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twist rates
Posted: Sun Jan 20, 2013 11:43 am
by westernsky
g'day all,
ive just been on the sierra website looking for 30 cal projys, and it seems that the side note they had on the 210gr and 240gr matchkings about minimum twist rates is gone. does anyone know if this is because they have been revised and they have realised these bullets no longer require the faster rates to be stable?
i have a 1 in 12 twist and would love to use the higher bc 240gr or at least the 210gr
happy shooting
Posted: Sun Jan 20, 2013 11:52 am
by westernsky
forget that, must have been a glitch in my internet, when i retried it showed up!
on another note however, have they put a limit on the twist rate due to the expected mv being very low out of say, a 308win or similar, whereas if the mv was much higher, in the region of 2800 to 3000 fps would the increased rpm be enough to stabilise the heavier and longer bullets?
any thoughts would be much appreciated
happy shooting
Posted: Mon Jan 21, 2013 6:57 am
by bsouthernau
Hornady claim that their 225gr BTHP Match will stabilise in a 1:12
Barry
Posted: Mon Jan 21, 2013 8:39 am
by Brad Y
Surely that must be a typo, or at least it would stabilise in a 338 lapua necked down to 30 cal.
From reading alot of the FTR stuff overseas, 1:12 you can use up to about a 175gr-185gr pill
Posted: Mon Jan 21, 2013 2:34 pm
by bsouthernau
Brad Y wrote:Surely that must be a typo, or at least it would stabilise in a 338 lapua necked down to 30 cal.
From reading alot of the FTR stuff overseas, 1:12 you can use up to about a 175gr-185gr pill
It surprised me too Brad. I wrote to them and asked as I feared my 1:10s that I shoot the 208A-Max and 210 Sierra MK in mightn't be fast enough. The 225 is longer than both of those but that was their reply. Haven't found time to do any exerimenting myself.
Barry
Posted: Fri Jan 25, 2013 11:54 am
by westernsky
just ordered the 225's so i will keep you guys posted on how they go. hopefully hornady are right!
Posted: Fri Jan 25, 2013 12:07 pm
by Brad Y
Im trying the 168 amax in a 12 twist remington factory barrel on sunday. If they keyhole (which im not expecting) then I would say your ones wouldnt be any good.
Posted: Fri Jan 25, 2013 12:43 pm
by westernsky
guess i will have to see as theyve been ordered. 168's for me would be way too light, mv would be somewhere near 3500 im guessing.
i was going to run the 200gn sierras but the heavier the better for my cartridge.
Posted: Fri Jan 25, 2013 1:06 pm
by Brad Y
Apparently Wurgabup are going to run FO for thier prize shoot- are you going to come down and have a go?
Posted: Sat Jan 26, 2013 9:57 am
by westernsky
when and where? if i have my load sorted ill be there for sure