Comments on: How Ballistic Coefficent Varies with Twist Rate (Stabilization)

By: gus

gus — Mon, 30 Aug 2021 10:20:56 +0000

I can’t say it’s better, but the
450 BC should retain velocity better at the end of 500 yards, so if it can keep away from 1.0 then it should work. the .350 undoubtedly will so there’s no problem with that one. at that point it depends which one bucks the wind better.

By: Christopher van Wyk

Christopher van Wyk — Mon, 23 May 2016 11:24:38 +0000

Hey Brian. I am looking for a bullet for my .243 with 1:10 twist for paper punching up to 500m my problem is that the 0.450+ bc bullets are long and my SG comes down to 1.2 and less. Is it better to use a bullet with a 0.350 bc a.d 1.52 sg or a 0.450 bc with a 1.2 sg

By: Bryan Litz

Bryan Litz — Mon, 09 Mar 2015 12:07:36 +0000

It’s hard to say that any bullet has a ‘max RPM’. Bullet failures are mostly caused by excessive pressure and velocity. Long rough barrels are a big contributor. Twist rate (RPM) is actually a small contributor to bullet failure.
The perception that fast twist rate is related to failure may be due to the fact that long bearing surface bullets are more susceptible to failure (when pushed really hard) and they require a faster twist to stabilize. In other words, it’s not the faster twist that causes the failure.
-Bryan

By: Bobr

Bobr — Fri, 06 Mar 2015 22:14:00 +0000

Bryan,
Is there any data as to max RPM on the Berger 140 VLD 6.5 target bullet

By: Guy

Guy — Fri, 06 Mar 2015 17:19:50 +0000

Back when my eyes were a lot better then they are today I shot service rifle AR .223 at 1000 yards. I had a Kriger 7 twist that was good enough to wine the state championship over the bolt guns. Ever since then I could never get another barrel to perform like that at 1000. Thinking back they were 8 twist. I think the seven twist made the difference in this case.

By: Bryan Litz

Bryan Litz — Fri, 06 Mar 2015 13:34:37 +0000

Bobr,
Not really. Some people worry about ‘overstabilization’, but that’s not really a thing. Like you said, the only real risk is if you’re on the verge of blowing bullets up, a dramatic increase in RPM may put you over the edge.
-Bryan

By: Bobr

Bobr — Fri, 06 Mar 2015 00:04:56 +0000

Bryan,
Is there a point where the SG can be too high and cause issue’s from being over stabilized, other than coming apart during flight

By: Bryan Litz

Bryan Litz — Thu, 05 Mar 2015 21:29:44 +0000

Not wrong,
But not as good as it could be. I always thought that if you had good groups, you had to have enough stability to be maxing out the full BC. This turns out not to be the case.
Personal example; I shot 185 Juggernauts out of my 1:13″ twist Palma rifle for a whole year. They shot awesome. I won the Midwest Palma and other matches with them; super accurate. Turns out my stability factor with this twist was so low that BC was being substantially compromised. It’s difficult to observe this with a Palma rifle and iron sights, especially since I didn’t know to look for it.
Now my Palma rifles are 1:12″ or 1:11″.
You won’t see an improvement in short range groups by improving your SG a little, but the BC will be improved if you’re bringing SG above 1.5.

-Bryan

By: Mike

Mike — Thu, 05 Mar 2015 20:35:14 +0000

A 7mm 180gr Hybrid leaving a 1:9 twist barrel at around 2850-2900fps seems fairly common in F-Class.

Where I’m at (43′ ASL), stability is only marginal at most temperatutes (1.4x according to the calculator).

Even at someplace like Ben Avery, where the elevation is around 1,100′ ASL), the stability is not much better (but at least it’s over 1.5).

Are we all doing something wrong?