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Old August 4th, 2013, 12:58 PM #1
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Twist, Barrel Length, Bullet Weight

I know. Another one. It's either all the variables involved or my thick head because this isn't sinking in very well. There's a lot of good info in the threads linked further below. Thanks to all for the good reading.

So, I found this calculator (yeah, probably a dupe), but it seems to conflict with the chart Crab Bait posted. Of course, that chart doesn't appear to factor in bullet length and I'm not sure what barrel length is assumed.

http://bulletin.accurateshooter.com/...ty-calculator/

I used this picture for bullet lengths. Not sure how accurate it is.
http://www.bevfitchett.us/rifle-mark...allistics.html

Does the calculator seem accurate to you? Is there such a thing as too high SG?


OTHER THREADS
http://www.mdshooters.com/showthread...ighlight=twist

Quote:
Originally Posted by lx1x View Post
http://www.6mmbr.com/223rem.html

twist rates.. midway down.

http://www.mdshooters.com/showthread...ighlight=twist

Quote:
Originally Posted by Crab Bait View Post
This is just info from the net, but I thought enough of it to save it... others may shoot it down.


http://www.mdshooters.com/showthread...ighlight=twist
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Old August 4th, 2013, 01:02 PM #2
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That pretty much nails it for .556/223 AR barrels. Anything else will be entirely different.
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Old August 4th, 2013, 01:19 PM #3
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Here are the inputs I used on the calculator.

Caliber .224 inches
Bullet Weight 55 Grains
Bullet Length .76 inches
Barrel Twist 7 Inches/Turn
Muzzle Velocity 3100fps
Temperature 70 F.
Altitude 100 Feet

It shows SG = 3.75, which is well into the "Comfortable Stability" range that starts at 1.5. The chart posted above indicates that 55gr in a 1:7 is not the best or not as good as it could be. I just don't know what to make of that.
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Old August 4th, 2013, 01:30 PM #4
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From some very veteran loaders I've met they said bullet length has a ton to do with stability and spin rate which the graph you have doesnr account for. For a quick and dirty reference chart I think it works well but there will always be exceptions to this.
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Old August 4th, 2013, 09:18 PM #5
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Bullet length is the actual parameter that sets the required twist along with muzzle velocity.

Bullet weight is only indicative, in that heavier bullets in a given caliber are typically longer.
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Old August 29th, 2013, 11:54 AM #6
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will the barrel has what the twist is stamped into it? i mean i remember what mine is from the description when i bought if but some may not remember.
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Old August 29th, 2013, 12:19 PM #7
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Quote:
Originally Posted by rockstarr View Post
will the barrel has what the twist is stamped into it? i mean i remember what mine is from the description when i bought if but some may not remember.
Generally, yes.

Although I have seen (rarely) barrels w/out info stamped.
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