.277,140gr 3000fps+ in a 16" bbl @ 80000psi

[jfloyd]

I'm curious why they are are so stuck on the 16" barrel. If it's overall length of the platform, you can go bullpup and have a much longer barrel for ballistics purposes and still be in a "standard" chambering that can far exceed the 140 grain bullet at 3000fps. Seems like an answer to a question nobody had asked until SIG or the military decided this is a must have capability. Barrel life and the potential of failure with a three piece case design would be a major concern as well. Dissimilar metals of the case over years of storage could easily lead to case separation and get a person killed in a battle with half the case still in the chamber. Maybe it will be the greatest thing ever but count me skeptical.

 

[J E Custom]

Sometime we tend to over think a need or problem and spend lots of time just to end up with nothing we don't already have. It goes against the rule of "Less is better/more" and the more complicated you make something the more problems you will have.

J E CUSTOM

 

[redneckdan]

I'm most interested in seeing how the cases hold up. I'd be interested to see if it can be applied to standard pressure calibers to give more primer pocket longevity. Imagine buying 100 .300 win mag cases and running them at full power the whole useable life of a barrel.

I'm aware of some research in 'joining' of dissimilar metals being done, there are NDAs in effect that limit what can be shared. The results are pretty impressive. When I first saw it 5 or 6 years ago one of my thoughts was hmmm, wouldn't it be cool to stick a stainless head on a brass case?

 

[redneckdan]

Sometime we tend to over think a need or problem and spend lots of time just to end up with nothing we don't already have. It goes against the rule of "Less is better/more" and the more complicated you make something the more problems you will have.

J E CUSTOM

Sounds good, lets go back to the world before 4831 was available...or heck, let's step it back to the 45-70

 

[John Polk]

There are plenty of actions that will handle the pressure. But there are many other problems that will crop up at those pressures. Velocity is not an issue on something like this, But throat erosion and heat cracking/ checking will be.

One of the things that I noticed with the high pressure loading's was the throat erosion and the need to set the chamber back after only a few hundred rounds to regain accuracy. this was the main reason I purchased a bore scope so I could see/follow the progress of erosion in the throat.

In these experimental loading's, I found chambers/throats lasted only 2 or 3 hundred rounds but the bore remained good for 12 to 1500 rounds before it was used up. When I backed off the pressure (From 75,000 to 65,000 I noticed a huge difference if throat life. When I went to 63,000 Psi max, the chambers and throats performed normally and life was restored to thousands of rounds. that Is when I decided to stay below 63,000 by going to more slow burning powder and larger case capacity to get the desired velocity.

The extra powder cost a little more but was cheaper in the long run by saving components, barrels and actions. The use of more efficient case designs also aided in this improvement.

Buy or build what you want and live with your decision as I did. One of the advantages of age is that you don't make the same mistake twice. (I had not listened to my own advice and it took several times to figure out that Pressure is the enemy of longevity.

J E CUSTOM

That and the same

There are plenty of actions that will handle the pressure. But there are many other problems that will crop up at those pressures. Velocity is not an issue on something like this, But throat erosion and heat cracking/ checking will be.

One of the things that I noticed with the high pressure loading's was the throat erosion and the need to set the chamber back after only a few hundred rounds to regain accuracy. this was the main reason I purchased a bore scope so I could see/follow the progress of erosion in the throat.

In these experimental loading's, I found chambers/throats lasted only 2 or 3 hundred rounds but the bore remained good for 12 to 1500 rounds before it was used up. When I backed off the pressure (From 75,000 to 65,000 I noticed a huge difference if throat life. When I went to 63,000 Psi max, the chambers and throats performed normally and life was restored to thousands of rounds. that Is when I decided to stay below 63,000 by going to more slow burning powder and larger case capacity to get the desired velocity.

The extra powder cost a little more but was cheaper in the long run by saving components, barrels and actions. The use of more efficient case designs also aided in this improvement.

Buy or build what you want and live with your decision as I did. One of the advantages of age is that you don't make the same mistake twice. (I had not listened to my own advice and it took several times to figure out that Pressure is the enemy of longevity.

J E CUSTOM

Do you recommend 63000 psi as a maximum pressure in the rifles we normally use?

 

[J E Custom]

That and the same

Do you recommend 63000 psi as a maximum pressure in the rifles we normally use?

