boolit alloy
So we have questions, what alloy will work in my gun, for my target, with the terminal effect I want?
Lots of 'info' on forums. High Sb will shatter, hard will lead, soft will lead, etc. What is correct?
So we try lots of 'stuff' to see what works. How do we find an alloy that meets the requirements?
BHN testers measure static stress/strain (force/distortion) Not a direct 'performance' indicator.
Data gleaned from several sources show deformation increases with impact ~50% (over static) with an additional 50% due to temp (0F to 160F). Navy studies show Pb has ~ 1000 psi plastic point - due to impact (from 22ft/sec). Static is about 2K psi.
1800 fps 165gr (0.24#) boolit stops in 0.008 sec (one foot of target). Not realistic, just an assumption as example.
As E=1/2m(v)^2, how does acceleration/deceleration affect alloy. A= d(v)/d(t). = d^2(x)/d(t^2) =F/m
Deceleration = 1800/0.008= -225000 = A = F/m = F/0.24#. So F=225000*0.24 = 54000# or (assume 40cal) 54000/.125=432000 psi. That is peak impact psi.
Deforming the boolit releases energy as does deforming the target. E=0.24/2*1800^2 = 388800. Assume 1/2 in boolit, the rest in target. 63000 calories. So the 165gr goes to 1k F on impact. This answer is NOT true as I just used simple algebra calc. True answer may be 10x lower but this gives an idea of the forces involved. Similar to firing so keeping the pressure down helps.
So we add stuff. Alloy additives Sn/Sb/Cu/As/Zn/S and some others.
I suppose the early guys used whatever would melt and cast. Later we got Pb/Sn, Pb/Sb/Sn of varying amounts. #2, 20:1, 40:1, etc. Generally known 'properties' of the additives; Sb - harder, Sn - better casting, Cu - malleability/hardness, As - faster hardening, Zn - harder, S - harder. So how much of these do we add. What effect does quenching have?
So --- Pb and metals are crystals. Imagine a 2-D grid of dots. You can place another dot on an empty space or substitute a Pb dot with something else. A limit is reached (saturation) when all the substitute/placement dots allowed are filled. If you add more, you get blobs of the replacing stuff. Like the Sb or Sn rich sides of the eutectic curve of #2. IIRC, As = 0.15, Cu = 0.3, Zn,Sb,Sn = 1.5, S = 1 (%wt). But the saturation % is temp. dependent. So the melt can be supersaturated. When we W.D. (quench fast) they are frozen in place. Supersaturated at room temp. When we air cool, we get normal saturation and blobs of the added stuff. We often hear of 'grain-refiners' such as As. Basically doing the same to the other stuff as they do in Pb. Makes the blobs smaller/stronger. These 'additives' also create larger molecules that fit in the dot-matrix and add to the 'hardness'.
So what does this mean?
My general 'rule' - for AC, use no more than room temp. saturation values - except for Sb. It seems to form molecules with almost all the others. I have used Sb/Cu to get BHN up in the high 30s but rock hard is not really needed (unless you want AP boolits). I don't normally see a need or use for Sn. I have been getting good accuracy results with 3-4% (wt) Sb in rifles, more for full fps 308. I am working to find a 'soft' alloy for low fps rifle and pistol. Additives of Zn/Cu/Sb alloy, all at very low %.
I will make one emphatic statement. Leading is not caused by soft or hard alloy per se. Lube failure, gas cutting and land stripping only.
No intention of stepping on LASC articles, we do have more industrial data available now. I don't agree with all their statements. I get tired of the old wives tales about alloys. No expert but been doing a lot of reading in the last couple years. Anyone that has more data, be glad to add. We don't have the Gov. developing this stuff for us.
Waco - doesn't answer your question, just gives an idea what can do what.