Originally Posted by
Larry Gibson
I am just absolutely amazed by what some of you write. I’m reading that from most of you that it is, in fact, “easier” to load for accuracy with slower twist barrels. This is even at moderate velocities of 1800 -2000 fps and the higher velocities up through 2400+ fps. It is “easier’ to get best accuracy at 1800-1900 fps from a 10” twist than a 7.5” twist. The 7.5” twist gives best accuracy down in the 1400-1500 fps range. It is “easier” to get the same accuracy at 200 fps with a 12’ twist that you get at 1900 fps with the 10” twist. With 14’ twist it is just as “easy” to get the same accuracy at 2400-2500 fps that you get at 2200 fps with a 12” twist and at 1900 fps with a 10” twist and at 1500 fps with a 7.5” twist. If we do the simple math we find the RPM at each of these “easiest” velocities is pretty much the same. Then the same who say "it's easier with slower twists" then want to say RPM has nothing to do with it. Talk about contradictions.
Now before starmetal, 45 2.1 and others go off again note I am referring to normal cast bullet loads with regular type cast bullets for rifles. If any of them would bother to look at a listing of past and current rifle cast bullets they will notice that the long nose bore riders are the “norm”. Also note that I have said “normal cast bullet loading techniques”. This obviously excludes the specialized methods I and others use who have the inclination and equipment to use them. Most cast bullet shooters have neither the inclination to use those advanced techniques or they really don’t care for HV cast bullet loads. Most all regular cast bullet shooters also lack the extensive equipment that I , starmetal, 45 2.1 and others have. And they are not inclined to purchase that equipment/tools.
The obvious conclusion for the majority of cast bullet shooters is that RPM is the key component to accuracy here. To get best accuracy, given normal and adequate cast bullet loading techniques, simply keep the RPM below a certain level. We can do this two ways; controlling the velocity in a barrel with which we have or by using a barrel with a slower twist if higher velocity is desired or required. Go above that RPM level and almost every cast bullet shooter loses accuracy with such loads. That is a threshold. It can be pushed higher by a few of us with the equipment/tools and inclination to do so. A couple also have some “magical” and “dangerous” methods they use to push the RPM threshold higher. However, the majority of cast bullet shooters will continue to find, with regular cast bullet loads, the RPM threshold to be real and above which accuracy will deteriorate.
The majority of cast bullet shooters are either already aware of this, even though they may not understand it. The others should be made aware of it as it will help them better enjoy our sport and avoid needless frustration. If any of them desire to accumulate the required equipment/tools and want to learn how to push the RPM threshold for accuracy at HV then that information should be readily available without all this “I’m the master and you’re the student or it’s “dangerous” so I won’t tell you ridiculousness.
RPM is indeed the factor a cast bullet shooter must over come if accuracy at HV with a given twist (generally 10” of faster) is desired. The facts are plain to see.
Larry Gibson