.264 USA (spin-off from FBI Selection Process thread)

[MistWolf]

...Or were you talking about one of the other cartridges that I could google for you?

Yes, I was talking about the .264 USA. It helps, when talking about a new or uncommon cartridge, to include basic data so that we know what we're talking about. It helps the flow of the technical aspect of the conversation to not have to search for basic information. Based on the above, it looks like the USA is nearly the ballistic twin of the Grendel. Without comparing actual data, the thread feels like we're talking about his round because it's new & shiny rather than because it offers any kind of performance advantage

[DocGKR]

Mistwolf--6.5G and .264 USA are NOT ballistic twins.

Just look at capacity for propellant of some common cases:

.300 BLK = 18.4 gr
5.56 mm NATO = 27.3 gr
7.62x39 mm = 28.8 gr
6.8 SPC = 30.9 gr
6.5G = 31.5 gr
.264 USA = 40.0 gr
6.5x47 = 43.6 gr
7.62 NATO = 48.2 gr
.260 Rem = 49.5 gr
.30-06 = 57.0 gr
.300 WM = 84.8 gr

.264 USA offers quite a bit more options than 6.5G or other short action cartridges...

[SecondsCount]

Mistwolf--6.5G and .264 USA are NOT ballistic twins.

Just look at capacity for propellant of some common cases:

.300 BLK = 18.4 gr
5.56 mm NATO = 27.3 gr
7.62x39 mm = 28.8 gr
6.8 SPC = 30.9 gr
6.5G = 31.5 gr
.264 USA = 40.0 gr
6.5x47 = 43.6 gr
7.62 NATO = 48.2 gr
.260 Rem = 49.5 gr
.30-06 = 57.0 gr
.300 WM = 84.8 gr

.264 USA offers quite a bit more options than 6.5G or other short action cartridges...

I can see the case capacity differences but what has me confused is the 264 USA has a listed muzzle velocity(MV) of 2657 FPS while the 6.5G shows 2650 FPS. Those are very similar ballistics.

Bump that 264 USA up to 2900 FPS with a 123 and then I would be interested but they call that the 6.5x47

[TiroFijo]

You have to compare both calibers with the same barrel length...

The 264 USA should be about 200 fps faster than the the 6.5G with 123 gr bullets out of 16"-18" barrels.

Remember this is stil the search of the "just right" Goldilocks round. If you want more velocity, you are into full power cartridge area, with better ballistics and range (260/6.5x47/6.5 Creedmore) but more recoil, reduced performance and more blast in short barrels, and larger size and weight of the round.

[SecondsCount]

You have to compare both calibers with the same barrel length...

The 264 USA should be about 200 fps faster than the the 6.5G with 123 gr bullets out of 16"-18" barrels.

Remember this is stil the search of the "just right" Goldilocks round. If you want more velocity, you are into full power cartridge area, with better ballistics and range (260/6.5x47/6.5 Creedmore) but more recoil, reduced performance and more blast in short barrels, and larger size and weight of the round.

One would assume the velocity would be higher but not always. It depends on the efficiency of the case design and the pressures and powder.

I would be interested in what they could do in 6mm with a bullet BC in the high .300's. I have a friend that has a 14" Thomson contender in 6x45 and am impressed by that caliber. I think the velocity is too slow for .mil purposes but with a little bit larger case it would make for an interesting test.

[TiroFijo]

One would assume the velocity would be higher but not always. It depends on the efficiency of the case design and the pressures and powder

My comments were based on published/released data for both rounds...

[bfoosh006]

Caseless ammo is a dead end, from the HK employee that was in charge of the G11.

The future, IF it ever comes, is lightweight cases of some sort. And the new generation rifles/MG and new round (with ballistics and caliber yet to be decided) are waiting for it, so the transition will truly be worth the effort.

My bad it is 6.5 Cased Telescoped ammo....

http://www.dtic.mil/ndia/2016armamen...5_Phillips.pdf