Accuracy and twist rate.

[mpett1]

Bullet weight and twist rate and accuracy. What is the rule of thumb

Lighter bullet weight = Higher twist rate and
Heavier bullet weight = Lower twist rate

Or is it the opposite.

[Tomcat088]

I'm not trying to flame you here, but you really need to do a search around the forum before you post up new topics. This question has been covered many times in a great amount of detail. If you search and can't find the threads, maybe we'll be happy to post some links up. It's just a waste of bandwidth and time for most of us have already taken the time to answer the question already. That's what forums are for, to store data to be looked at later, and ask new or modified questions. You would do well to search.

[RaisedByWolves]

Tom, stop wasting your own time with posts like that, someone else will come along tomorrow and do the same thing. Theres no stopping it. Besides, search sucks most times and I for one am here to connect with other people and have fun with this hobby and medium.


People who want to look up info know about the local library, google and such. People like this are looking to strike up a conversation.



So anyway, yeah, its the opposite.


Heavier bullet, faster twist.

Lighter bullet, slower twist.


AKAIK, velocity and bullet diameter/length Can play a part also, but Im unsure to what extent.




Bandwith.......Bah!

[mjfletcher]

This is gonna get into all kinds of physics.

For bullet weight, a heavier bullet will maintain its twist rate longer than a lighter bullet. For a visual demonstration, take a small plastic ball and an equal sized ball bearing and spen them both. The ball bearing, being heavier, will continue to spin long after the plastic ball stops. Newton, Object in motion, etc.

For how fast the bullet spins/twists as it travels, velocity will determine that. The faster it travels down the barrel the faster its rate of twist.
These speeds are waaaaaaaayyyyy slow but they'll serve to demonstrate.

ie: 18 inch barrel with 1 in 18 twist. If it takes a bullet
.5 seconds to travel down the barrel it will rotate 1 full turn before leaving the barrel and have a rate of twist of 1 turn every half second or 2 turns/sec.
.25 seconds to travel down the barrel it will rotate 1 full turn before leaving the barrel and have a rate of twist of 1 turn every quarter second or 4 turns/sec.
.125 seconds to travel down the barrel it will rotate 1 full turn before leaving the barrel and have a rate of twist of 1 turn every eighth second or 8 turns/sec.

The heavier bullet will maintain its RoT longer than a lighter bullet increasing its accurracy at greater distance when the initial RoT is the same.
Increasing the RoT of the lighter bullet will give it the same accuracy at the same distance as the slower moving heavier bullet.

[knight0334]

longer bullets, faster twist rate. shorter bullets, slower twist rate.

all copper slugs of the same weight as a lead or compound slug are longer and need faster rates, even though they are the same weight.

There is also the velocity factor too. The faster the bullet, the less twist rate you need.