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#1961940 - 07/25/11 11:44 AM Rifling twist vs. Bullet weight
Catsniper97 Offline
Junior Member

Registered: 01/24/11
Posts: 41
Loc: NC
Title says it all how does rifling twist affect the correct bullet weight for a gun?

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#1961944 - 07/25/11 11:47 AM Re: Rifling twist vs. Bullet weight [Re: Catsniper97]
markley Offline
Die Hard Member II

Registered: 11/12/10
Posts: 1334
Loc: Iowa
The faster the twist the heavier the bullet it can stabilize. take a 1:12 twist for a 223. it should stabilize up to 55-60gr bullet. A 1:9 twist will stabilize a up to a 69-70gr bullet. if you were to shoot a 69gr bullet in a 1:12 it would not group very well.

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#1961996 - 07/25/11 01:17 PM Re: Rifling twist vs. Bullet weight [Re: markley]
skb2706 Offline
Die Hard Member with a vengeance

Registered: 10/31/03
Posts: 4686
Loc: Denver, Colorado
Technically the preferred twist rate is based on bullet length and not necessarily weight. In the case of lead free bullets this is significant.

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#1962009 - 07/25/11 01:39 PM Re: Rifling twist vs. Bullet weight [Re: skb2706]
Ducksoup Offline
Die Hard Member II

Registered: 11/20/03
Posts: 1379
Loc: Gig Harbor, Washington
Originally Posted By: skb2706
Technically the preferred twist rate is based on bullet length and not necessarily weight. In the case of lead free bullets this is significant.


What skb said.
check out this link. It should help answer your question. thumbup1
http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi
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#1962197 - 07/25/11 06:02 PM Re: Rifling twist vs. Bullet weight [Re: markley]
Shynloco Offline
Die Hard Member II

Registered: 08/30/09
Posts: 1394
Loc: Apple Valley, CA
Generally, I'll agree with what Markley writes. However, I have a Savage Model 12 VLP DBM that has a 1:9 Twist that has been verified by two gunsmiths. But, it won't shoot 69 gr or 70 gr bullet worth a darn in term of accuracy @100 yds. On the flip side, it loves 52 gr and 53 gr bullets and groups incredibly well. Bottom line is that the rule of thumb (barrel twist) doesn't always hold true for every rifles and barrel.

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#1962229 - 07/25/11 06:47 PM Re: Rifling twist vs. Bullet weight [Re: Shynloco]
2muchgun Offline
PM Junkie

Registered: 01/18/05
Posts: 14231
Loc: Michigun
Length is more the issue than weight. It just so happens that they kinda go hand in hand.

The reason why recommended twist rates do not always hold true(as Shynloco states) is that RPM is the actual determining factor of whether a bullet will stabilize or not. Twist rate just happens to be the simplest way the manufacturers can convey this information to the consumer, because most do not have a chronograph.

Recommended twist rates are "generalizations". In other words, they are what will work most of the time, in most rifles, chambered for a given caliber/cartridge, with a given bullet. At pressures which are known to be safe. They are not written in stone.

Higher velocity will often stabilize a bullet that is supposedly too long for a given twist rate. With higher velocity, however, comes higher pressures. Manufacturers do not want to go out on a limb and specify something that could possibly be unsafe in some rifles. Therefore, they stick to "generalizations" and what they know will be both safe, and workable.........

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#1962257 - 07/25/11 07:15 PM Re: Rifling twist vs. Bullet weight [Re: Catsniper97]
RONINFLAG Offline
Die Hard Member

Registered: 02/07/10
Posts: 940
Loc: AZ
if you go to 6mmbr.com and go to 6mmbr info- you will find that an 8 twist will shoot everything good to great from 55-107. there is some info on twist rates on riflemansjournal.com too. i think the quality of the barrel is very important.

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#1962259 - 07/25/11 07:18 PM Re: Rifling twist vs. Bullet weight [Re: RONINFLAG]
2muchgun Offline
PM Junkie

Registered: 01/18/05
Posts: 14231
Loc: Michigun
The quality of the barrel may affect accuracy and velocity, but RPM is still the determining factor of stabilization......
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#1962296 - 07/25/11 08:20 PM Re: Rifling twist vs. Bullet weight [Re: 2muchgun]
tnshootist Offline
Die Hard Member with a vengeance

Registered: 11/26/10
Posts: 4894
Loc: East Tn
That link to JBM is interesting to play around with.It says my 9 twist is yellow at 3300fps but green at 3400fps.However at 3300fps with dropping barometric pressure it will go green.I did not know pressure had anything to do with stabilization.
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#1962315 - 07/25/11 08:57 PM Re: Rifling twist vs. Bullet weight [Re: tnshootist]
2muchgun Offline
PM Junkie

Registered: 01/18/05
Posts: 14231
Loc: Michigun
Yellow at 3300 but green at 3400. Exactly like I said. Higher velocity will often stabilize it. It's just that higher velocity/pressure aren't always safe. Hence, the "generalizations".......
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#1962331 - 07/25/11 09:18 PM Re: Rifling twist vs. Bullet weight [Re: 2muchgun]
JDolezal Offline
Seasoned Member

Registered: 02/08/10
Posts: 222
Loc: Maybee, MI. U.S.
What happens when you try to shoot a bullet that you don't have the reccomended twist rate for. I pushed these harder in order to acheive more RPM's like 2much stated but couldn't quite get them stabalized.

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#1963593 - 07/27/11 10:53 AM Re: Rifling twist vs. Bullet weight [Re: JDolezal]
tnshootist Offline
Die Hard Member with a vengeance

Registered: 11/26/10
Posts: 4894
Loc: East Tn
I'm not sure how to get 3500 out of my .243 with the 105s.The load books I have max out before you get there.
Shooting in Rem 700 in good shape.Do any of you shooters have a recipe I could borrow that you have been using?
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#1966102 - 07/30/11 10:03 PM Re: Rifling twist vs. Bullet weight [Re: tnshootist]
UncleDoc Offline
Seasoned Member

Registered: 01/31/07
Posts: 468
Loc: North Carolina
Like 2muchgun said, length is more of a factor than weight. Of course weight effects velocity and velocity effects how many revolutions per minute you get as you move down the barrel and out the end. Ask any barrel maker and they will tell you that length is the biggest factor. If you look at the end of your bullet box from Hornady, Nosler, Sierra, et al, you will see the weight listed, not the length of the projectile. And you can believe that a 90g Sierra is not necessarily the same length as a 90g Hornady or Speer.

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