Thoughts on New Federal 7mm Back Country

[pavementends]

If the dire predictions come true and you buy/build a 20" 7BC and Federal stops producing cases What are you left with? A build that is essentially a lightly modified .280 when using brass cases. Then you can search all the posts asking about a short barreled 280/280AI. All the benefits of a 30/06 head size, fast twist barrel throated for long bullets. Hardly the end of the world.

 

[ImBillT]

Actions will be fine...it's just now Federal is being honest that they are running 80k...Sherman's have been running that since they came out, just no published data on them.

I was wondering this myself. If f the primers are the same, and you're really flattening or have perhaps even pierced a primer, then either Federal is using different primer cups, or the new case isn't doing anything that some of us haven't already done.

There are predominately 2 kinds of rifle usage in the US for hunting with those in the east hunting forest country and shooting deer at 30/30 ranges and western hunters who have more opportunity for extended ranges in more open country, where longer barrels are less an inhibitor. My personal experience includes both.

I have a 22" Featherweight in 280AI and have loaded extensively for it over the last decade or so. That is my baseline.

To get 80kpsi from a reported 60ish grains of powder can only come from 2 methods, unspoken at this time:

1. Using a proprietary powder unknown and unavailable to the ballistic world...

2. By using a custom designed cartridge case that includes increased internal webbing at least in the base area so that that 60 grains is very restricted - causing that 80k pressure.
.

This is just not true. Most reloaders are shooting powders in the 4831 and slower range in a 280ai. You could go to 80ksi and far beyond simply by switching a faster burning powder. 60gr of 4350 would likely far exceed 65ksi behind a 175 in 280ai. The problem? Your brass case won't contain it. Once the seal is broken, terrible things happen. The action can handle the pressure, but it's the case that seals the gasses in. I suspect you could load well in excess of 80ksi with on the shelf powders.

 

[ImBillT]

Here's what we should all ACTUALLY be asking.

If these cases can be reloaded, and primers that can take the presser are available, why not use them for your rifle that's already chambered for 30-06, 280ai etc?

Not a suggestion. Try that at your own risk.

 

[AussieWriter]

I was wondering this myself. If f the primers are the same, and you're really flattening or have perhaps even pierced a primer, then either Federal is using different primer cups, or the new case isn't doing anything that some of us haven't already done.


This is just not true. Most reloaders are shooting powders in the 4831 and slower range in a 280ai. You could go to 80ksi and far beyond simply by switching a faster burning powder. 60gr of 4350 would likely far exceed 65ksi behind a 175 in 280ai. The problem? Your brass case won't contain it. Once the seal is broken, terrible things happen. The action can handle the pressure, but it's the case that seals the gasses in. I suspect you could load well in excess of 80ksi with on the shelf powders.

Don't twist what I said!
If I am wrong, name a third way 60grains of powder could generate 80kpsi.
Waiting............

 

[ImBillT]

Don't twist what I said!
If I am wrong, name a third way 60grains of powder could generate 80kpsi.
Waiting...........

The first paragraph didn't belong. I was typing that in response to someone else and never submitted it.

The part about simply requiring a SLIGHTLY faster powder is easily provable.

Below are three screenshots calculating velocity and pressure using a case with the same volume as a 280ai and 60gr of three different Hodgdon powders. You can see that switching from 4831 to 4350 goes from a safe pressure to a pressure that would be dangerous in a brass case. 81ksi in fact. And 4350 is still a relatively slow burning powder. The third, with H4895, would not even calculate due to being over 100ksi as noted in the error message at the bottom.

I use a similar load behind 190gr VLD's in a 30-06AI.

 

[AussieWriter]

The first paragraph didn't belong. I was typing that in response to someone else and never submitted it.

The part about simply requiring a SLIGHTLY faster powder is easily provable.

Below are three screenshots calculating velocity and pressure using a case with the same volume as a 280ai and 60gr of three different Hodgdon powders. You can see that switching from 4831 to 4350 goes from a safe pressure to a pressure that would be dangerous in a brass case. 81ksi in fact. And 4350 is still a relatively slow burning powder. The third, with H4895, would not even calculate due to being over 100ksi as noted in the error message at the bottom.

I use a similar load behind 190gr VLD's in a 30-06AI.

I considered that as have used H 4350 which is AR 2209 since it was created and long before it was imported to the US.

I think you may be onto something here as it makes the most sence, certainly more than Federal creating a new proprietary powder.

If a faster burning powder is used, its needs to be a consistently reliable batch to batch consistency to maintain reliability as factory ammo needs. H 4350 is as good as powder gets and is temperature insensative so the plusses keep adding up.

So we come back to the case. We need the hype to die as it is not constructive. Wr need a case cut in half so we can see the internal construction and volume.

I think an ordinary current manufactured action would be fine as testing has already exceeded 100kpsi with brass cases.

50 years ago, Roy Weatherby Snr stuffed a 180grain bullet in the bore and fired a 300 Weatherby cartridge and failed to damage the action. Not all actions are as strong as a Mark V but a steel case makes the old addage "4 rings of steel" which could be all the difference and your reference to H 4350.is a good call for that.

Thanks for the follow up comments.