338 sherman

[horslips]

anybody have experience with the 338 sherman

 

[CjC73]

a little... what's your question

 

[horslips]

everything , reloading, ballistics

 

[CjC73]

to start....

https://shermanwildcatcartridges.com/338-sherman

It's a long action with standard bolt face. Based off the 270Win case. Neck it up to 338 cal and fireform by jamming the bullet way into the land to create a seal. Once formed, you can start load developing and setting the bullet off the lands. I'll post a picture of a pre-formed case with it after fire formed.

Ballistics. Depends on how much you want to push max pressure and velocity. But reports of pushing a 250 grain Berger Hunter upwards of 2900fps are out there, that's over 4400 ft-lbs of muzzle energy. I'm about to load up some for hunting next week but I'll load it down some, my shots are not that long. But probably go with a 225 grain and 2500fps. Still get over 3000 ft-lbs of muzzle energy. more than enough for a whitetail.

 

[CjC73]

270win necked up ready to be fire formed on the left
A formed 338 Sherman brass on the right

 

[wboggs]

I am curious about the reports of 2900 fps with a 250gr. bullet. Any reference on this?

 

[horslips]

thanks for the info

 

[CjC73]

read the info in the link. and there is reloading data showing the same. velocities between 2800 and 2900 fps.

 

[wboggs]

Thanks.

 

[762 ULTRAMAGA]

I would be very cautious in what you're reading about some of the Sherman velocities, 2900 with 250s is 338 RUM territory.
I know a few guys who've built 7 Sherman's, and they had loose primer pockets after a few firings with ADG brass chasing those claimed numbers

 

[wboggs]

Please keep us informed of your loading results. Do you plan on loading anything heavier than 225 gr? What is the throat length on your rifle? This type case modification is similar to old Gibbs series.
It will be interesting to see how it does with modern powders.

 

[CjC73]

Yes. Sharper shoulder and pushed forward. Body taper is almost gone. maximize the volume.

 

[B23]

I would be very cautious in what you're reading about some of the Sherman velocities, 2900 with 250s is 338 RUM territory.
I know a few guys who've built 7 Sherman's, and they had loose primer pockets after a few firings with ADG brass chasing those claimed numbers

The case capacity just doesn't support anywhere near those kinds of velocities so if they're getting there it's being done at some pretty crazy pressures.

When you square the shoulder off like that and take all the taper out of the case it does a pretty good job of hiding some of the standard pressure signs and people tend to get velocity drunk when they don't see flat primers or ejector marks and just keep pouring more powder in the case.

 

[David Milisock]

You guys are going wher we went with the 358 Norma years ago.

 

[CjC73]

The case capacity just doesn't support anywhere near those kinds of velocities so if they're getting there it's being done at some pretty crazy pressures.

When you square the shoulder off like that and take all the taper out of the case it does a pretty good job of hiding some of the standard pressure signs and people tend to get velocity drunk when they don't see flat primers or ejector marks and just keep pouring more powder in the case.

I'm not claiming to know all the physics/thermodynamics/etc. behind it but there's a lot of rifles out there shooting those velocities with no issues so apparently it does support it. They work up to the max load just like any reloader does, looking for ejector marks or flat primers.

 

[B23]

That's just it, the physics does not support it. You can't take a case with substantially less case capacity and get magical velocities that equal or even supersede those with much larger case capacity without doing it with extreme pressure.

If they choose to run their stuff at extreme pressure to get whatever velocity they want makes no difference to me just don't pretend like your getting those velocities without it.

 

[CjC73]

I never said anything about pressures. And if the action is capable, what does it matter? that case is providing the capacity and efficiency to push those velocities as noted from numerous shooters.

 

[David Milisock]

That's just it, the physics does not support it. You can't take a case with substantially less case capacity and get magical velocities that equal or even supersede those with much larger case capacity without doing it with extreme pressure.

If they choose to run their stuff at extreme pressure to get whatever velocity they want makes no difference to me just don't pretend like your getting those velocities without it.

There is no free lunch. The (I hate the term magnum) enhanced performance cartridges gets that performance with one major component and that is pressure.

With that said there is also freebore, powder pressure curve and barrel length elements in that equation.

My experience is with the 358 Norma (similar case volume and standard action concept), I get 3,200 FPS with 250 grain Hornady SP. The barrel was custom cut, the barrel is 30" and the powder researched and different loads worked for 18 months. The case is a 64,000 PSI concept. I had a guy lose a steak dinner on a bet that I didn't get 3,200 FPS, it's just the perfect combination, the bolt opens with my pinky finger with no marks on the brass just a flat primer. Cases have over 10 loads with no problems.

The results of having similar velocities in the smaller a case as a larger case volume usually work for only one bullet weight. An example is my 358 Norma, it matches or exceeds 358 STA velocities with the 250, falls behind with 300's or heavier.

I also see similar capabilities with the short fat cases, they do well against their long narrow case counterparts with some projectiles. Example 300 mag and the various short mag versions.

 

[762 ULTRAMAGA]

I never said anything about pressures. And if the action is capable, what does it matter? that case is providing the capacity and efficiency to push those velocities as noted from numerous shooters.

I owned a 30 SM and I can tell you for a fact the numbers people were posting are dangerous.
I didn't get ejector marks and kept going until my bolt was slightly stiff, well those cases were trashed after that and I still didn't even get to 30 Nos velocities let alone RUM velocities that we're being claimed.
I'd like to know the case capacity of the 338 Sherman, my 338 RUM was around 106 grains and hit pressure around 2950 with 250 Bergers.
My 338 NM hit pressure just under that, and it held around 104 grains with lapua brass.

Sherman cases are pretty cool but we have to understand that there really isn't any magic going on, just extreme pressures

 

[David Milisock]

I owned a 30 SM and I can tell you for a fact the numbers people were posting are dangerous.
I didn't get ejector marks and kept going until my bolt was slightly stiff, well those cases were trashed after that and I still didn't even get to 30 Nos velocities let alone RUM velocities that we're being claimed.
I'd like to know the case capacity of the 338 Sherman, my 338 RUM was around 106 grains and hit pressure around 2950 with 250 Bergers.
My 338 NM hit pressure just under that, and it held around 104 grains with lapua brass.

Sherman cases are pretty cool but we have to understand that there really isn't any magic going on, just extreme

There is no magic! This thread is interesting so I went looking and finding all the pertinent information is impossible let alone finding it all in one place.

I'm interested in all the details, case capacity, custom cut chamber, barrel length, powder and bullet weight.

There's no doubt that the shorter, fat powder column has specific efficiencies. Look at the 6MM ARC in a 24" barrel with a 108 grain projectile and the small amount of powder to get 2,750 FPS. However go to 110 + grain and start pushing the pressures and you'll separate the wheat from the chafe.

I can't see the physics being any different, for the Sherman. With equal barrel length I can see 1 projectile weight being competitive in the Sherman but I'd like to see the specs if that is the 250 grain. If I did the Sherman I'd give it more tube.