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6.5 dia twist rate
hadjii
Member Posts: 976 ✭✭
I'm looking at a Lilja 6.5-06 barrel I seen here on gunbroker, but the twist is 1 in 8. My question is this. Is that too fast of a twist to stabilize the lighter bullets, such as the 120 grainers or perhaps maybe 100 grain bullets? Thanks in advance
Comments
No it isn't too fast. Unless you want to shoot a long ways with light bullets. Over rotating a bullet won't have extreme effects on a light bullets if they are very close to concentric. Meaning the center of gravity along the fore/aft center is within .0001" -.0002" of the center of mass. Some say it can still hold decent accuracy if the difference is as much as .001" If you rotate a bullet less it has less propensity to magnify this defect if there is one.
Edit:
For longer ranges the cg around the lateral axis will have more effect. In short, the bullet acts like a top. The rotation keeps it's nose pointed in the direction it came out of the barrel. As a lighter bullet extends out it wants to stay nose up. The wind hitting the increasing angle of the bottom side of the bullet makes it want to 'yaw' or wobble nose-up/nose down. With the nose-up/down motion the precession wants to act at a 90 deg. angle to the original force placed on it...making it yaw in circles.
So, for short range light bullets, no problem. Long range...could be a problem. That twist is perfect for really heavy bullets in that caliber.
The 1:8" twist is what's accepted as a 'standard' twist currently. It's fairly fast when compared to other twist rates for other calibers but these .264" bullets are also long for caliber and use the faster twist effectively. This twist will handle most of the Match weight (length) bullets as well as the shorter and lighter bullets. There are a couple of things to consider however:
The '06 case has a sizable powder capacity. When loaded with the shorter, lighter bullets, you are loosing efficiency or wasting powder without gaining any significant velocity. This case really shines when loaded with the heavier bullets.
The barrel you're considering appears to be 21" long. Matched to the cartridge it's chambered for, I'm not surprised that the owner decided against it. The muzzle blast and inefficiency will be much higher than with a 24-26" barrel which would be my suggestion for this cartridge. This is compounding the inefficiency of using the lighter bullets with the 6.5-06 cartridge in such a short barrel.
It's a nice barrel with fluting, chamber and threaded for the M700 but I might take a pass on this one...
Best.
Thanks for the responses. Nononsense, the reason I was considering this barrel was because, well I guess the cartridge intrigues me. In my 673 Remington in 6.5 Rem Mag, I bought some Berger VLD's in 130 grain, and also some Hornady 129 SST's, and basically they are useless. Not that they are useless, but when I seated them to 2.800", I could take the bullet and push it inside the case by hand because they were being seated into the ogive. Does that make sense? Anyway, my thinking is that I need a long action to take advantage of the long 6.5 bullets, and I have a Rem 700 adl in 7mm express, that while I like, I would be willing to put a nice 6.5 barrel on it in it's place. I don't know if I am thinking logically or not, but I like the 6.5 family of cartridges. Maybe I should just look for a 264 Win Mag, like the one I asked about in another thread. Thanks Again.
Instead of seating those bullets for the 673 to SAAMI or the bullet MFG spec, seat them to about 0.015-0.020 inches off the lands or so they will just barely fit and function in your magaxine well; which ever one is shorter. Most factory Remington chambers are long throated. Don't overlook the 6.5x55, 260 Remington, or the 6.5x284. There is little that the 6.5 Rem Mag, 6.5-06, or the 264 win Mag can do, that these will not, especially in a 24 inch length barrel. Another one that Nononsenseand others keeps under their hat that performs all out of proportion as it is efficient, is the 6.5 Heaton(basically a 25 WSSM necked up to 6.5)
Best
If you are saying you could push the bullet into the case by hand, your dies are not providing adequate neck tension when sizing the case. You can use thicker brass or size down from a larger caliber case to remedy this.
If the magazine won't allow seating in/at/near the lands, then you need a longer action/magazine length.
I use 8 twist in my 6.5 bores FWIW
I think you're just trying to use too long of a bullet for the magazine. Try a shorter ogive bullet that you will be hunting with, such as a Nosler, Sierra GK or Speer. The long ogive bullets you are talking about aren't hunting bullets, they are target bullets and pretty much need to be fed one at a time.