Sniper & Sharpshooter Forums banner

1 - 10 of 10 Posts

·
Registered
Joined
·
94 Posts
Discussion Starter · #1 ·
Why not neck down a 50 bmg case to seat a .408 Cheytac bullet, I know you'll say we already have the Cheytac and the .416 Barrett so why create yet another ultra long range cartridge?, I would say to save flight time and to give the 419 grains bullet a flatter flight path , so did anybody you know of neck down a 50 BMG case without shortening it like the case with the .416 Barrett, I think this should add considerable muzzle velocity to the 10.3mm bullet which would enhance it's reach and accuracy considerably, what do you think?
 

·
Registered
Joined
·
308 Posts
necking down 50

wow what a thumper,do it and find out.in my opinion the barrel life would be short with all the fire and hot gas coming out a smaller hole would eat the throat out faster than normal,being around a friend that owns a smithing shop he is seeing it already in the short mag, super short mag calibers with the short fat cases with smaller projectiles that the major players touted up in the past few years there are some articles out there on the subject it is called over bore if i remember correctly.good luck with it
 

·
Registered
Joined
·
198 Posts
Have you given any consideration to using a sabbot? They've been using .308 to .223 sabbots with much success, I would think the out come would be the same without the throat erosion issues.
 

·
Registered
Joined
·
1,797 Posts
With every bore size, there is such a thing as bore capacity. The .50 Browning case probably holds too much powder for a .408 bore.

You could probably shorten the .50 Browning case and come up with a real humdinger .408 cartridge.

Examples of overbore cartridge cases: .257 Weatherby and .264 Winchester Magnum:

Examples of efficient cases that operate at bore capacity: .257 Roberts and 6.5x55mm.

If you compare say the .257 Roberts with the .257 Weatherby, you will see that it takes lots and lots of extra powder to produce a few hundred additional feet per second velocity. The same is true when you compare the 6.5x55mm with the .264 Winchester. The law of diminishing returns applies to both examples in spades. And all that extra powder diminishes the barrel life.

With the .257 Roberts, a 120 grain bullet can be launched at 2800 fps using 45.0 grains of IMR-4831.

With the .257 Weatherby a 120 grain bullet reaches 3200 fps when fuelled by 65.0 grains of IMR-4831.

It takes 20 grains of powder to gain 500 fps of velocity. You gain only 25 fps of muzzle velocity for every additional grain of powder. That's pretty inefficient as I see it.

With the 6.5x55mm, a 120 grain bullet fuelled by 49.0 grains of IMR-4831 reaches 2886 fps.

With the .264 Winchester, a 120 grain bullet fed by 59.0 grains of IMR-4831 reaches 3082 fps.

With the .264 Winchester it takes 10 extra grains of powder to gain 200 fps muzzle velocity. At 20 addition feet per second per additional grain of powder, that's even more inefficient than the .257 Weatherby.

A .408 case based upon a full sized .50 Browning would probably be a very inefficient round. But a shorten .50 Browning case, would be an interesting proposition.

Finally, to fans of the .264 Winchester and .257 Weatherby, please don't get angry. I like both rounds as hunting rounds. They both have specialized uses.


Mad
 

·
Registered
Joined
·
4,795 Posts
Hey, better yet neck down a 20 mm roung to 6.5 :D
 

·
Registered
Joined
·
198 Posts
:shock: ekaphoto, isn't that kind of like launching a .22 60gr. from an Abrams :lol: ?
 

·
Registered
Joined
·
94 Posts
Discussion Starter · #9 ·
I'm a reluctant to consider sabots as for an ultra long range cartridge they degrade the accuaracy of the cartridge quite a bit, and I think that probably the .416 Barrett and the .408 Cheytac are built that way for a reason :)

I thank you all for your opinions and would like to give special thanks to Madgunsmith for talking to us about the "law of diminishing returns and efficient cartridges".
 

·
Registered
Joined
·
3 Posts
I'm a reluctant to consider sabots as for an ultra long range cartridge they degrade the accuaracy of the cartridge quite a bit, and I think that probably the .416 Barrett and the .408 Cheytac are built that way for a reason :)

I thank you all for your opinions and would like to give special thanks to Madgunsmith for talking to us about the "law of diminishing returns and efficient cartridges".
Everyone keeps trying to figure out how to use a 50 BMG case with 408 or 375 . The 50 ,460 and the 416 all use simler case .until now those have been the starting platforms neck up or down can’t quite make the 375 work without being way over bore. Enter a new cartridge based on 50 BMG but designed and engineered to maximize proformance of the 375 bullets . With the right velocity to be effective at ULR . Made in US super long life brass you should check this new cartridge out at missionshootingsupplies.com
 
1 - 10 of 10 Posts
Top