There is almost zero information on the net. Does anyone have some good data for lighter bullets (1-16 twist)?
I tried 52 gr Nosler Custom Comp bullets over 38 grs of IMR 4895 that averaged 1/2" at 100 yards. It grouped half that just fire forming the brass.
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October 19, 2007, 11:51 AM
I seems to me 1/16 twist is excessively slow for a Swift, or a blown-out AI Swift with modern bullets. The original Swift loading used a 48 grain semi-pointed bullet in a 1/14 twist barrel.
Todays bullets are more aerodynamic and much longer for a given weight, especially ones like the Nosler CC BTHP.
You may need to go much lighter then 52 grain BTHP bullets to get best accuracy out of it.
I think Speers 45 grain spitzer is closer to the old Swift bullet length then about anything else currently available.
You are correct. My Swift has a 1-14" twist. From what I understand 1-16" was common for the .220 Ackley.
I fire formed the brass with factory 50 gr spitzers and the group sizes were around 1/4". Is there that much difference between the two bullets?
October 19, 2007, 10:25 PM
Hogdon suggests you add 5% to the parent cartridge data both the starting load and the max for AI cartridges. They don't give data for them because there are too many variables in the rifles according to their FAQ's.
October 20, 2007, 02:06 PM
Is there that much difference between the two bullets?
Yes, if the 50 grain was a flat base spitzer.
We already know the Nosler is a BTHP and is 2 grains heavier. The BT adds length over a flat base, and the HP adds length over a SP spitzer.
That is a world of length differance in a marginal twist barrel.