220 Swift
Anyone out there have a custom built 220 Swift with a 1-12 or 1-10 twist? I have a Ruger 77V (26") with a 1-14 twist that has an eroded barrel that I need to replace. My main bullets I shoot for prairie dogs are 50-55 grain. I have noticed several of the Sierra 50 grain bullets that key holed on me. Am I foolish to go with a 1-10 twist on a replacement barrel?
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I would look at either:
Pulling the barrel and cutting it and re-chamber or re barrel to a 1-12 twist.
I think 1-10 would be a little fast with bullets of that weight going full speed in the swift. You may run into yaw problems.
Here is the JBM stability rate calculator.
http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi0 -
The .220 Swift has gotten along with a 14 twist since 1935.
Your 50 grain bullets are keyholing because the barrel is worn out, not because you need a faster twist.
Ken Waters did a Pet Loads with a 10 twist .22-250. He wrote that it was most accurate with 60-70 grain bullets, that a standard 14 twist was better with 53 grain bullets.
On the other hand C.E. Harris wrote that a 9 twist .223 he had was more accurate with 52 grain benchrest bullets than 68 grain NM bullets.
Sounds like a crapshoot to me.0 -
My mongrel 220 Swift has a 1-14 twist and shoots best with 50 grain Ballistic Tips. It shoots cup and core 55 grainers OK-just not quite as good as 50's.
A word of caution: use extreme care if loading for a faster twist barrel vs. a slower twist. That can raise pressure.0 -
A friend has a 22/6mm that is very similar ballistics to the Swift. He has a 1/12" twist and he shoots everything from 50 gr to 64 with no problems. 0 -
Rebarreled a 22-250 with a 1 in 10 twist. Groups every thing from 50 to 70 grain sub MOA Have not tried 80 gr. 0
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