Why softer bullets for light smokeless and black powder rifle and pistol loads? That's a good question and it's a concept that many shooters have trouble "wrapping the old brain around”. Many of us have long believed the conventional wisdom that a hard cast bullet is superior to softer ones with regards to performance. At higher velocities (especially in a gas checked design) this is true. However, for lighter smokeless or Black powder equivalent loads, softer alloyed bullets such as our "Cowboy Cast" line are best.

 I will explain to you why.

Lead bullets produce leading in a rifle or pistol when there is not enough pressure generated by the load to make the bullet obturate or “bump up” fully in the bore for the ENTIRE trip from case mouth to muzzle. When released from the mouth of a fired cartridge, a bullet must obturate acting as a tight fitting "gas piston" as the powder gases drive it down the barrel. Any gaps around the circumference of the bullets' base will allow those hot powder gases to flame cut and erode the lead at the higher powder burning temperatures. Even at lower power flame temps, this gas leakage around the bullet produces tipping or "skidding" effect down the barrel's bore, particularly ahead of the forcing cone in revolvers.

In a revolver these problems are worse due to the fact that the bullet must jump from the chamber throat in the cylinder (many of them grossly oversized to the bore diameter) and then slam into the barrel's forcing cone and be swaged BACK down to bore dimensions! Many times this dimensional change may total 0.10 of an inch!  Here again, a bullet which is soft enough to fully fill the cylinder throat properly prevents powder gasses from getting around the base of the bullet. The result is the bullet meets the forcing cone more squarely and in turn, exits the muzzle more consistently shot after shot.

Even rifle's can benefit from softer cast bullets. Traditonal Black powder cartridge shooters have long known that softer bullets are much more forgiving of generous differences in the chamber throat and groove diameters of many modern and antique BPCR rifles. Top level Schuetzen riflemen have for years proven the softer bullet alloys are the best way to shoot those matching winning, Sub MOA groups on those 200yard paper bulls eyes.

The ammo companies also have long known this. At the turn of the century the HARDEST bullet alloy one was apt to find in factory loaded cartridges was 1-16 tin/lead which is a BHN of only 12 at the most. MUCH softer than most commonly available "hard cast bullets" which start at BHN 18 (and go UP from there!) As a matter of fact most repeater cartridge loadings 44-40, 45LC etc. utilized a 1-60 alloy and were often times hollow skirted as well. This was a combination used to insure a complete gas seal and assured accuracy.

The noted handgun authority Elmer Keith long ago devised a clever formula, which is useful to this day in selecting the proper lead bullet hardness for proper obturation in most guns. It goes as follows:

Pressure of the selected load (in CUP's) -:-   1,422 = the HARDEST alloy (in BHN) that should be selected for proper bullet obturation. That is your bullet alloy should be equal to or less than that number.

Let's run an example of this say for a .357 mag revolver. Our selected load of powder develops 17,500 CUPs according to the powder manual. We plug that figure into our formula as such:

17,500-:-  1,422= 12.3 BHN

That means the bullets we should use for best accuracy, our bullets should be no harder than BHN 12.3 or less for best accuracy.

While Mr. Keith's formula is not an exact measure of the proper alloy needed, it has proven over nearly 75 years use by knowledgeable hand gunners to be VERY close to ideal.

What about an alloy that is too soft? Really, it is nearly impossible to use a lead alloy that is too soft unless a plain based bullet is pushed to velocities higher than 1,300 FPS OR a powder is selected that is VERY hot burning and produces a very high pressure to velocity ratio. Their are many, many moderate burning powders on the market today that are ideal for use with light smokeless cowboy action and BP equivalent loads. 

Classic bullets "Cowboy Cast" line at 11-12 Maximum BHN is ideal for these types of loads.

                                                                                                    By: James Linthicum