Quoted: What is curious is the choice to use a gas piston on an "urban sniper" rifle?

I guess they never talked to anyone who built Match M1A/M14s. Maybe someone has figured out what folks like John Miller couldn't when dealing with a piston slapping around on a barrel.

Quoted: Quoted:  What is curious is the choice to use a gas piston on an "urban sniper" rifle? I know that the developmental (military) 7.62 rifles for the urban shooters use the DI system... but they are going for the best accuracy they can get. I guess it's been said before, but there certainly are ways to get the same or better accuracy out of rifles with gas pistons.

I'll have to introduce you to some of the old National Guard Armorers, and you can talk to them about building Match M14s vs. Match ARs.  All things equal, the gas piston will never be as accurate as DI.

I shoot higher Long Range scores with my M1A than I do with my AR. But thats because of the ergonomics(talking about slung up prone), and the sight radius. I know my M1A is not as accurate as my AR.

Quoted: If this .308 piston system proves to be able to put up .5 MOA groups will we stop the "gas pistons cant be accurate" the way we have stopped with the 5.56 gas piston version or will we continue to berate the gas piston as useless because it wont do sub 2" groups at 300 yards?

The gas piston is not useless by any means. The FAL is an excellent rifle.  There's a reason, after all the years of development and research, the "precision" autoloaders in the field today are DI.

Quoted: I just do not understand for the life of me how people can claim a DI gun does not apply a bending moment to the bbl.  NO PERSONAL ATTACK INTENDED WHAT SO EVER!  But It does!  So does a gas piston system!

My two cents...

Matt is correct.
Both systems apply SOME force to the gas block.
The difference is that the gas force acting to pust against the FSB on a DI gun is limited by the inside diameter of the gas tube.

Let's take a simple example.
Assumptions for the example, even if they are not true numbers, but just for arguement's sake:
We will assume for simplicity that a piston driven system pushes against the bolt carrier to function the gun.
We will also assume that the other end of the piston is mounted to the FSB.
For the DI example, we will assume that the gas expanding inside the carrier is acting against the bolt and against the carrier.
As the bolt is pushing against the cartridge case and the end of the barrel, the carrier will be the only part to take the energy of gas expansion.
Our port pressure will be 10,000 PSI because it's a nice round number, not because it's correct.
Our gas tube will measure 0.125" inside diameter.
Our gas piston and bore are right about 0.375".

The actual assumed numbers used don't matter except to the extent that pistons MUST be bigger in diameter than gas tubes in order to work from the same gas pressure provided at the port.
So, put 10,000 PSI into the gas tube and it would PUSH against the FSB with 122lbs of force.
In case you are not aware, PSI is Pounds per Square Inch.
0.125" gas tube diameter is 0.012265625 square inches of area.
The math is simple, 10,000 PSI x 0.012265625 square inches is roughly 122lbs give or take 1/4 lb.
That same 10,000 PSI port pressure would create 1104 lbs of PUSH on the FSB with a 0.375' diameter piston system.
0.375" diameter piston is 0.110390625 square inches of area.
Again, the math is simple, 10,000 PSI x 0.110390625 square inches is roughly 1104lbs give or take 0.004 lbs.

From my simple example, we see a 10X factor of thrust on the FSB.
Is this a possible cause of vertical stringing as the barrel's properties change?
I would tend to think so.
Maybe Matt can tell us the ACTUAL numbers such as piston diameter, gas tube diameter and port pressure so that any of us here can run the numbers ourselves.
That should put the whole FSB thrust issue to bed.
As for me, it's 1:26am, so I am also going to bed.

Quoted: Yes.  The expansion chamber on a DI gun is presurized vs. a piston.  The expansion chamber is a piston, we should note. Ok, so, that is presurized.  But, just because the expansion occures at a location behind and inline with the bbl does not mean you get to discount all the intermidate bits.  Look at these pictures.  Would A cause a moment on the bbl?  Would B?  Would C?  Would D?

The key difference the DI guys are arguing is that the piston in the DI gun is captured against the breech end of the gun, well inside the reciever so the forces of the gas expansion (D) are NOT transmitted to the FSB beyond what you can get from the gas tube bore.
Because the Piston driven system pushes directly against the FSB, the forces are much higher.

I'm one of those midnight theoriticians, don't take my posts as coming out against the gas piston system.
I think it's many merits probably outweigh it's disadvantages.
If I could buy component systems, I could start putting these on some 300x221 barrels that would REALLY benefit from the extra force of a short gas path to a piston near the FSB.
It's really hard to make a DI action run on only 10,000 PSI of port pressure with a 5" long gas path to the carrier.
Thank goodness for the dwell time of subsonic 240's

And I will see ya all at the Shoot on Saturday as I am supposed to be on the list.
I have the time schedule.
If someone could just email me the address of the range it would be helpful.
I suppose a call to the dept may answer my question as well though.

Quoted: First off, if you don't know how their piston system actually works, don't comment on it.

Whose comment is this pointed at?

Quoted: BigBore.  Please come to the shoot at shot.  Also, give John Noveske a call and ask him what he found with the system .

I'm not going to make it out there this year.  Luckily, I frequent the range where precision equipment is proven or dismissed.  If these uppers as as accurate as DI, I'm sure I'll be seeing them in the near future being put to the test, by good shooters with recorded results.