Latest ubersplattendeaden cartridge from federal: the 7mm BC

[stagpanther]

The age of high pressure cartridges is upon us with federal's new cartridge (aka Fury done right). A few apparently strictly minor details are left out of the reviews I've read so far--like how reliably can the cases be reloaded (or will Federal be entering the die-making business imminently?) and who makes hardware that not only is proofed to the psi rating and added 15% safety buffer; but what that means in terms of expected barrel life.

[Unclenick]

If you make a drawing of your cartridge following SAAMI practices, any proof barrel maker can get a reamer made to those specs or use a CNC lathe with boring bars to chamber it. The proof loads themselves would then be developed on that pressure barrel to the SAAMI standard range, which is the same target percentage of the peak pressure MAP for all rifles, within the resolution of the standard readings. Any allowance for added over-pressure can be made with hoop stress analysis or finite element modeling. The one limitation will be that when one originates a cartridge, calibration has to be done as described in the SAAMI standard, so you don't get the average of multiple labs doing it that you do with SAAMI reference cartridges. That can cause some variation but would stay within 15% for a transducer barrel.

[stagpanther]

If you make a drawing of your cartridge following SAAMI practices, any proof barrel maker can get a reamer made to those specs or use a CNC lathe with boring bars to chamber it. The proof loads themselves would then be developed on that pressure barrel to the SAAMI standard range, which is the same target percentage of the peak pressure MAP for all rifles, within the resolution of the standard readings. Any allowance for added over-pressure can be made with hoop stress analysis or finite element modeling. The one limitation will be that when one originates a cartridge, calibration has to be done as described in the SAAMI standard, so you don't get the average of multiple labs doing it that you do with SAAMI reference cartridges. That can cause some variation but would stay within 15% for a transducer barrel.

Understood. I'll still wait a year and see how this pans out before jumping on the bandwagon. This new proprietary case metallurgy sounds a bit like magic fairy dust--but I give them credit for possible pushing the standards forward.

[steve4102]

According to Federal, barrel life is not affected by the increased pressure. They said the burning powder is the contributing factor not the amount of pressure

[stagpanther]

According to Federal, barrel life is not affected by the increased pressure. They said the burning powder is the contributing factor not the amount of pressure

Proprietary powder mix? I have my doubts this is going to be an "everyman's" easy conversion and easy reloading option--we'll see. Seems to me the marketing is aimed at the elite ultralight ultra long range hunter (i.e. rich) market.

[GeauxTide]

That's 7PRC. Not impressed with it. No way an 80,000psi cartridge doesn't affect barrel life, not withstanding steel cases. The 7STW provides the same performance at half the price.

[stagpanther]

No way an 80,000psi cartridge doesn't affect barrel life, not withstanding steel cases. The 7STW provides the same performance at half the price.

I was thinking maybe they came up with some freebore mitigation technique similar to what Weatherby does. But I agree, my simple logic tells me that this is going to be an overbore roaster lacking some new magic fairy dust formulation. I built a 7mmSTW and no matter how careful I am to pace my shots and minimize the round count per session--it is still an over bore blast furnace.

[ligonierbill]

I checked their website, and their stated intent is to deliver the velocity of current hot 7s out of a 20" barrel. I presume someone will deliver "backcountry" rifles that are light, compact, and expensive. As will be this ammo. Market? Certainly not us old tinkers. But I'm fixing to buy some outrageously expensive TSS shotgun ammo on the basis that I will never fire very many of them at turkeys. A hardcore "backcountry" hunter might look at this round the same way.

They describe their "proprietary steel alloy" as similar to that used in, among other things, nuclear reactors. Inconel came to mind: high strength at high temperature and corrosion resistant. Interesting, but personally I've regressed from 7mm Rem Mag to 7x57.

[stagpanther]

Market? Certainly not us old tinkers.

Most of the hunters I know buying those ultralight $4,000 backcountry rifles are old tinkers. God bless them, there's no other way I'd be able to try them out.

[44 AMP]

They describe their "proprietary steel alloy" as similar to that used in, among other things, nuclear reactors.

This statement means essentially nothing. Its just too broad and too vague to have value. First off, "as similar to" means what??

second, I've worked at nuclear reactors, there are all kinds of steel alloys used, from the pressure vessel and piping to the rebar in the office floor to the steel in the chain link perimeter fence.

IF one sets one's parameters widely enough, all steel alloys are "similar", from the reactor pressure vessel to the hull plates on the Titanic, if it is steel it can be described as similar, if you use broad enough terms.

[kilotanker22]

Originally Posted by GeauxTide

That's 7PRC. Not impressed with it. No way an 80,000psi cartridge doesn't affect barrel life, not withstanding steel cases. The 7STW provides the same performance at half the price.

It may have something to do with it. But before people get to thinking that overbore is due to pressure, let’s consider the cross sectional area of the bore, and the amount of powder being burned in it.

An easy comparison would be the 7mm Remington magnum vs the 7mm-08 Remington. Same bore diameter, same SAAMI pressure of 61,000psi. Which one do you think burns out a barrel faster? Obviously the answer here is the Remington magnum cartridge.

Using faster burn rate propellants in a 280 Remington sized case is likely how they are getting the 80,000psi. Same cross sectional area, less powder = better barrel life. Higher pressure and less ejecta means magnum performance from a shorter barrel with less recoil than cartridges of similar performance.

