277 Fury 1:10 Twist rate am I missing something

[med358-boise]

So seriously considering buying a Sig Cross comes with a 20" in barrel with a 1:10 twist rate. I always reload for everything. So I look at the factory the spec for the sig (non-hybrid) ammo and the ammo is 2710 to 2750, for 130-150. So add say 80 fps to be on the safe side, for a 20 inch bbl and most every 140ish range with a decent BC is coming up unstable. Yes, I am aware that it is bullet length that drives stability and that is what I am using to enter into calculators.

Am I missing something? Am I suffering a senior moment?

 

[xsn10s]

Yeah I think your inputs must be off. I just did Berger's Barrel Twist calculator and the 140gr hunting VLD was fine at sea level and 2650 fps. https://bergerbullets.com/twist-rate-calculator/

 

[cohunt]

Barrel twist was set for the hybrid ammo as it pushes 3000 iirc, you might need to drop to 130gr bullets

I load 130gr bullets in 6.8spc 1:11 twist 16" & 20" at 2550-2700 ( loaded long with "special" powder) and they are stable at my altitude, 140s wont stabilize in 1:11@ 6.8spc speeds--- I would think you could get a 140 stable in 1:10 with that case as it holds at least 10 grains more than a 6.8spc does

 

[akmtnhnt]

Sig completely screwed the pooch with the 277 fury cross. The SAAMI spec that they submitted is 1-7. They completely neutered the cartridge in that rifle buy doing 1-10.
I doubt anyone else is going to launch a rifle in that cartridge so that'll be the nail in it's coffin from the civilian side.

It's too bad as I really like the cartridge. I've been shooting it for almost 2 years now in a custom barrel. I was going to buy the cross as soon as the 277 cambering was released, but there's no chance I'd own what they have for sale.

 

[med358-boise]

Sig completely screwed the pooch with the 277 fury cross. The SAAMI spec that they submitted is 1-7. They completely neutered the cartridge in that rifle buy doing 1-10.
I doubt anyone else is going to launch a rifle in that cartridge so that'll be the nail in it's coffin from the civilian side.

It's too bad as I really like the cartridge. I've been shooting it for almost 2 years now in a custom barrel. I was going to buy the cross as soon as the 277 cambering was released, but there's no chance I'd own what they have for sale.

I was hoping to use mono-metals and I know copper bullets are longer but about the only thing that I can find that stabilzes is Barnes 130 with sub .4 BC

 

[K.E.C. Darkside]

I would recommend that you build what you want. With a 8twt barrel and a throated reamer for the bullets you want to shoot. You can still get brass for the
277 Fury, don't know how long it will be available. And you can still shoot factory ammo if you want to.
Hope this helps.

 

[med358-boise]

I would recommend that you build what you want. With a 8twt barrel and a throated reamer for the bullets you want to shoot. You can still get brass for the
277 Fury, don't know how long it will be available. And you can still shoot factory ammo if you want to.
Hope this helps.

I will likely pass on the whole thing. I really like the idea of the Sig Cross with the folding stock/chassis look for just a little more than a lightweight folding chassis and not 6 months of lead time and you get a "cool" cartridge.

But if I build my own with a 1:8 twist and a lightweight folding stock/chassis it's not worth the extra money to me and if I don't go folding stock and go 1:8 twist I am end up with essentially a 284 winchester which I already have.

 

[med358-boise]

The results of my conservative stabilization calcs were that with expected velocities for 130 grain bullets in the low to mid 2800s that mono-metals and copper jacketed lead would all be fine and the 140s in the low to mid 2700s will be limited to copper jacketed lead. I used 10 deg F as my temps. Velocities might be a little conservative but better safe than sorry.