Yes I do . I have found that 62 or 63,000 Psi seem to be an ideal all round pressure for longer life and it gives up very little usable velocity. even though 65,000 may be the SAMMI max, that Is just what it means MAX and it does not mean ideal.

J E CUSTOM

 

[Craig Miller]

I'm curious why they are are so stuck on the 16" barrel. If it's overall length of the platform, you can go bullpup and have a much longer barrel for ballistics purposes and still be in a "standard" chambering that can far exceed the 140 grain bullet at 3000fps. Seems like an answer to a question nobody had asked until SIG or the military decided this is a must have capability. Barrel life and the potential of failure with a three piece case design would be a major concern as well. Dissimilar metals of the case over years of storage could easily lead to case separation and get a person killed in a battle with half the case still in the chamber. Maybe it will be the greatest thing ever but count me skeptical.

Everything for this cartridge is built around the Army's requirement that whatever the final vendor (currently 3 competing) comes up with, it has to push an Army designed 135gr .277 caliber armor piercing bullet at 3k out of a carbine barrel.

I'm more interested in the CROSS rifle platform itself. I've wanted a rifle like this that was reasonably priced and used AICS mags (both not features of Q's The Fix). Now will it be able to swap barrels so I can have both a light 6.5CM or something for targets/deer-sized game and a short mag for elk, etc. That's the question I want answered.

 

[adam32]

Yes I do . I have found that 62 or 63,000 Psi seem to be an ideal all round pressure for longer life and it gives up very little usable velocity. even though 65,000 may be the SAMMI max, that Is just what it means MAX and it does not mean ideal.

J E CUSTOM

Longer life for the casing or for the barrel?

 

[J E Custom]

Longer life for the casing or for the barrel?

Everything ! Barrel bore, throat, action, cases, recoil lugs, bedding ETC.

J E CUSTOM

 

[adam32]

Everything ! Barrel bore, throat, action, cases, recoil lugs, bedding ETC.

J E CUSTOM

So a .308 Win running 63k and a 22-243 running 63k will have the same barrel life, case life, etc?

 

[highdrum]

I think a 308 sized case @ 80k psi isn't any different than a sherman short case running @ 72K, which I'm sure plenty do with the velocity they get. I doubt barrel wear will be any worse than a 270wsm.

 

[Don A Parsons]

When i thought of pressures exceeding 50 to 55.000 it seemed like alot,,, it makes wonder if there is any extra hot flash burn on the throat of the barrel with those pressures...

62.300 in pressure could push temps into the 1600 degrees for that split seconds,,, hopefully this new action and cartridges along with the barrels can withstand this over the period of its life...

I'm glad my off season plinking loads run in the 55 ish bracket,,, I get to turn up the heat when hunting season gets underway... Ha...

 

[J E Custom]

So a .308 Win running 63k and a 22-243 running 63k will have the same barrel life, case life, etc?

I wouldn't go that far because of different barrels, loads, bullets and cleaning regiments. But they should last longer than if pushed to 65,000 or 70,000 Psi like so many people do trying to make a cartridge do more than it was designed to do.

Once I lowered my max pressure below 63,000 psi, I have yet to shoot a barrel out. And never had to set the shoulder back. So there is some benefit to running lower than Max pressures.

Its like running an engine at full throttle all the time as compared to rarely, The engine will last a long time as apposed to a few hours.

Just saying don't push the cartridge beyond it's ability.

J E CUSTOM

 

[J E Custom]

I think a 308 sized case @ 80k psi isn't any different than a sherman short case running @ 72K, which I'm sure plenty do with the velocity they get. I doubt barrel wear will be any worse than a 270wsm.

There are some cartridges that are more efficient like the Sherman short mag and other wildcat designs that help handle the pressure better and control the side effects from pressure. but the difference in 70,000+ Psi and 80,000 Psi is not comparable. There are things that can be done to improve a cartridge enough to out perform other more powerful cartridges with a lot less powder and therefore not require more pressure.

Pressure and temperature do the most damage in the 3,000+ ft/sec cartridges. I don't know what Psi the SS mags run, but I would think that around 65,000 Psi would be all that's needed. One of my wildcat designs, will push a 300 grain 338 bullet over 3150 ft/sec without trashing the case and hurting the action because of the design. And when backed off to 3,050, it doesn't show any signs of pressure operating at 62,500 psi.

Better design, less powder = less pressure needed to get the same velocity.

J E CUSTOM