Interesting. Very interesting. 7BC doesnt fill any exact needs for me, but.... i like ballistics tech getting pushed forward. Bolt action rifle pressures been basically static for.... well, maybe 100 years? Forever in modern world terms
This tech (steel cases) seems more promising then the hybrid cases... which had felt like maybe good solution... until i saw those chamber erosion issues!! (Thanks for showing that). Unless they can figure out way to stop that gas leakage, im guessing that will probably be the thing that kills that concept. High pressure gas is so erosive... nitriding might slow it, maybe enough, but am guessing it would just buy time... whether enough time is big question (hate to wear out chamber while rifling is still usable).
Prob need something even more erosion resistant... stuff you just dont see in commercial barrels... like stellite maybe. Or some sort of ceramic magic material? Really they just need to fix the leakage issue. I do wonder how its going for the military... lots of complaints about .277, but this is one i havent heard.
so .008" bigger shoulder than 280 AI, which means half the case taper (280 ai looks like about .015" taper). I wonder what bolt thrust is like on 7BC? 80k steel case vs 65k brass case in 7BC. Or 65k in brass case 280 AI. Am guessing the more straightwall case of 7BC is bc steel is more elastic then brass, so it backs off chamber wall more after firing, so doesnt need as much case taper to aid extraction. Of course, it sounds like full power 65k brass case 7BC isnt sticking either.
I DO wonder about about the bolt thrust though. So many things impact it though (strength of case, friction coefficent of case, how rough chamber wall is, presence of any coatings, any lube / oil / water etc on case/ chamber... etc etc). And getting real world numbers on actual bolt thrust prob takes some nice equipment, i dont think its nearly as simple as a piezo strain gauge on chamber wall of barrel (like reading chamber pressure).
Trying to ballpark bolt thrust is my way of asking... how much harder is the action being run w full pressure 7BC (80k steel case)? I wonder how much closer things might be to lug setback? Of course that depends on action/bolt materials, hardness, lug size, etc etc. At minimum id just think you were running w less safety margin in case of "pressure excursion". Like powder overload/ wrong powder, Bore obstruction, things like that.
I do know that the thing that really kills actions is when case head lets go and basically vents all the gas into action interior. Give gas thats at 75k + lose inside action where it now has several inches of square area to act on... thats when things come apart. Mags blown out, stocks broken, at some point (probably getting into the 100k+ range) actions split, generally wrecked, barrels blown out of action, etc etc. All the classic rifle kabooms where rifle is just in pieces.
Some actions handle that way better than others (something w a cone breech / unsupported case head like 03 springfield be worse about this), actions w fully supported case heads handle those situations better. Nit sure what actions are being used in current 7BC factory rifles, so not throwing any shade there. I just know if i was playing w this id want action that was goid at supporting case head /dealing w gas containment/relief. That steel case should resist popping better than brass case (just about the whole point if the steel case), but if case DOES vent/rupture, it will be worse at 80k then at 65k.
Not saying any of this to throw any shade on 7BC... just sharing thoughts/questions that pop up in my head. So whether those are the right questions is a whole different issue. And none of them are answers either.
All new tech has teething issues / potential downfalls. Sounds like 7BC is a much more actually workable concept then the other 80k cartridge ideas that have come out lately.
Who knows, maybe 10 or 20 years from now 80k cartridges will be all over the place and used by the majority of people competing at a high level in PRS, or hunters looking for max performance.
Either way, thanks for sharing 45-90. Will be interested in seeing how this continues to develop
This tech (steel cases) seems more promising then the hybrid cases... which had felt like maybe good solution... until i saw those chamber erosion issues!! (Thanks for showing that). Unless they can figure out way to stop that gas leakage, im guessing that will probably be the thing that kills that concept. High pressure gas is so erosive... nitriding might slow it, maybe enough, but am guessing it would just buy time... whether enough time is big question (hate to wear out chamber while rifling is still usable).
Prob need something even more erosion resistant... stuff you just dont see in commercial barrels... like stellite maybe. Or some sort of ceramic magic material? Really they just need to fix the leakage issue. I do wonder how its going for the military... lots of complaints about .277, but this is one i havent heard.
so .008" bigger shoulder than 280 AI, which means half the case taper (280 ai looks like about .015" taper). I wonder what bolt thrust is like on 7BC? 80k steel case vs 65k brass case in 7BC. Or 65k in brass case 280 AI. Am guessing the more straightwall case of 7BC is bc steel is more elastic then brass, so it backs off chamber wall more after firing, so doesnt need as much case taper to aid extraction. Of course, it sounds like full power 65k brass case 7BC isnt sticking either.
I DO wonder about about the bolt thrust though. So many things impact it though (strength of case, friction coefficent of case, how rough chamber wall is, presence of any coatings, any lube / oil / water etc on case/ chamber... etc etc). And getting real world numbers on actual bolt thrust prob takes some nice equipment, i dont think its nearly as simple as a piezo strain gauge on chamber wall of barrel (like reading chamber pressure).
Trying to ballpark bolt thrust is my way of asking... how much harder is the action being run w full pressure 7BC (80k steel case)? I wonder how much closer things might be to lug setback? Of course that depends on action/bolt materials, hardness, lug size, etc etc. At minimum id just think you were running w less safety margin in case of "pressure excursion". Like powder overload/ wrong powder, Bore obstruction, things like that.
I do know that the thing that really kills actions is when case head lets go and basically vents all the gas into action interior. Give gas thats at 75k + lose inside action where it now has several inches of square area to act on... thats when things come apart. Mags blown out, stocks broken, at some point (probably getting into the 100k+ range) actions split, generally wrecked, barrels blown out of action, etc etc. All the classic rifle kabooms where rifle is just in pieces.
Some actions handle that way better than others (something w a cone breech / unsupported case head like 03 springfield be worse about this), actions w fully supported case heads handle those situations better. Nit sure what actions are being used in current 7BC factory rifles, so not throwing any shade there. I just know if i was playing w this id want action that was goid at supporting case head /dealing w gas containment/relief. That steel case should resist popping better than brass case (just about the whole point if the steel case), but if case DOES vent/rupture, it will be worse at 80k then at 65k.
Not saying any of this to throw any shade on 7BC... just sharing thoughts/questions that pop up in my head. So whether those are the right questions is a whole different issue. And none of them are answers either.
All new tech has teething issues / potential downfalls. Sounds like 7BC is a much more actually workable concept then the other 80k cartridge ideas that have come out lately.
Who knows, maybe 10 or 20 years from now 80k cartridges will be all over the place and used by the majority of people competing at a high level in PRS, or hunters looking for max performance.
Either way, thanks for sharing 45-90. Will be interested in seeing how this continues to develop
