Twist Rate

emmab

emmab

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Hello I was wondering if somebody could explain, or point me to a page, that would explain the rate of twist in an AR .223 barrel. I can see a situation changeing with length of barrel and weight of bullet but there seems to be quite a few different twist rates available. Also, what would the best shooter be?(longer bbl? heavier round?)
Any info would be appreciated. Thanks. Pete
 
Normally the place to go to is www.ammo-oracle.com but it's down right now. An archived site is http://web.archive.org/web/20041015001332/www.ammo-oracle.com/body.htm or http://www.thepurplebuffalo.net/mirror/www.ammo-oracle.com/

username: ammo
password: ammo

A heavier round with a faster twist rate will generally provide stability at longer ranges with a .223 bullet. A longer barrel will give extra velocity, but the stiff shorter barrel will also have it's own advantages in not flexing as much. Generally a 1/9 twist out of a 16"+ barrel will launch pretty much everything beyond the ability of the shooter.
 
Thanks Mike. Sorry I didn't see the reply sooner. Great info on the ammo oracle. Couldn't get in the other site tpb . Now what is the concensus on ammo? >.223 or 5.56? Availability and price are always a concern. Now I'm starting to look for an upper and I really am just starting to figure it out. It's quite a broad topic with countless (or so it seems) possibilities.Thanks for the info. Pete
 
emmab said:
Thanks Mike. Sorry I didn't see the reply sooner. Great info on the ammo oracle. Couldn't get in the other site tpb . Now what is the concensus on ammo? >.223 or 5.56? Availability and price are always a concern. Now I'm starting to look for an upper and I really am just starting to figure it out. It's quite a broad topic with countless (or so it seems) possibilities.Thanks for the info. Pete
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If you can get 5.56 in Canada, let us know. :) Until then you're stuck with .223, because USA won't export any 5.56.

As for the upper, buy a NATO or a Wylde chamber, so you can shoot both 223 and 5.56 (if we ever see it again).
 
going back to the original question; the greenhill formula allows you to calculate the longest bullet that you can stabilize with a given twist rate. 150 x diameter squared and divided by twist gives the length of bullet. Normally you use 1" faster twist that the formula suggests. Also note that you can switch twist and length to calculate minimum twist from bullet length.

cheers mooncoon
 
quote kirill "If you can get 5.56 in Canada, let us know. Until then you're stuck with .223, because USA won't export any 5.56."

Well that narrows it down a bit! Good advice on the chamber selection too. And thanks mooncoon I'll try and give the formula a whirl once I get some more data.

Any comments on barrel length or personal likes or dislikes over one type or sort? Thanks again
 
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emmab said:
quote kirill "If you can get 5.56 in Canada, let us know. Until then you're stuck with .223, because USA won't export any 5.56."

Well that narrows it down a bit! Good advice on the chamber selection too. And thanks mooncoon I'll try and give the formula a whirl once I get some more data.

Any comments on barrel length or personal likes or dislikes over one type or sort? Thanks again
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What do you want this AR for? A precision bench gun should have a long stainless heavy barrel. An off-hand IDPA shooter sould have a lightweight chromed 11.5". Now, a brand new rifle will be hard to get with a barrel under 16" (again, USA export restrictions), so for general purpose, I recommend a lightweight 16". I have a HBAR 16" and I am now trying to balance it since it's front-heavy.
 
emmab said:
quote kirill "If you can get 5.56 in Canada, let us know. Until then you're stuck with .223, because USA won't export any 5.56."

Well that narrows it down a bit! Good advice on the chamber selection too.
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If you are just using it for recreational shooting, to get a little lead down range, then you might want to stick with a 5.56 chamber. It will shoot both rounds safely but a .223 will only shoot .223 safely. This is my understanding from ammo oracle.
ammo oracle said:
Opinion: In general it is a bad idea to attempt to fire 5.56 rounds (e.g., M193, M855) in .223 chambers, particularly with older rifles.

Fact: SAAMI specifically warns against the use of 5.56mm ammo in .223 chambers. The .223 SAAMI specification was originally made with bolt rifles in mind.
http://www.ammo-oracle.com/body.htm#diff
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I think the accuracy will be the same for fun purposes but may not be so for benchrest shooting. Not sure there though as I next to nothing x 10 about BR with an AR.

Manditory disclaimer - Match your ammo to the barrel. ;)
 
Nats said:
If you are just using it for recreational shooting, to get a little lead down range, then you might want to stick with a 5.56 chamber. It will shoot both rounds safely but a .223 will only shoot .223 safely. This is my understanding from ammo oracle.
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That's what I said in my post, you didn't notice it :)

I wonder how accurately the Wylde chamber shoots, and how well it accepts sloppy ammo like Wolf.
 
kirill said:
I wonder how accurately the Wylde chamber shoots, and how well it accepts sloppy ammo like Wolf.
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On the first part, very. I've done just over a quarter inch with one (in a semi). On the second part, while I'd not put Wolf in my gun, it feeds SA surplus just fine.
 
emmab said:
quote kirill "If you can get 5.56 in Canada, let us know. Until then you're stuck with .223, because USA won't export any 5.56."

Well that narrows it down a bit! Good advice on the chamber selection too. And thanks mooncoon I'll try and give the formula a whirl once I get some more data.

Any comments on barrel length or personal likes or dislikes over one type or sort? Thanks again
Click to expand...


LONG BABY 20" and no less........you want all the guys at the range saying YEA that 20" sure does the job :p :p :p :D

I personaly dislike any thing under 20" They just look so tactical - I like the long gun look and probably performs better ( long gun wise ) pretty much all I will use it for!

I got my eyes on a scope that costs 2X as much as my whole AR project :confused: :D :D
 
kirill said:
That's what I said in my post, you didn't notice it :)

I wonder how accurately the Wylde chamber shoots, and how well it accepts sloppy ammo like Wolf.
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:redface: No.

Been checking into the Wylde chambering too. Seems to be the halfway point between 223 and 5.56 so I still wouldn't be using 5.56 in 223. Who knows though, it might be the perfect fix.
As AR owners are always in agreement, I'm sure the question will be put to rest soon
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What's the trade-off in balance vs accuracy with a heavy barrel in a shorter rifle? For IPSC/IDPA matches, for a 16" barrel, is it better to have a lighter profiled barrel for balance, or a heavier barrel for more accuracy?
 
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