.223 twist rates

Heym SR20

Well-Known Member
Don’t forget that the .222 gained its reputation shooting 50, 55 and 60gn bullets with a 1 in 14” twist.

There are good reasons for a fast twist barrel if you want to shoot long heavy for calibre bullets out the 223, especially if you have a short barrel and need the faster twist to stabilise long bullets to make up for lack of velocity thanks to the short barrel.

In the UK we can only use 223 on vermin and Roe in Scotland and Muntjac and Chinese Water Deer in England and a 50 to 55gn bullet is more than enough. It’s flat shooting out to 200m so you don’t have to worry about drops etc.

The long 70gn 223 bullets are what you would use to shoot bigger deer such as Whitetail in the US, and many thousands each year using this cartridge.

But in the UK it is illegal to shoot bigger deer with a 22 Centrefire. For bigger deer In England you need a minimum calibre of .240, and Scotland a 100gn bullet and there are min muzzle energy requirements as well.

So unless you want to shoot long heavy for calibre 223 bullets out of a 223 at targets over say 300 metres you don’t really need a .223 with a fast twist barrel.

I would focus instead on finding a rifle that you like in your budget etc and go from there.
 

Miki

Well-Known Member
Well put Mr @Heym SR20

Reading through this thread it seems that most are not understanding that the 'length' of the bullet is the critical factor.
The heavier the bullet, in a .223 chambering. the longer the bullet is.
The less dense the material its made from the longer it will be by comparison (a brass 55gr bullet is longer than a lead 55gr bullet).
The shorter the riflleings twist the faster the spin. A 1:14 will impart a rotation on a bullet of 155,000rpm wheras a 1:10 will spin to 216,000rpm

(MV x 720)/Twist = rpm
(3000fps x 720) = 2,160,000 / 12 (1:12 twst) = 180,000rpm

Don Millar came up with a rule that defined the stability of a bullet relative to its spin rate and length.
Bryan Litz and Mike Courtney modified the Miller rule to accomodate plastic tipped bullets which has proven to be accurate.

There are a number of online calculators available. This one works well https://bergerbullets.com/twist-rate-calculator/

What the math shows is that when you exceed a certain length (or weight if you insist) the bullet becomes unstable, instability = innacuracy.
 
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