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.

 

[K.E.C. Darkside]

I built a 270 - 08 and I'm getting 3000fps comfortably with 133 Apex Afterburner with Rl-17, Lapua brass, Fed-210m, with
Coal 2.910.
95gr.TTSX with IMR8208XBR 3330fps
Lapua brass, Fed-210m, 2.669coal.
Built on a 110 Savage action, 26" barrel.

I have 600 pieces of 277 Fury brass and one of these days I would like to build one. But I'm having a lot of Fun with the
27-08.
If you want one build it.

 

[Lou270]

Reposted

 

[Lou270]

Why they went with 1-10 in Cross and 1-7 in Spear is beyond me. Any case, it will stabilize any of the 1-10 stuff there for regular 270. For ex the factory hybrid ammo is loaded with a 150 AB (bc of .5) and there is a 277 fury 155 Sierra Matchking load with bc in mid .5s.

Very curious to see what others in bolt market pick this up. The fact there is now a match load with matchking makes me think there is some sniper applications coming up.

Lou

 

[med358-boise]

I built a 270 - 08 and I'm getting 3000fps comfortably with 133 Apex Afterburner with Rl-17, Lapua brass, Fed-210m, with
Coal 2.910.
95gr.TTSX with IMR8208XBR 3330fps
Lapua brass, Fed-210m, 2.669coal.
Built on a 110 Savage action, 26" barrel.

I have 600 pieces of 277 Fury brass and one of these days I would like to build one. But I'm having a lot of Fun with the
27-08.
If you want one build it.

K.E.C,

That is very encouraging. Hard to estimate potential velocity just via extrapolation and I purposefully went conservative.

Couple of follow-up questions:

1) is your 270-08 "regular: or improved?
2) Ever do any development with H4350, Varget, or CFE-223?

 

[K.E.C. Darkside]

K.E.C,

That is very encouraging. Hard to estimate potential velocity just via extrapolation and I purposefully went conservative.

Couple of follow-up questions:

1) is your 270-08 "regular: or improved?
2) Ever do any development with H4350, Varget, or CFE-223?

I settled on 270-08 regular. I was going to go improved, but I started finding Fury brass. I had already had a reamer ordered for the regular and went through a handful of meetings with JGS on the spec's. So I figured I would do what I ordered and if I liked it keep it and plan on a Fury in the future. And I do like it, have taken a couple whitetail and a handful of groundhogs. I have had it out to 600yds at the range 3/4 moa for now, still need a little work. Out to 300yds it's 1/2moa.
Still working on loads and bullets.
The powders you mentioned work well.
Hope this helps.

 

[akmtnhnt]

I built a 270 - 08 and I'm getting 3000fps comfortably with 133 Apex Afterburner with Rl-17, Lapua brass, Fed-210m, with
Coal 2.910.
95gr.TTSX with IMR8208XBR 3330fps
Lapua brass, Fed-210m, 2.669coal.
Built on a 110 Savage action, 26" barrel.

I have 600 pieces of 277 Fury brass and one of these days I would like to build one. But I'm having a lot of Fun with the
27-08.
If you want one build it.

That's perfectly in line with the brass case furry. You might pick up 30-40fps with the fury, but not much.