220 Swift & 90gr Bergers...

[ISS]

I want to build a live varmint rifle in 220 Swift using a bolt action. I ended up somehow with about 300 of the Berger 90gr VLDs.
My Rockchuck hunts are at 3500ft or a bit higher.
We have much greater choices these days, any thoughts about a 7 vs 8 inch twist?

thanks,

Rich

 

[ELR LVR]

I know my 220 Sw Ack handles the Berger 85.5 with great accuracy in an 8 twist
I would find the OAL of the Bullet and get on Bergers site to use their bullet stability calculator
anything above a 1.4 and you will be fine
my SG Factor is approx 1.42 - 1.46 and you can see my 600 yd accuracy in the pics
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With something as fast as a Swift, I would be reluctant going anything faster than an 8 twist
due to risk of bullet failure
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It's a big catch 22
We want to drive the heavies fast
but by driving the heavies fast, we risk blowing them up in a fast twist also
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I just looked - Berger List their 90 VLD with an OAL of 1.254 ; BC of .534
Now I was going to say, with the BC and accuracy I get from an 85.5 Berger
I have seen no need to try anything heavier
And if we compare the length of the 90VLD 1.254" to the 85.5 of 1.167"
We can see that the 90 VLD is QUITE a bit longer
for not much more BC
90 VLD BC .534
85.5 BC .524
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With the length of the 90 VLD, I'd be more willing to bet it actually needs the recommended 1:7 twist
which, might mean you would have to load down your swift in order to use them so they don't come apart due to the RPM's a Swift will generate in a 7 twist barrel.
I would honestly sell them off and buy the 85.5 instead
I know for a fact the 85.5 can handle Swift Velocities in an 8 twist
since it handles my Swift Ackley Velocities just fine.
Most of the guys using the 90's and 95 SMK's are doing so with 223's and 22 BR's in 7 twists
but only driving them up to maybe 3200 fps, which is SLOW compared to a Swift cartridge
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IE: I don't see anybody else driving these heavy .224 Cal bullets to Swift Cartridge Velocities
of over 3500 fps
and using 7 twist barrels
and living to brag about it

 

[cb186]

I assume this is going to be a long range(600-1000yard) varmit gun?
I think I'd go 7ish twist, because I doubt your going to get to 3400, and an 8 twist would be marginal even at that speed.
I'd also make sure I'd get a .219" bore barrel.

 

[ELR LVR]

I assume this is going to be a long range(600-1000yard) varmit gun?
I think I'd go 7ish twist, because I doubt your going to get to 3400, and an 8 twist would be marginal even at that speed.
I'd also make sure I'd get a .219" bore barrel.

Im getting 3650 with 85.5's
I dont think 3400 with a standard Swift is out of the realm
Of course as I mentioned a person could load down until it works if bullet failures are a result
of using a 7 Twist
but that would negate the very purpose of using a Swift
a Guy may as well use a 22 BR by then if it came down to that
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It may work in a 7.5 twist
I know my recommended twist is 7.7, but------------
I'm fine with approx 1 inch groups at 600 and using an 8 tw.
I have enough Berger bullet failures in 6mm 8 twist going 3400 fps
I could not imagine what would happen if I went tighter and the limited bullet selection I would be down to
I use to use a 9 twist in 6mm, just so bullets would stay together
there is a ragged edge of going tighter twist and having bullets survive,
finding it usually means adjusting velocity
and it sucks being forced to load down just because bullets won't reach the target
when a cartridge is capable of so much more
-----------
It's like having a Pumped 327, and having to retard the timing so much just to survive on todays gas lol

 

[Charlie-NY]

I'd get an 8 twist and trade away the 90VLDs which aren't needed for your intended use. 7 twist barrels are blowing up a lot of good bullets.