't there.

Intermediate sorts of fillers are things like Puff-Lon (or however it's spelled), spherical HDPE pellets like some of the shotshell buffers, and other things that don't compress into a solid plug under pressure. These "flowing" fillers have more mass than the fibrous fillers, take up A LOT more volume under pressure, and loads must be reduced considerably when using them, but they don't tend to seal gas from the bullet base. Basically, they're true fillers because they effectively reduce case volume even at peak pressure.

Buffers are something I learned about from two guys on the Castboolits forum who rarely post anymore, so I'm preserving the technique, and my experiences of it's use here for posterity. I don't know if it was all their idea, but it certainly wasn't mine, although once the seed was planted I more or less learned how to use it on my own. Buffers are things that compact into a solid plug under pressure, increase loading density, tend to clump rather than flow, and can effectively relay the kinetic energy of the burning powder gas to the bullet without the gas actually touching it. They must fill the case and achieve slight compression to locate the powder, prevent mixing, and to work as a "buffer" between bullet and hot burning gas. This last is why we use the term "buffer" rather than filler, even though it serves the other purposes automatically.

My comments here on buffers and how I use them are made with the assumption that you realize that you can very easily kill or maim yourself or others using them if you don't know exactly what you're doing, so don't take this information lightly. Neither the site owners nor I will assume any responsibility whatsoever for anyone who chooses to use this information.


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Principally, I only use one thing for buffer as a matter of safety: BPI Original granular shotshell buffer used in ball, slug, and buckshot loads to help support the soft lead projectiles under acceleration and keep them from deforming. There are other things to use, but I won't go into them here except Cream O' Wheat, and only to add another disclaimer. COW is hygroscopic absorbs atmospheric or other moisture), and tends to form a starchy, solid mass when allowed to sit in a loaded cartridge case for any length of time, and this can cause a serious obstruction when fired since it won't compress and squeeze through a bottlenecked rifle case as easily as it does when it's dry, flexible, and fluffy. It typically absorbs moisture from the smokeless powder (or even gunpowder) itself when put in a cartridge case, and that increases the effective burn rate of the powder drastically, so it's a sort of "one, two punch" on raising the hell out of pressure in a stored load that's otherwise perfectly safe when fired the same day it's put together. Back to the BPI Original (not to be confused with the spherical version that is a true filler as I described earlier). In some instances, particularly high-powered rifles in which I'm attempting to achieve very high velocity and maintain accuracy, I use this PSB (polyethylene shotshell buffer) to fill the space between the powder and bullet base, with slight compression....

...What happens then is the buffer works against the restriction formed by the shoulder of the case to add more resistance to the powder pressure. More resistance=higher temperatures which=higher efficiency which=more consistent shot-to-shot burn which=smaller groups. This is a trick to get slow powders that we like for gentle launches of our delicate bullets to burn well, yet still not build too much pressure too soon. There is a delicate balance here since too much of a good thing raises pressure too much before the bullet moves and defeats the purpose of using slow, hard to light powder. The buffer extrudes into the neck and pushes the bullet into the throat without it being touched by the gas, so the neck expands behind the bullet as it moves forward rather than blowing past the base of the bullet and expanding the neck before the bullet moves as often happens with a high pressure load without buffer but with a well-fitting nose that obturates the throat. All that adds to accuracy. Oh, and the buffer plug follows the bullet all the way out the muzzle, shielding the bullet base from the yawing effects of muzzle blast at crown exit.

How much powder, what kind of powder, which cases to use it in, how much buffer, and particularly how much static compression to use is a little bit beyond what I'm trying to cover here in this post, and gets into the Twilight Zone of Ph, D. handloading, so I'd rather address it on a very specific and individual basis rather than attempt to establish general guidelines for its use. Sorry for the letdown, but feel free to ask specific questions if you're serious about applying buffer to a load and I'll share what I know.


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Now don't go to sleep, because THIS IS IMPORTANT!: Fiber fillers and wads must be used correctly or at the least you can "ring" your chambers. You've probably heard the term "chamber ringing" associated with the use of "fillers", along with the palpably nervous hush and furtive glances among those that consider putting anything inside a case other than powder and air is foolish and will always ruin your gun. While I certainly respect those who never step outside of well-established, published loading practices, there are some of us who, like Doral, "Imagine getting more" from our cast bullet loads and have learned how to safely and properly use fillers and wads to help us out occasionally. Chambers are ringed by one thing, and that's the IMPROPER use of fillers and wads. The sudden, high pressure, radial pressure wave deflected off of the bullet's base because the reloader didn't follow directions and tamped the filler/wad down on top of the powder and left an air gap between it and the bullet base is what caused the problem, not any mystical, inherent danger of a few tufts of fibers or a little disc of cardstock. When you compress the powder into a column and leave a big gap in between it and the bullet, the bullet becomes a bore obstruction. The powder lights and burns ferociously because it's crammed against the primer, then it pushes the wad forward (be it card, fiber, or a tamped tuft of Dacron or similar) like a piston that slams suddenly into the boolit base with tremendous force like a freight train hitting a concrete wall. Usually it doesn't blow the chamber before the bullet moves, but that force is directed outward as it concentrates behind the mass of the bullet, often stressing the chamber steel enough to form a permanent ring right behind where the bullet base is parked.

The proper way to use a fiber filler is to fluff, or "loft" it up when installing it in the case such that it occupies all of the space between bullet and powder. I don't mean pack it in there tightly, but let it have a little compression beyond what the fibers naturally have if you wad them in your hand and allow them to relax to their natural volume. I like Dacron for some loads because it has a very consistent, robust, natural springy loft to it and I can poke a tuft of it down into a bottlenecked case with a pocket screwdriver or blunted nail, leave a little bit up in the neck, seat a bullet, and know it's properly compressed and not going to ring my chamber. Lint, cotton, and wool don't have as much spring, tend to start wildfires, and can get sort of packed down like an old pillow through handling or recoil in a magazine, thus potentially becoming a wad against the powder and leaving the air gap we want to avoid.

The proper way to use a fiber or card wad, (true WADS in my mind at least, and notwithstanding the muzzle-loading, gunpowder guys) is right under the bullet, or in shotgun shells. Notice how shotgun shells are ALWAYS supposed to be loaded to 100% density? Heavy payloads, fast powders, and thin chambers are a recipe for rings if ever there was one, but how many have ever seen a ringed shotgun chamber from a properly assembled shotshell? Some of them are using a half-inch of wadding or more, but it's done so the powder column can't get a head start before it slams into the payload. Engineered crush zones have largely replaced separate overpowder wads in commercial offerings, but again, they cushion and build gradual resistance until the payload moves. I only use card wads in one instance, and that's in a high-pressure, paper-patched load involving a cartridge case that simply runs out of room for any other kind of buffer, but needs one to help protect the bullet base. I get a significant reduction in group size with my .45 Colt carbine launching a 340-grain, soft lead paper-patched slug out of an 18" barrel at over 1300 fps when adding a hard wad cut from soda can 12-pack cartons. The load is compressed already, nothing but as much Reloader 7 as I can pack in there.

Ok, in review, I only recommend Dacron fiberfill for powder location beween boolit and powder column and only in slight compression; I only use granular, PSB as a compacting buffer, and only then in specialized, high velocity applications; don't leave air gaps between your wads and the boolit base, and thanks for reading this!