Originally Posted by
jaybez101099
After reading more than my share of posts on here the twist rate factor still has me puzzled. Is the 1/30 one rotation every 30"s?
And if so does that mean a 24" barrel the sabot only is performing 3/4 rotation? If you are planning on shooting only a sabot-ed bullet is a slow or fast rate better? I noticed the whites are faster than most with a 1/24. Does a twist rate have a matching load preference as in 1/26=120g. I googled it and never found a direct answer other than PRB's were mostly 1/60ish but that didn't help me.
The length of the barrel really dose not have a lot to do with the twist. The length of the bullet and the velocity have to match up with in reasonable limits so the the bullet is stabilized like a spinning top. That is what keeps it form going end over end. That is why a smooth bore has trouble getting any accuracy at a distance.
Greenhil formula
Twist = 150 X D2/L
Where:
D = bullet diameter in inches
L= bullet length in inches
150 = a constant
This applies to muzzle loaders and if you were to us it for a cartridge gun that had a velocity of over 2800 FPS then the constant would be 180.
Think of it this way if your muzzle loader had a standard twist of 1 in 28 that is one complete spin every 28 inches if it had a velocity of 2000 FPS the the bullet is spinning 4286 times a minute. If you check with the green hill formula this will stabilize a bullet from about .75 to about .95 in a 45 caliber.
Hope this helps. Lee