20 cals projectiles coming apart.

[CatShooter]

That's odd that the 39s wouldn't stabalize and the 40 Hornadys would, it's normally the other way around, the 40s need a 1-11 though some 1-12s will stabalize them, the 39s though onlt need a 1-12.

I was thinking the same thing....

 

[bowfisher]

Something is fishy. The 39 SBK's have shot great in my 12 tw,( Rock Creek) from 3900 to 4200, one of the best shooting bullets out there in 20 cal, IMO. Not all barrels will tolerate the 40 Vmax, but I have a 10tw Shilen that slings them very consistently at 4150fps.

I can't shoot the 39's fast enough in my 12 tw to blow them up. The 40 Nosler is a tougher pill also, IME..

 

[L-46]

That's odd that the 39s wouldn't stabalize and the 40 Hornadys would, it's normally the other way around, the 40s need a 1-11 though some 1-12s will stabalize them, the 39s though onlt need a 1-12.

I was thinking the same thing....

I though bearing surface or length had more to do with stability than weight?

 

[CatShooter]

That's odd that the 39s wouldn't stabalize and the 40 Hornadys would, it's normally the other way around, the 40s need a 1-11 though some 1-12s will stabalize them, the 39s though onlt need a 1-12.

I was thinking the same thing....

I though bearing surface or length had more to do with stability than weight?

Not bearing surface... but length is THE major factor and weight distribution is a minor factor.

The 40 is longer than the 39...

 

[L-46]

So the general consensus is,
both the 39 and 40's can take over 4500 fps and stay together.
No one has experienced failure unless the bore is heavily fouled?