Quote:
Originally Posted by Por_sha911
Jeff-thanks!
It has been my understanding that shooting cast lead makes for a lot more cleaning. True or not?
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If you are shooting "store bought" bullets yes, that is absolutely true. We simply cannot buy decent cast bullets. There are a few reasons for that.
First and foremost, the alloys used in commercially cast bullets are universally far too hard. This is driven by the handling requirements of manufacturing, packaging, and shipping. They have to be hard enough to not get deformed through all of this, including just minor dents or nicks on their bases and driving bands. Any of that will hurt accuracy.
Cast bullets are absolutely dependent upon either swaging down when entering the bore, or obdurating ("bumping up") when they enter the bore. We generally try to use cast bullets that are at least .001" over groove diameter, .002" is even better if it will still chamber. Soft lead alloys are easily swaged down or bumped up when entering the bore, providing a gas seal that prevents leading. Hard bullets, while they will still swage down (they have to or they wouldn't go down the bore), will never "bump up". In either case, they will not seal as well as a softer bullet.
Leading occurs when there is gas leakage past the bullet. These hot, high pressure gasses essentially vaporize small bits of lead and deposit them in the bore ahead of the bullet. The passing bullet then irons them in, causing "leading". Leading isn't really caused by the sides of the bullet in contact with the bore "smearing" as much as it is by this blow-by.
Bullet lubricants are meant to mitigate this, since we will never get a perfect gas seal. Commercially applied lubricants have the same problem, for the same reasons, that the lead alloys have - they are far too hard. Too hard to get blown out of the lube groove by those hot gasses, too hard to get squeezed out of the lube groove under acceleration. They simply stay in the lube groove and do nothing. The soft lubes required to get satisfactory cast bullet performance would not survive packaging and shipping.
Bullet shapes are also dictated by manufacturing requirements. Good sharp, square edges on the base of the bullet are paramount in cast bullet shooting. They also help when applied to the driving bands and lube grooves. Well, these sharp edges make it more difficult to drop the bullets from the molds. Commercially cast bullets have beveled bases and rounded driving bands and lube grooves so that they drop easily from the molds. The beveled bases are the worst - they give that gas erosion a place to start, where a good sharp edge helps stop it.
Sometimes these bullets work well enough in lower pressure, "standard velocity" loads in calibers like .45 ACP, .38 and .44 Special, .45 Colt, and the like. Velocities below 900 fps or so, pressures in the under 20,000 PSI range. They will still lead a bit, but not nearly as bad as they will in magnum revolver loads or rifle loads.
With all of the cast bullets I shoot, I only have one gun that mildly leads its bore, and it only does so with really heavy hunting loads. Never with lighter plinking loads. I'll put up with that, because it is a hunting revolver, and I only shoot enough of the heavy loads to ensure it's still zeroed. Even my 1,900 fps "Marlin loads" in the .45-70 do not lead, and cleanup is as easy as with any jacketed bullet.
So, yeah, it's the nature of the cast bullets a lot of guys shoot. All of the commercial ones I have tried have leaded the bore. Not quite so bad at lower velocities, but completely unusable at higher velocities.