1-18 tw 30 cal and 125 gr pills

[GT Accuracy]

as mentioned in title - anyone try it? Thinking about 125 gr b-tips in a 300 varminter. Know i can get it done in a 17 but anyone do an 18?

 

[Todd DuBose]

Greg, Im doing a 30/378 Weatherby, with 125 gr. Ballistic Tips in a 1-13" twist Bartlein 31" barrel and at 103,0 grs. 4350 and Federal 215 Match Grade primers, My chrono is showing 4,035-4,048. I switched bores now and am having a try in the .257 STW-1-12" twist, Thinking about the Hornady 75 gr. V-Max and the Nosler 85 gr. Ballistic Tip... And Yes, I am Very Aware of how short Barrel Life will be. Thats why there are So Many Great!! Barrel Makers!! Give me a Break... Dont let anyone talk you out of it and just Grin Real Big when you get to see the Destruction of the Magic... 4,000!! Im 58 years old, Have had 4 heart attacks and Love to Live Life on the Wild... Side!! Go for It!! Enjoy what you learn from it and remember to Grin everytime you think about what I said!! PO Ackley started me off with the 220 Swift about 42 years ago and I have Always had fun doing it on the High Velocity Side!! Im getting off my soap box and giving the floor to the More Modest?? Well, Maybe More Sane?? People that will tell you, You are wasting money and this cartridge or that one is so much more economical!! I call BS!! Your Money and Your Fun!!

 

[scope eye]

At 3800 Fps the 17 twist is spinning the bullet 160,000 rpm, and at 4000 fps the 18 twist would be spinning the bullet 160,000 rpm, both are attainable so yes. I have a 17 twist 30" Bartlein 300 RUM.

Dean

 

[GT Accuracy]

ooooo this is gonna be fun....i'll post some numbers and build videos when the barrel arrives

 

[RGRobinett]

as mentioned in title - anyone try it? Thinking about 125 gr b-tips in a 300 varminter. Know i can get it done in a 17 but anyone do an 18?

For polymer tipped, BT bullets, you'll be better of with the 1:17" twist; having not, "done the math", depending upon [125Gr. b-tip] length, even the 17" twist may prove marginal. For a FB bullet, anything over 1.050" long results in less than desirable gyroscopic stability: Sg <1.4. As compared to a FB HP, of equal weight, but SHORTER, the combination of BT (reduced drag) & plastic tip (equals more LENGTH), may require 2" + faster twist. Good shootin'! RG

 

[fredo]

Required twist is calculated via a bullet's bearing surface. IE, the actual length of the bullet that engages the barrel's rifling.
Tip style & overall length have nothing to do with it...

 

[JRS]

Required twist is calculated via a bullet's bearing surface. IE, the actual length of the bullet that engages the barrel's rifling.
Tip style & overall length have nothing to do with it...

Actually, as is usually the case, the good RG is correct once again 8)

 

[fredo]

Would appreciate a reference to a stability calculator where bullet tip type is listed as a quantifying factor?

IE, two bullets of equal weight, bearing surface & overall length...but one has a polymer tip and the other has a standard small HP meplat. Am I to be led to believe that that polymer tipped bullet requires a different twist rate???

 

[JRS]

Re-read the response posted by Randy Robinett.

 

[fredo]

Reckon I was both oversimplifying & generalizing at the same time when I mis-typed.
Apologies...