280 Rem Brass for 7mm Backcountry: A workaround idea

[Halligan]

Edit: for those just coming to the thread, others have made a compelling case to use 280 ai brass as a base, rather than 280 REM

Hi all,
I searched around here and the rest of the internet, so to my knowledge, this topic has not been brought up, and if I missed it, please post the link. As many of you are no doubt aware, the ability to reload the 7mm backcountry is still up in the air as reloading equipment, data, and processes are slow to roll out. This has been a cause for pause for many in the market for a new rifle (like yours truly), with the additional worry of ammo availability also cropping up.

This said, I got to thinking (I've been told this is dangerous by my girlfriend) and it occurred to me that the case is effectively a slightly modified 280 Rem. Therefore, if one could resize 280 Rem brass to 7mm backcountry dimensions, it would give owners of these rifles a much bigger pallet of load options that would be perfectly fine for big game hunting (just using published 280 load data).

Thus, two questions for the fine mad scientists here:
1) Would resizing the brass be doable (assuming yes based on specs, but I'm a novice in this realm)?
2) Do you think that you/others would be more comfortable buying into the cartridge now, knowing that there is a brass case "backup" option, which offers both perfectly adequate big game performance and protection against any steel case ammo shortages from Federal?

 

[khuber84]

You're gonna have inital trim them to 2.410, then push the shoulder/neck junction back with the 7bc die until they chamber with a lil bit of resistance(approx 0.060"), possibly trim again, then fireform. You just made about 0.060 of shoulder brass into neck brass. This new material will likely be thicker than the rest of neck brass. That'll need turned down to the same spec as the rest the neck to eliminate donuts and inconsistent neck tension. Cases that are blown out, will likely shorten up a fair bit due to brass displacement in the larger diameter shoulder area.

The 280 ackley diameters are much closer to the 7bc. I'd see if someone on the forum has a handful of old cases with loose primer pockets, you could test running them into the 7bc die, reshape the shoulder to 30° and push the shoulder neck junction back 0.040" till they chamber. Once again you'll need to neck turn the bottom of necks for consistency. You'll definitely want to put a good annealing on the case prior to doing this.

The 7bc has a few radius in the chamber that aren't present in other modern chambers, one at neck shoulder junction and one at shoulder body junction. I'm sure this is to help the case extraction with the high psi.

At the end of the day, you're now shooting a brass case designed for roughly max 65k psi. The new brass 7bc cases you made, affectively have less volume and now equal pressure rating as the 280 ackley you may have started with. Equal psi at less capacity equals less velocity. If you want brass cases, just buy a 280 ackley, it'll be much easier and it'll perform better than the brass 7bc cases.

 

[Scottf270]

The steel case is what allows the Backcountry to be what it is. While modifying regular brass cases may chamber, you are giving up the strength of the steel case. I see no gain at all and nothing but risk.

 

[pods8 (Rugged Stitching)]

I'd see if someone on the forum has a handful of old cases with loose primer pockets,

I definitely have some in my scrap pile if someone needed them.

 

[The Guide]

You're gonna have inital trim them to 2.410, then push the shoulder/neck junction back with the 7bc die until they chamber with a lil bit of resistance(approx 0.060"), possibly trim again, then fireform. You just made about 0.060 of shoulder brass into neck brass. This new material will likely be thicker than the rest of neck brass. That'll need turned down to the same spec as the rest the neck to eliminate donuts and inconsistent neck tension. Cases that are blown out, will likely shorten up a fair bit due to brass displacement in the larger diameter shoulder area.

The 280 ackley diameters are much closer to the 7bc. I'd see if someone on the forum has a handful of old cases with loose primer pockets, you could test running them into the 7bc die, reshape the shoulder to 30° and push the shoulder neck junction back 0.040" till they chamber. Once again you'll need to neck turn the bottom of necks for consistency. You'll definitely want to put a good annealing on the case prior to doing this.

The 7bc has a few radius in the chamber that aren't present in other modern chambers, one at neck shoulder junction and one at shoulder body junction. I'm sure this is to help the case extraction with the high psi.

At the end of the day, you're now shooting a brass case designed for roughly max 65k psi. The new brass 7bc cases you made, affectively have less volume and now equal pressure rating as the 280 ackley you may have started with. Equal psi at less capacity equals less velocity. If you want brass cases, just buy a 280 ackley, it'll be much easier and it'll perform better than the brass 7bc cases.

When I do my 7mm Backcountry review, I'll be firing some 280AI Hornady ammo (that my 280AI hates) through the rifle just to see if it can be done safely. I'll compare the speeds between my 280AI and the 7mm Backcountry using 280AI ammo. Hopefully I don't have to beat it open on my tailgate...

