7.5 twist verses 8 twist in 6.5 cm
- Thread starter dzander
- Start date
Never actually switched but my first 65CM I used a 7.5 twist Bartlien barrel.
I can't honestly tell if there is any disadvantage but have mostly just run the 147eldm.
Other than two boxes of factory ammo ( Winchester 140 match and Norma 130 match) I have shot nothing but 147eldm and Sierra 150smk reloads.
If you have any intentions of running the heavy for caliber bullets I don't think there's a downside and shouldn't be hindered by running bullets in the 130 grain range.
I went a little faster twist because I didn't want a barrel over 23" finished length.
I can't honestly tell if there is any disadvantage but have mostly just run the 147eldm.
Other than two boxes of factory ammo ( Winchester 140 match and Norma 130 match) I have shot nothing but 147eldm and Sierra 150smk reloads.
If you have any intentions of running the heavy for caliber bullets I don't think there's a downside and shouldn't be hindered by running bullets in the 130 grain range.
I went a little faster twist because I didn't want a barrel over 23" finished length.
Reason I asked i was on the Berger sight , under resources they have a program where you can plug in your bullet, velocity, twist rate of your barrel and shows how well the combination you use stabilizes the bullet. as you change from 1:8 to 1:7.5 it shows a higher rate of stabilization. It was mentioned on the last Sniper hide podcast with the Berger guys.
If you were running on the ragged edge of stability I could see there being a difference.
But like has allready been said the 147eldm does just fine in a 1-8 twist and there is lots of data confirming that.
I just went a little faster to guarantee excellent stability if I was running slower than what most do since I didn't want a 26" + barrel length and was being maybe a bit overly cautious.
The 23" barrel I'm running easily gets the 147 and 150smk into the 2700fps range so it's not a velocity issue but I know I am running them with excellent stability numbers based on the calculators.
Would another 100fps from 4" more barrel be better, I don't really care since I never really chase velocity.
But I don't think it's a useless gain if you need it.
But like has allready been said the 147eldm does just fine in a 1-8 twist and there is lots of data confirming that.
I just went a little faster to guarantee excellent stability if I was running slower than what most do since I didn't want a 26" + barrel length and was being maybe a bit overly cautious.
The 23" barrel I'm running easily gets the 147 and 150smk into the 2700fps range so it's not a velocity issue but I know I am running them with excellent stability numbers based on the calculators.
Would another 100fps from 4" more barrel be better, I don't really care since I never really chase velocity.
But I don't think it's a useless gain if you need it.
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