Various resources discuss selecting the proper alloy for your bullets based on the chamber pressure that your load will develop. Cast bullet reference on lead alloy's, min / max pressure, lube, shrinkage,
There's one in case you are wondering. The relevant info is 1/3 of the way down. Based on that information for the range of chamber pressures for Lyman #2 with a BHN of 15 would be between 21,330 and 35,000.
Let's say you loaded it to 17,000. How much would that affect accuracy?
While personally NOT a caster, here is what I have heard over the years, so take it for what it is worth...
The BHN is more important for speed than pressure. Reason being is pressure and heat go hand in hand. Heat tends to erode the bullets more than pressure by it's self. If you push the bullet to fast(no gas check) then you tend to erode the base, and leave parts in the bore. This leaves the bullet out of ballance, and accuracy goes out the window.
The harder the bullet, the less "sticky" it is in the bore; less fouling.
I'm a firm believer in the theory that "If it bleeds, I can kill it"
I suppose this isn't a very interesting topic. Thanks for the reply Darkker.
Does anyone know if this is covered in the Lyman Cast Bullet Handbook that I've been meaning to get?
The Eradicator – that chart/formula is used to get you close to the point, where a bullet of certain hardness will “obturate” in the bore.
A bullet too hard will not bump-up or obturate, with the results of leading the bore.
A bullet too soft will sometimes turn to mush/gel if the pressure is high enough and really lead the bore.
Will a 15 BHN Lyman #2 bullet shoot good at 17,000 psi… There are too many variables to say, like what loob is used, condition of your bore… I would just try it and see.
Cast bullets that are too "hard", can lead more than bullets cast too "soft". Most common sense cast bullet shooting, can be done with 20# wheel weights, and a 1# roll of solder. This alloy works well with moderate velocity, common sense loadings.
This alloy "upsets" well, and reliably fills the grooves in the rifling. If desiring a higher velocity, one can "quench" this alloy, and add a gas check. The real trick, is to determine the "right" fitment of projectile to barrel. And choose a powder that does not damage a non gas checked bullet.
The fellows on the Cast Bullet forum, have quite a bit to say about all this. Hope this helps.
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