OK, so let me get this straight. If I have a 58 cal with a 1x66" twist compared to a 1x48", the 48" twist will stabilize a longer bullet, whereas a 66" twist will stabilize a shorter bullet. True?

You are correct. The longer the bullet the faster the twist needs to be. Ron

Yes .... and .... no. Catch 22 here because it all depends upon the design of the bullet. I assume you're talking mini's, with their hollow base weight forward design, you can in effect have a mini that is considered far too long for a given twist yet it will work just fine. Reason being is that the overall length of the bullet is less important than the length of the major mass section.

In other words, you can't use the Greenhill formula to calculate twist rate for a hollow base bullet. Because the mini style is so more like a shotgun slug, it is entirely possible to have a twist that is too fast and thus will limit your velocity so as not to exceed the maximum RPM's the bullet will handle.

OK, so let me get this straight. If I have a 58 cal with a 1x66" twist compared to a 1x48", the 48" twist will stabilize a longer bullet, whereas a 66" twist will stabilize a shorter bullet. True?

I have a 1in66" .58 too. Shoots PRB's good but if you raise the powder volume with that twist it can end up pitching curveballs.

For round ball shooting 1in66" seems ideal for .50 cal, 1in72" for .54... you can see the progression happening.

My best friend's excellent Pacific Zephyr 12 bore (.72 cal.) is twisted at 1in144" to enable the highest possible powder charges with patched round balls.

Hammerspur,

The .58 ought to run fairly well with the 1:66 unless you're trying to push magnum loads. How much powder are you to it before it starts throwing curveballs?

Some of the best all-purpose twists for PRB's are:
.45 - 1:56
.50 - 1:60
.54 - 1:66
.58 to .62 - 1:72<SCRIPT type=text/javascript> vbmenu_register("postmenu_322587", true); </SCRIPT>