Thread: Pushing 308 to 300WM speeds.

there is/was a new type of case being bandied around about a year ago..special forces round in 6.8mm ??? has steel head and brass body to withstand much higher pressure than normal. the technology is there to do the high pressure thing,Ive always thought a thick walled case was a feasable idea,sort of take the belt on likes of 7mm magnum all the way from head to shoulder to enclose the bit that stretches /gives out.

Originally Posted by Micky Duck

there is/was a new type of case being bandied around about a year ago..special forces round in 6.8mm ??? has steel head and brass body to withstand much higher pressure than normal. the technology is there to do the high pressure thing,Ive always thought a thick walled case was a feasable idea,sort of take the belt on likes of 7mm magnum all the way from head to shoulder to enclose the bit that stretches /gives out.

Greetings,
It was introduced as the 6.8 or .270 Fury as a military and later commercial cartridge. About the size of a 7mm-08 but with .270 Win or better performance. The steel head cases came out in the US about 50 years ago.
GPM.

@grandpamac

Have a look at gordons reloading tool, if you are missing quickload. Its a free (and better!) alternative

So..,steel cases,like what Barnaul etc use,how do they stack up as a single use item,as so far as handling excess pressure??

Yrs ago i was in a shooting compitition,north canterbury.We started at 100yds to make sure our rifles were on song.Guy 2 mtrs along from me had a 270 with some new reloads he was trying out.His second shot gave a loud explosive bang,his head flew back about 1/2 a metre,blood and smoke off his face.The bolt was blowen back with bits missing,scope had a few marks on it.Lucky he was wearing shooing glassess.Officials came running over to him,with 1st aid.Rifle was buggered for a while but he keeped his eye sight.

Originally Posted by Trout

Yrs ago i was in a shooting compitition,north canterbury.We started at 100yds to make sure our rifles were on song.Guy 2 mtrs along from me had a 270 with some new reloads he was trying out.His second shot gave a loud explosive bang,his head flew back about 1/2 a metre,blood and smoke off his face.The bolt was blowen back with bits missing,scope had a few marks on it.Lucky he was wearing shooing glassess.Officials came running over to him,with 1st aid.Rifle was buggered for a while but he keeped his eye sight.

A extra fps just ain't worth it

Yes SIG have released the 277 fury rifle and cartridge. It has been SAAMI spec'd at 80,000psi,
Yes it is a composit case, steel & brass with alloy as well.

QL pressure I take is an estimated pressure from the Quick Load tables.
How were they getting the corrected pressure number?

Originally Posted by Lauries Hut

QL pressure I take is an estimated pressure from the Quick Load tables.
How were they getting the corrected pressure number?

Think they were using the QL velocity vs actual velocity and taking that percentage difference and applying it to the QL pressure estimate.

Originally Posted by Lauries Hut

QL pressure I take is an estimated pressure from the Quick Load tables.
How were they getting the corrected pressure number?

Greetings @Lauries Hut,
The relationship between velocity and pressure is quite linear as it is between powder charge (for the same powder) and velocity. This can be demonstrated with the Hodgdon load tables and a pocket calculator or a graph. I use the same methods but I am looking for a safe load at less than maximum pressure where the vid was demonstrating the fallacy of working up using pressure signs. For many cartridges the book data is right on the button once barrel length has been factored in. Some powders and some projectiles give quite different results due to a change in powder speed or projectile construction. I differ from some in I prefer to base loads on published and pressure tested data rather than Quickload which is an estimate based on case capacity. Correcting a velocity based on an estimate is still an estimate.
Regards Grandpamac.

+1 for Gordons Reloading tool. I’m trying to work up a 308 load which has no book value for, and I’ve used it for a baseline to understand pressures and where to find the limit. Ironically my real life chronograph figures are lower than predicted from the application, but it still a good place to be to understand where to stop. (Currently sending a 185gr D46 @ 2750fps)

I’d watched the UR video and did wonder how many people would replicate it without the basic understandings. I cringe when I talk to some handloaders that just load based on the group on target at 50-100M, without measuring speed or looking up pressure max.

I thought it was a stupid video, and only told everyone hat they already knew. That 308 was 300-400fps slower than 300wm unless you make a dangerously high pressure load.

I thought perhaps they were going to try RL17 or Rl26 or some other exocitic(ish) powder to try squeeze maximum performance form the 308 case.
But once I saw they were using Varget I skipped to the end as I knew what the conclusion was going to be.