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Scorpio64

Good Article on Twist Rate

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Below is an excerpt from a well written article on The Importance of Twist Rates.  It is relatively short, and explains, in mostly plain language, the effects of an incorrect twist rate.  One of my pet peeves is when some folks say "naw, ya can't over stabilize a boolit", well, yes you can.  Over stabilizing a bullet won't necessarily make it shoot poorly, you may get pretty decent groups.  But, they won't be the best groups that bullet or your rifle are capable of producing.

It's important that rifle shooters have a basic understanding of twist rates and how it affects what you feed your rifle. 

 

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For many years, rate of twist was a topic left to gunsmiths and benchrest competitors.  But with the increased popularity of the .223 Remington came factory loads with bullets weighing from 36 to 77 grains, and many shooters had no idea why their rifles shot so well with some loads and so poorly with others. Some figured it out pretty quickly. Eventually, faster twist rates like 1:9 became the norm for ARs, and even faster twist rates became more popular with shooters keen on shooting 75- to 77-grain projectiles from their .223s. Today, twist rate is a common topic of discussion at the shooting range. But twist rates played a major role in shaping the guns we shoot today long before they were a common topic of conversation. The 6mm Remington is one example that comes to mind.

 

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Over-stabilization as a result of a too-fast twist rate can occur, resulting in a bullet that travels along its downward arc with its tip pointing skyward, exacerbating wind drift and hastening velocity loss. Ideally, the tip of a properly stabilized bullet should tip downward as the bullet begins its downward arc. Clearly, an over-stabilized bullet is not conducive to accuracy, but it is only noticeable in extreme cases of over-stabilization and at very long range. You'd never notice it at hunting distances.

You can read the rest of the article here --->  https://www.shootingtimes.com/editorial/ammunition_st_twistrates_200809/100194

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Good read.

The ST article cites one of my favorite cartridges as an example, the 6MM Rem. But I procured my Rem. 700 1981 version with the 1:9 twist (really 1:9.25.) It can stabilize hunting bullets up to 105 grains, and target/varmint bullets down to 70 grs., the lightest I've tried. I learned early on back in the 80's that the old style Hornady 70 gr. HP when handloaded would disintegrate on me when pushed past 3,600fps.  And like every individual rifle and its respective barrel, it has its favorites and not so favorites when it comes to bullet weights and bullet style. 

Another good read on bullet twist: http://bulletin.accurateshooter.com/tag/twist-rate/

Be sure to download the Excel spread sheet from Don Miller (referenced in the above article) for calculating twist rate for a given bullet. 

 

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