.220 Swift/90gr

[Boisblancboy]

Ok guys I'm looking for some reloading data for the .220 Swift and the 90gr VLD's. I've been looking around all over the net and can't seem to find anything. Any links or data would be appreciated.

 

[Bart B.]

Here's Sierra Bullets' data for 80 grain bullets in the 220. I'd cut the charges about 1 grain for 90's.

 

[Boisblancboy]

Thanks Bart. I've been doing a bunch of reading and have found tons of articles from a few years ago or more about the 90gr bullets coming apart.

I'm hoping the 1-7 or 1-6.5 twist, which is recommended wouldn't cause this at around 3000 FPS, unless the bullet technology has gotten better over the years.

 

[284winner]

Thanks Bart. I've been doing a bunch of reading and have found tons of articles from a few years ago or more about the 90gr bullets coming apart.

I'm hoping the 1-7 or 1-6.5 twist, which is recommended wouldn't cause this at around 3000 FPS, unless the bullet technology has gotten better over the years.

I think that fast of a twist IS what's actually causing the bullet separation. Traveling at more rpm than the bullet can handle. IMO a slower twist would do better. 7.5-8.0 may be best. At the speeds a swift produces should make up for the slower twist. Stabilization should be just into the stabilized range. It's kind of a fine line with those heavies. No issues in a 223 but going into the speedsters, it becomes another thing. I'm going to try out 90s in my 22-250 AI. It's an 8 twist barrel. I built it for 80 eld-m bullets but will give the 90s a go.

 

[Ned Ludd]

It's been a while since I looked, but you can find some information regarding the use of the 90s in high velocity .22 cal cartridges if you look long enough. Here are a couple examples:

http://forum.accurateshooter.com/threads/long-range-22-cal-suggestions.3788825/

http://forum.accurateshooter.com/threads/new-22br-and-90vlds.3812610/

Not sure how much .220 Swift info you will find, but the issue of jacket failure has definitely been addressed. One approach I recall reading about was to use a 7.2 twist barrel, rather than the 7.0 (or below) twist commonly used in .223s. I've played around with the numbers using Berger's twist rate calculator and with the kind of velocity you should be able to get from a .220 Swift, the 90 VLD should still retain an Sg of greater than 1.5 (full BC) in a 7.2 twist barrel. Presumably, the slower twist would be slightly less hard on the jacket. You can use Berger's calculator to determine the values for yourself, but I recall that going much slower than a 7.2 twist began to cut into the Sg enough to lower the effective BC of the bullet. You can get away with that to some extent, but slowing the twist rate too much will cause you to effectively lose enough BC so as to defeat the purpose of using the 90 VLD in the first place.

 

[IdahoSharpshooter]

Berger Manual has a full page of powders and velocity.

 

[seymour fish]

It's been a while since I looked, but you can find some information regarding the use of the 90s in high velocity .22 cal cartridges if you look long enough. Here are a couple examples:

http://forum.accurateshooter.com/threads/long-range-22-cal-suggestions.3788825/

http://forum.accurateshooter.com/threads/new-22br-and-90vlds.3812610/

Not sure how much .220 Swift info you will find, but the issue of jacket failure has definitely been addressed. One approach I recall reading about was to use a 7.2 twist barrel, rather than the 7.0 (or below) twist commonly used in .223s. I've played around with the numbers using Berger's twist rate calculator and with the kind of velocity you should be able to get from a .220 Swift, the 90 VLD should still retain an Sg of greater than 1.5 (full BC) in a 7.2 twist barrel. Presumably, the slower twist would be slightly less hard on the jacket. You can use Berger's calculator to determine the values for yourself, but I recall that going much slower than a 7.2 twist began to cut into the Sg enough to lower the effective BC of the bullet. You can get away with that to some extent, but slowing the twist rate too much will cause you to effectively lose enough BC so as to defeat the purpose of using the 90 VLD in the first place.

Personages of note have used a Broughton 5c as a work-around to prevent jacket failure

 

[Bart B.]

I'm hoping the 1-7 or 1-6.5 twist, which is recommended wouldn't cause this at around 3000 FPS, unless the bullet technology has gotten better over the years.

22 caliber 90 grain bullets need to be spun at least 270,000 rpm for best stability and accuracy. What ever muzzle velocity and rifling twist makes that happen is good.

3000 fps X 720 velocity-twist conversion factor / 8" twist equals 270,000 rpm.

Use a 1:8" twist.

 

[Ned Ludd]

22 caliber 90 grain bullets need to be spun at least 270,000 rpm for best stability and accuracy. What ever muzzle velocity and rifling twist makes that happen is good.

3000 fps X 720 velocity-twist conversion factor / 8" twist equals 270,000 rpm.

Use a 1:8" twist.

Sorry...an 8-twist isn't nearly fast enough. Even setting the temp and elevation at 65 degrees and 500 ft, respectively, Berger's twist rate calculator indicates you'd be giving up somewhere in excess of 10% of the theoretical maximum BC of the 90 VLD. Might as well just switch to an 80 gr .224 bullet at that point.

 

[Bart B.]

Sierra's 22 caliber 90 grain bullet is only 1.17" long, not 1.25". JBM stability software puts it in the green with a 1.3 stab. factor. Perfect for temperatures above 50 degrees F. It's BC is .500 plus 1%, not .256.

http://www.shootforum.com/forum/bulletdb.html

 

[Ned Ludd]

Those are G7 BCs, not G1. For the SMK 90, Berger's calculator estimates you'd be giving up 5% of the theoretical maximum BC (1.171" OAL, 3000 fps, 65 degrees F, 500 ft elevation). That's still enough loss to put it closer in performance to an 80 gr .224 bullet. There is no good reason to go with a twist rate slow enough to do that.

 

[Bart B.]

Sierra says their .224" 90 grain bullet has a .563 to .480 G1 BC.

One good reason to shoot bullets just barely fast enough to stabilize them in any faster will cause the worst balanced ones to jump off the bore axis ad the leave. One of the benchrest things. In colder weather, they'll add a few tenths grains of powder to spin bullets faster in thicker air.