Jay

 

[TaperPin]

There’s not a lot of mystery between the two if you look at the chamber prints. I doubt a 280ai can be chambered in the BC since the neck/shoulder junction is .036” shorter in the BC. I wonder how die dimensions are different since it’s not designed for brass cases - does the new case material spring back less or more?

 

[khuber84]

That print for 7BC is fair bit different than the one I was looking at. Notice the radius ar shoulder and base of neck. Weird they're so different. Kinda have to trust your saami dimensions tho.

 

[Halligan]

You're gonna have inital trim them to 2.410, then push the shoulder/neck junction back with the 7bc die until they chamber with a lil bit of resistance(approx 0.060"), possibly trim again, then fireform. You just made about 0.060 of shoulder brass into neck brass. This new material will likely be thicker than the rest of neck brass. That'll need turned down to the same spec as the rest the neck to eliminate donuts and inconsistent neck tension. Cases that are blown out, will likely shorten up a fair bit due to brass displacement in the larger diameter shoulder area.

The 280 ackley diameters are much closer to the 7bc. I'd see if someone on the forum has a handful of old cases with loose primer pockets, you could test running them into the 7bc die, reshape the shoulder to 30° and push the shoulder neck junction back 0.040" till they chamber. Once again you'll need to neck turn the bottom of necks for consistency. You'll definitely want to put a good annealing on the case prior to doing this.

The 7bc has a few radius in the chamber that aren't present in other modern chambers, one at neck shoulder junction and one at shoulder body junction. I'm sure this is to help the case extraction with the high psi.

At the end of the day, you're now shooting a brass case designed for roughly max 65k psi. The new brass 7bc cases you made, affectively have less volume and now equal pressure rating as the 280 ackley you may have started with. Equal psi at less capacity equals less velocity. If you want brass cases, just buy a 280 ackley, it'll be much easier and it'll perform better than the brass 7bc cases.

Okay that makes sense, from my quick overview of the saami specs, it initially seemed as though 280 rem brass may need less movement.

@Scottf270, I don’t see the risk of using 280 REM/Ai load data, unless somehow the engineers decided to rely so much on the strength of the steel case, that they weakened the actions/barrel pressure ratings. I find that unlikely.

@The Guide, definitely interested to see your results

Now, with this all being said, do any of you think there would be a market for 7 backcountry brass cases? I personally think so, but want to hear your thoughts

 

[khuber84]

Okay that makes sense, from my quick overview of the saami specs, it initially seemed as though 280 rem brass may need less movement.

@Scottf270, I don’t see the risk of using 280 REM/Ai load data, unless somehow the engineers decided to rely so much on the strength of the steel case, that they weakened the actions/barrel pressure ratings. I find that unlikely.

@The Guide, definitely interested to see your results

Now, with this all being said, do any of you think there would be a market for 7 backcountry brass cases? I personally think so, but want to hear your thoughts

I'd use minimalstarting load(maybe 5% less) weight charges to form brass. The start with minim 280ai charges. The steel cases likely hold a fair bit more powder than a brass equivalent.

I see no point in brass 7bc cases, as it really neuters the performance, and completely alienates the original intent, purpose, and marketing of the planned objective.

If you want brass cases, shoot a 280 ackley on a good custom action with Peterson brass. That combo will likely run 70-75k psi all day. Granted you might lose primer pockets in 2-3 firings, but at this point 7bc brass isn't even reloadable. It'll be close to the 7bc.

 

[pods8 (Rugged Stitching)]

I wonder how die dimensions are different since it’s not designed for brass cases - does the new case material spring back less or more?

What dies? Did they finally figure anything out? Last info I noticed was they were unsuccessfully trying to figure out how it could be resized for reloading.

 

[pods8 (Rugged Stitching)]

Granted you might lose primer pockets in 2-3 firings,

Its a right of passage with a 280ai...

 

[TaperPin]

What dies? Did they finally figure anything out? Last info I noticed was they were unsuccessfully trying to figure out how it could be resized for reloading.

That was said assuming they will eventually have dies readily available. Right now reamers can be ordered for custom dies and I thought a number of die manufacturers have part numbers for BC dies, even if they aren’t available. It wouldn’t surprise me if the high pressure reloading part falls flat on its face since many guys struggle with much better understood brass cases.

 

[pods8 (Rugged Stitching)]

That was said assuming they will eventually have dies readily available. Right now reamers can be ordered for custom dies and I thought a number of die manufacturers have part numbers for BC dies, even if they aren’t available. It wouldn’t surprise me if the high pressure reloading part falls flat on its face since many guys struggle with much better understood brass cases.

Gotcha, seemed like your prior comment was present tense vs future speculations.