Barrel twists

Mumptia

Mumptia

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There has been a fair bit of discussion on the board about bullet weight and rate of twist being a factor in accuracy.

What is the significance of the rate of twist in rifles?

When you buy new rifles you don't get a choice on rate of twist do you?:confused:
 
To slow a twist and the rear end (the heavy end) is going to want to overtake the front end. Gives stabilization. Not sure of the disadvantages of spinning too fast other than some light jacketed varmit bullets can't handle the force.

When choosing a rifle's twist (assuming you have a choice) you have to decide what the rifle is going to be used for. Long range targeting your probably going to want to use long high-BC bullets that take more to stabilize. A varmit rifle would be the otherside. Most rifle mfg's try to barrel their guns to suit as general a use as likely for the particular chambering.

Do a search on some of the barrel mfg's websites for charts on reccommended twist rates. Lilja has one.
 
Too drastic of a twist rate can over stress the jacket of a projectile, and in extreme cases actually cause the jacket to strip off once it exits the bore.
 
Mumptia said:
There has been a fair bit of discussion on the board about bullet weight and rate of twist being a factor in accuracy.

What is the significance of the rate of twist in rifles?

When you buy new rifles you don't get a choice on rate of twist do you?:confused:
Click to expand...

Different projectile weights need different twist rates to stabilize them and make them fly true. Heavier bullets need to be spun quicker to be stabilized.

Manufacturers choose a twist rate that works for a calibre, being able to stabilize a wide range of bullet weights. Occaisionally it won't be a fast enough twist for the heaviest of bullets. ie. you might need a non standard (faster) twist rate if you want to shoot 75 grain bullets out of a .223. The reverse could be true too.
 
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It's not so much heavy bullets, but longer bullets that require the faster twist bbls.

That's why heavy round nose bullets TEND to shoot better than spire points of the same weight in rifles with a slower twist.




sc
 
Ok, that makes sense

There was a thread a couple of days ago on match bullets and how they are designed for accuracy and cannot be counted on for consistant expansion. Therefore are not an ideal bullet for hunting.

Is the twist going to make a large significance if you shoot a match bullet and say an Interbond of the same weight in the same twist barrel?

How many different variations of barrel twist are there?

Sound like rookie questions, but in all my years of hunting I've never really given any thought to the rate of twist.
 
Thank you SuperCup and others for these very interesting info about barrel twist and bullet weight. The pac-nor site was very informative.

Snowhunter
 
There is a simple mathematical formula to determine whether a given weight/length/calibre bullet will be stable at a given velocity. I have a nice version in an XL spreadsheet if you are interested.
 
oldbadger said:
There is a simple mathematical formula to determine whether a given weight/length/calibre bullet will be stable at a given velocity. I have a nice version in an XL spreadsheet if you are interested.
Click to expand...


I'd like to see that. That would go just great with what I am doing in class now.

When you get a minute send it to

robertw@fvsd.ab.ca

Thanks
 
Mumptia said:
I'd like to see that. That would go just great with what I am doing in class now.

When you get a minute send it to

robertw@fvsd.ab.ca

Thanks
Click to expand...
Im sure if you google "Greenhill formula" you will find it.
Mooncoon also posted the formula in the BP section under
"did I screw up?" , a thread that was stsarted by bulletsmith
Cat
 
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