hey all, I wanted to try some 69 gr sierra match kings in my 220 swift. For the life of me, I cant find any data on line or in any of my books. Thought Id see what you guys thought.
Thanks.
Henry.
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hey all, I wanted to try some 69 gr sierra match kings in my 220 swift. For the life of me, I cant find any data on line or in any of my books. Thought Id see what you guys thought.
Thanks.
Henry.
That's because swift rifles are typically 14-twist. Even at an ambitious launch velocity, you will never get that long of a bullet stable.
http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi
The 69gr SMKs are very unique in there design, with there very short bearing surface, they are more forgiving and act more like
a 55gr than the 69gr that they are, 42-44 gr of H414, Win780, H380, or CFE223 will get you there.
Dean
awesome thanks guys! glad to hear a positive feedback on the 69smk...
Dean, if i used 43 gr of H380 and the 69 gr smk you think that would be a good place to start? I had thought about using 70 gr data and starting a few gr under but there is no H380 data for the 70 gr data.
Thanks again!
Henry.
Bearing surface, while helpful/hurtful of accuracy; has nothing to do with total length, NOR with the RPM required for stability.
Use the link I posted, look up the length, and fill in the blanks. You will see what does or does not have a prayer for stability with your conditions.
I shoot the 69 SMK in my 22-250AI that is a 1:8 twist. Capacity wise it is very similar to a Swift. IMR 4007SSC works well in my rifle. 3600 fps is easily obtainable in my 28" barrel. I personally don't think the 1:14 swift would have a chance to stabilize a 69 SMK, but heck try it and see what happens. I personal thought a Swift could only shot with a 52 gr bullet....��. Luck, Tim