New Sierra Matchking

[308BAR]

For the 30cal they will require/recommended faster then conventional 1:9t for the 200s and 1:8 for the 230s(conventional being 1:10). So the really BC will be less if using a 1:10 or slower twist. IMO requiring a faster twist rate is very limiting for most competitors and mostly eliminate all factory made rifles. Considering most of the bullet competitors only require a 1:10 to stabilize and optimize the bullets BC ie 200.20x. Sorry don't know which site the chart was pulled from.

 

[FatBoy]

I'm having hard time wrapping my head around a 7.5 twist 300wm or 300NM. I wonder if these can be pushed fast enough in tight twists to make the BC work? It would seem (I am just wondering out loud) that these may be at a point where you risk jacket damage to get the higher BCs...

I was hoping to try the 200gr 30s in my 300WMs, to try against the 230OTMS. I could push them much faster, with equal or less recoil and BC is about the same. No brainer, but my tubes are 10 twists, which may not work. After my failure with the old 175 7mm SMKs in a 9 twist (they called for 8) I'm gunshy.

Am I just stuck in 2005?

 

[Laurie]

After my failure with the old 175 7mm SMKs in a 9 twist (they called for 8) I'm gunshy. Am I just stuck in 2005?

Hell, lot's of us are stuck in 2005 - my wife says I'm stuck in 1975 ............ and she may well be right about that!

I am surprised though that you believe you had trouble with the superb old 175gn SMK in a 9 twist barrel. At 2,800 fps in standard ballistic conditions, the Sg value (coefficient of stability) is a healthy 1.64, almost identical to that of the longstanding 308 Palma combination of the original [#2155] 155gn MK and a 13-twist barrel. This was one of the longest lasting long-range competition partnerships of recent times. (It survives too on this side of the Atlantic as the UK NRA specified the bullet in its Lithuanian manufactured GGG match ammunition.)

I did some testing with the 175 in a 7mm-08 long-throated F-Class rifle with a 9-twist Bartlein and results were very good except that I would have had to use hot burning 'high-energy' powders to get sufficiently high MVs. There was nothing wrong with the groups though. That also applied to the 180gn SMK in that barrel, it too having a very close Sg value in the 1.6s.

 

[JBT47]

Hell, lot's of us are stuck in 2005 - my wife says I'm stuck in 1975 ............ and she may well be right about that!

I am surprised though that you believe you had trouble with the superb old 175gn SMK in a 9 twist barrel. At 2,800 fps in standard ballistic conditions, the Sg value (coefficient of stability) is a healthy 1.64, almost identical to that of the longstanding 308 Palma combination of the original [#2155] 155gn MK and a 13-twist barrel. This was one of the longest lasting long-range competition partnerships of recent times. (It survives too on this side of the Atlantic as the UK NRA specified the bullet in its Lithuanian manufactured GGG match ammunition.)

I did some testing with the 175 in a 7mm-08 long-throated F-Class rifle with a 9-twist Bartlein and results were very good except that I would have had to use hot burning 'high-energy' powders to get sufficiently high MVs. There was nothing wrong with the groups though. That also applied to the 180gn SMK in that barrel, it too having a very close Sg value in the 1.6s.

Agreed. I shot the barrel out in my 7 WSM with the 175 SMK’s in a 1-9” twist Krieger. I live in Mississippi at basically sea level as well.

 

[FatBoy]

maybe it was primers? I don't know. Rifle shot 1" 5 shot groups at 300 yards but I couldn't break a 197 at 1k. Mostly elevation shots, and I didn't have time to mess with it before a regional so I put a 6.5x284 barrel on and was back to 199s.

That said, Caliche Pit has that barrel now and it seems to hammer 180BH and 180 ELD-Ms,.but he is a known deplorable so....

I really hope I can spin the new 200gr 30 caps fast enough to get the BC close to .7 in a 1:10. I'd be a happy camper for sure.