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velocity in relation to barrle twist

 
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Old 02-03-2004, 01:47 PM
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velocity in relation to barrle twist

Dosen't velocity determine twist rate needed to stablize said bullet.

EG: 223 with 1-12 twist 55gr bullet 3200 fps
223 with 1-12 twist will not stablize 70gr bullet(no clue as to how fast it would go)
22-243 with 1-12 twist 55gr bullet 4100 fps

22-243 with 1-12 will stablize 70 gr bullet at 3800.(maybe not to the point of .5moa acuracy)
This is a poor eg. but i hope ya get the idea.
Is'nt it RPM's that stablize the bullet.If so less twist at higher velocity is needed to stablize the same bullet.

Is'nt this true?????
[ 02-03-2004: Message edited by: Crazycooydog ]

[ 02-03-2004: Message edited by: Crazycooydog ]
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  #2  
Old 02-03-2004, 04:19 PM
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Re: velocity in relation to barrle twist

Twist rate has FAR more influence on bullet rotation rate than velocity does.
Most barrel manufacturers only make recommendations for twist based on the bullet weight/length and disregard potential velocity.

Many 22 centerfire rfles have a 14" twist regardless of whether it is a 221 or 220Swift.
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Old 02-03-2004, 06:20 PM
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Re: velocity in relation to barrle twist

Varmint hunter
Isn't gyroscopic stability proportional to RPMs?
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Old 02-03-2004, 06:38 PM
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Re: velocity in relation to barrle twist

Heavier/longer bullets do, indeed, require a higher rotational spin on the bullet to maintain stability.
My point is that a velocity change +/- has a much smaller influence on the rate of that spin than does a minor change in twist rate.
I shoot a 22-243AI and 80gr VLD bullets. This rifle needs an 8" twist to stabilize these heavy/long bullets just the same as a .223 would. Even though the 22-243AI can shoot them at 3,600+ ft/sec, which is MUCH faster than a .223, I still need the same 8" twist. Would the extra velocity allow me to use a 10" or 12" twist barrel - No. I could probably get by with a SLIGHTLY slower twist but this would be insignificant.

VH
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Old 02-03-2004, 07:34 PM
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Re: velocity in relation to barrle twist

Yes I understand that certain twist's are needed for certain bullets. I just was wondering how a 223 shooting a 70gr bullet at a MUCH slower velocity, than say a 22-243 with the same bullet at a MUCH higher velocity would use the same twist barrle.

I'm talking a velocity difference of like 6-800 fps. It's got to make a difference.

Just thinking of my factory rem 22-250 1-14 shoots 50gr v-max's awsome,it all so shoots 55gr very good.
1-14 twist is recamended for 50-52gr bullets...right?(Lilja's recamendations)
1-12 for 55-60gr bullets
1-9or10 for 68-69gr bullets

Varmint Hunter
For sure in a higher velocity 1-9 twist. ???Couldn't ya?????
I am just trying to understand this whole concept. Looks like it's the rpm's that are what stablize the bullets.Larger bullets need more rpms to get them to stablize.
There fore is there such thing as over stablizing a bullet.I think yes because it comes apart if it spins too many rpm's.. ????Does'nt it????

[ 02-03-2004: Message edited by: Crazycooydog ]

[ 02-03-2004: Message edited by: Crazycooydog ]
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Old 02-03-2004, 08:14 PM
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Re: velocity in relation to barrle twist

Try not to take what I have stated out of context - A change in velocity does change the rotational speed of the bullet but just not enough to reqire a different twist rate. At least not in a reasonable comparison.

Yes, if you take it to the extreme, like shooting the same bullet in a 218 Bee and a 220 Swift you MAY be able to use different twists. However, they would likely both work quite well with the same twist.

To answer your other question: An 80gr VLD will not stabilize in a 10" twist, not even in the 22-243AI. The 9" twist is something that I'd have to try, but I doubt it.
Now how about a 8.5"? [img]images/icons/wink.gif[/img]

Here is something else to think about: When shooting over looong range there is not only velocity loss but rotational spin decay. Do you need to increase the rotational spin at the onset in an effort to compensate for the inevitable decay? [img]images/icons/confused.gif[/img]

VH
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  #7  
Old 02-03-2004, 08:22 PM
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Re: velocity in relation to barrle twist

I realy know nothing about this whole twist thing.

Here is the delema:
I am building a 22-243
I would like to shoot 55gr gamekings FOR SURE
May like to try 68's for wind but realy don't want to take anything away from the 55's.

[img]images/icons/confused.gif[/img] What to do [img]images/icons/confused.gif[/img]
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