Author Topic: Cast and barrel twist rate  (Read 691 times)

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Offline crash87

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Cast and barrel twist rate
« on: November 25, 2007, 05:46:42 AM »
Veral,
       A number of years ago I had a Winchester '95 rebored to a 35 Whelen. My idea at the time was to have an affordable rifle and ammo  somewhat equal the .405 Win., in velocity and bullet weight anyway. Remember at that time the .405 was a forgotten household word. I had it rifled to a 1:12 twist basically to stabalize a jacketed 300 gr bullet. I never did fire those 300 grainers and basically stuck with jacketed 250's. In my readings over the years, the basic consensus is to use a slower twist when using cast, in this case 1;14 or better yet (better?) a 1:16. It is was said that a faster twist would strip the bullet. My definition of that would be, that it would not grip the rifling and skid a ways, until, it grabbed, unless of course you would slow it down to alleviate this from happening.
       A while back you cut me what you termed a Modified LCFN for my .416 Rigby, a LCFN with the metplat diameter the same as a LFN. This bullet style is what I envision for this .35 Whelen. I would also like it to be as close to 250 grains as possible, for no other reason, that is what I vision to be right for my rifle and the game I intend to, hunt. Can I expect to get Whelen velocities with the 1:12 twist?, or will I have a duplicate of a .35 Winchester?, (which isnt all that bad either). Also, what has you experimentation's concluded to, as results from shooting cast bullets in different twist rates?
       If you already have'nt figued it out, I am looking for the difinitive answer to what "has" been written on this subject of to fast versus to slow of twist for a cast bullet. Thank You CRASH87

Offline Veral

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Re: Cast and barrel twist rate
« Reply #1 on: November 29, 2007, 03:17:02 PM »
  Regarding what "has" been written (by has been writers?), about twist rate with cast vs. jacketed.  People write their experiences, but almost all cast bullet experiences are written without a through understanding of bullet design and or ability to change it.  Lubrication, ditto.
  Shoot whatever weight you want at whatever speed / pressure your gun can handle, IF, the bullet is an LBT design, LBT lube is used and if the barrel is lapped if need be.  I believe even a 1-16 twist would shoot fine, or a one in 8 or 9 on the high end would not strip the rifling. 

  Stripping on the rifling is caused by rough leading edges of the rifling, poor lubrication, poor gas check shank fit and to some degree bullet hardness not being high enough, but this latter would not be an issue with Whelen 250 gr bullet loads if hardness is at least 124-14 bhn.  All these factors apply to all bullet lubes, but LBT lube is far more forgiving of soft bullets than any other lube I know of..
Veral Smith