Quarter bore and 6.5mm wildcat ???s

[Shawn Carlock]

Red,
I built a 6.5 STW for a client. It was an interesting round. I believe he is getting 3500 fps out of a 30" tube with 140 grain bullets. The 100 gr @ 4000 should be in your grasp. Tthe 6.5 STW is an easy brass build from 7 STW. I would build a 6.5 vs a .257 just based on bullet selecton. By the way I feel your pain of a gun safe that is not full.

Shawn

[Mikecr]

RedAllison
Just so ya know; the Scramjet case is completely different than the firebird/warbird case. The FB/WB case has 124grH2O capacity. The SJ has 95grH2O cap. Neither are based on, or derived from, a 416 case.
Given this, You'll gain nothing over the Scramjet using STW/300WBy cases, as they both have less capacity than the SJ.

With plenty of barrel, you could push a 90-100gr .257 bullet at ~3850, near max pressure. This with any case > 85gr cap. Beyond that, with light bullets anyway, there are no further gains with additional powder in this bore. Just heat and recoil.
With heavier bullets the extra capacity helps, but velocity drops.

Try the good old obsolete 6.5 Remington Mag
it will fool you.
Remington just screwed up with the short barrels and killed the cartrige with it
and now they are doing the same thing again
with all these new short mags coming out.
I built one with 26" barrel and chronagraphed 100 grain ballistic tips at
3700 FPS 60 grains of accurate 3100.
it out shoots my 264 mag and my 6.5-06 both
when it comes to FPS.