This is pure speculation on my part but I would bet that higher pressures will more easily yield consistent deflagration of the propellant. As a result yielding more consistent velocities, ES, and SD’s. I agree with most of the reviewers that higher pressure cartridges and materials are likely the future of ammunition.

[Sarge]

I am entirely satisfied with the old standards and will not be throwing time and money at this.

[stagpanther]

It may have something to do with it. But before people get to thinking that overbore is due to pressure, let’s consider the cross sectional area of the bore, and the amount of powder being burned in it.

An easy comparison would be the 7mm Remington magnum vs the 7mm-08 Remington. Same bore diameter, same SAAMI pressure of 61,000psi. Which one do you think burns out a barrel faster? Obviously the answer here is the Remington magnum cartridge.

Using faster burn rate propellants in a 280 Remington sized case is likely how they are getting the 80,000psi. Same cross sectional area, less powder = better barrel life. Higher pressure and less ejecta means magnum performance from a shorter barrel with less recoil than cartridges of similar performance.

This is pure speculation on my part but I would bet that higher pressures will more easily yield consistent deflagration of the propellant. As a result yielding more consistent velocities, ES, and SD’s. I agree with most of the reviewers that higher pressure cartridges and materials are likely the future of ammunition.

The flip side to that equation is how efficiently the system can handle the increased pressures--all barrel-life questions asides. That quicker propellant combustion is contained in a higher strength case--I'm not a physics inclined guy but my gut reaction is you're getting closer to the razor's edge of catastrophic failure when pushing the boundaries of fast-burning propellants and more strongly contained explosive reactions. I have no doubts it can be done safely within narrowly-defined standards--it's the at home reloader tinkering with custom loads that I think is going to be hard to reconcil with a development like this. But I'm happy someone else is willing to try--emphasis on someone else. As we used to say in the gliding flying community when weather conditions looked iffy--"Looks great! you go first."

[FITASC]

Here are some links (from posts on another site) about the Fed 7BC

https://gununiversity.com/7mm-backcountry-review/

https://www.federalpremium.com/backcountry.html

https://www.youtube.com/watch?v=G-cChdulaKY

https://www.outdoorlife.com/guns/fed...ountry-review/

[disseminator]

Looks interesting. I keep waiting for someone to announce the 7mm Creedmore (aka 7mm-08) but this looks like a 280 Remington on steroids.

The claims on the case tech are dubious.

We are supposed to believe the case itself is containing pressure that won't affect the chamber walls? Nonsense.

Let's detonate one outside of a chamber and see what happens, by there logic it will hold pressure and propel the bullet in the normal fashion. (Not happening)

I do love a (all) 7mm though, interesting cartridge but will go the way of the 7WSM IMO.

[Nathan]

Originally Posted by Sarge

I am entirely satisfied with the old standards and will not be throwing time and money at this.

Where is the like button?

[ligonierbill]

Further review indicates it's not as wild as it seems. The pressure problem they're addressing is not radial expansion "hoop" stress, but the axial expansion, the thing that locks up your bolt. The claim is that their new alloy case will remain in the elastic range under higher bolt thrust. It is reportedly a boron alloy steel. Boron as an alloy element improves workability, among other things, very important if you want to deep draw the material. (The nuclear reference is spurious - boron is a neutron absorber, so it improves shielding performance.) No special action is being used, just standard modern turn bolts. They even claim it is reloadable.

So I won't dismiss it.

[disseminator]

They even claim it is reloadable.

See below from the Outdoor Life article:

I know that RCBS is working on reloading dies for the 7 BC, and I’m eager to try them. But from what I’ve heard from RCBS, the dies are having trouble resizing the cases. In order to get them back to their original factory size they need to be run through the die multiple times — more than a dozen cycles, in fact.

Doesn't sound good.

[Unclenick]

Sounds like they'll require at least two dies used sequentially.

[stagpanther]

If the cases are that tough to resize--then it seems to me it will also be a struggle to maintain consistent neck-tension and concentricity. There's no free lunch as they say. But Federal may still have a viable market--none of the older hunters I know that are the ultralight long range hunters (which in my book is anything over 200 yards; but much longer in their's) are reloaders anyway.

[Pumpkin]

As far as resizing and trimming these cases, what type of equipment would you need? Someone mentioned Inconel as a possible case material, good luck trimming that stuff, a process more like grinding would probably be required.
I remember my first experience with it on an aircraft exhaust manifold, we had to have holes EDM’d on it before I could weld some bungs on it. It turned my carbide bit into a round blob.

And it makes me shudder to think about the potential “Hold my Beer” moments that could result from going cheap using something along the lines of fire formed 280 Rem brass

Is all this worth it to match the performance of some cartridges that are already available, I guess it’s progress though. I know I wouldn’t want any part of letting one of those bad boys rip out of a light weight rifle.

[disseminator]

I was thinking: this would be a great cartridge if they release a secondary spec with brass cased ammo at 65k PSI. New rifles and fast twists and 280 rem performance, could be a winner and you can run the hot stuff as you please.

[Unclenick]

Do we know the twist rate on the new rifle's barrel? Stability increases gradually with RPM, so it is not impossible that to prevent core stripping, they have slowed the rifling pitch too much for that lower pressure load concept. I just don't know.

[Jim Watson]

Berger says their 175 gr 7mm wants a 10 twist in conventional ammo which seems not unusual.

[disseminator]

I believe the spec is 1:8" Twist. Would easily cover any practical 7mm bullet we have.