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Posted: 2/7/2006 12:57:58 PM EDT
Leitner-Wise/Grenadier Precision 308 semi auto urban sniper - piston driven.


Link Posted: 2/7/2006 1:02:32 PM EDT
That's sweet. What sort of groups are you getting with that setup?
Link Posted: 2/7/2006 1:57:32 PM EDT
That's pretty cool.

WIZZO
Link Posted: 2/7/2006 2:17:02 PM EDT
Sweet
Link Posted: 2/7/2006 2:18:28 PM EDT
is that based on the DPMS rifle it look so.
Link Posted: 2/7/2006 2:20:13 PM EDT
[Last Edit: 2/7/2006 2:53:22 PM EDT by DevL]
So will they be doing DPMS only? Is it carbine length gas port location? Also will there be a .308 GP rail system?
Link Posted: 2/7/2006 2:51:22 PM EDT
Tag for more info.
Link Posted: 2/7/2006 2:55:31 PM EDT


I'm not diggign the SIR, but I do understand why (I think), as it is one of the systems that the LW piston will fit under.

I love the .308 AR platform and my AR-10, even took it deer hunting this year (no killing, just humped it through the woods on a couple of hunts).
Link Posted: 2/7/2006 3:21:22 PM EDT
cool,

whats the accuracy out of it, Custom barrel?
DPMS only or can it be done to an armalite


Link Posted: 2/7/2006 4:38:48 PM EDT

Originally Posted By mongo001:


I'm not diggign the SIR, but I do understand why (I think), as it is one of the systems that the LW piston will fit under.

I love the .308 AR platform and my AR-10, even took it deer hunting this year (no killing, just humped it through the woods on a couple of hunts).



That is sort of a drag really, the limited handguard systems that will work with that gas system.

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.
Link Posted: 2/7/2006 4:42:16 PM EDT
Please don't take this offensively, BUT IT'S ABOUT DAMN TIME!



Excellent! Keep up the good work guys.
Link Posted: 2/7/2006 4:44:45 PM EDT
Is that the new SIR fore-end?


Cheers
Link Posted: 2/7/2006 4:46:16 PM EDT
Looks Expensive!hock.gif Really EXPENSIVE
Link Posted: 2/7/2006 4:57:00 PM EDT
Tag.

Looks like the regular ARMS forend, AR10 model, rifle length.

I want to see the barrel end up close.
Link Posted: 2/7/2006 5:00:18 PM EDT
Link Posted: 2/7/2006 5:11:00 PM EDT
Does ARMS make an .308-specific SIR? Looks like it goes all the way back on the top receiver rail like on a 5.56 AR with no gap before the rear sight.

Gas piston reliability, 7.62 ballistics and AR ergonomics sounds like a winning package.

Link Posted: 2/7/2006 6:03:02 PM EDT
[Last Edit: 2/7/2006 6:05:53 PM EDT by SWO_daddy]
Call me old fashioned, but I'd rather have this:


Or this:
Link Posted: 2/7/2006 6:15:24 PM EDT
[Last Edit: 2/7/2006 6:16:07 PM EDT by ian187]

Originally Posted By bigbore:

Originally Posted By Gunzilla:
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.



This not the time or the place for common sense.

Link Posted: 2/7/2006 6:18:50 PM EDT

Originally Posted By Gunzilla: 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.
Link Posted: 2/7/2006 6:29:25 PM EDT
[Last Edit: 2/7/2006 6:38:16 PM EDT by bigbore]
Link Posted: 2/7/2006 6:38:47 PM EDT
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?
Link Posted: 2/7/2006 6:43:15 PM EDT
Link Posted: 2/7/2006 6:52:06 PM EDT

Originally Posted By bigbore:

Originally Posted By SWO_daddy:

Originally Posted By Gunzilla: 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.


Meet Clint Fowler

Meet his rifles

There are several reasons why the AR is so intrinsicaly accurate. The bedding (or lack of it) is one major one. But there are ways to compensate, even with the old warhorses of iron and wood.
Link Posted: 2/7/2006 6:56:49 PM EDT
Because they are based on the AR DI platform... no bedding required, propper optics mounting location, etc. Its more thn just the gas system.

I wonder how the SCAR-H will work, and time will tell, but if the LW 5.56 is as accurate as the DI version I dont see why the LW system on a .308 will be any less accurate either.
Link Posted: 2/7/2006 7:24:14 PM EDT
The biggest problem with a piston system is the vertical stringing of shot placement after the barrel warms up. Cold barrels are stout and rigid. A piston system on a AR action will produce a tight group (.500 MOA) on a cold barrel. After a volley of 60 plus rounds, the group size through vertical stringing will increase as much as 1.5 MOA. Crappy!

A .308 with a DI system keeps its accuracy, even after the barrel gets hot (rapid fire 60 rounds plus). The only noticable difference is with the a group placement with a hot bore. I've seen as much as 3/4 MOA drop, but when the barrel cools, the group returns to it's "cold" placement. Cold or hot, the group size barely changes.

If I wanted a .308 rifle with a piston, I would a SIG 540 or a Galil. A .308 DI rifle is made for accuracy.

wp
Link Posted: 2/7/2006 7:25:25 PM EDT
In 5.56mm and 6.8mm our systems did not show worse accuracy than DI guns in the same caliber, bbl length, and ammo catagories. I do not know what a match LW would do compared to a match DI cause all I have ever shot is standard ammo in standard guns.
Link Posted: 2/7/2006 7:33:51 PM EDT

Originally Posted By Wackypeacock:
The biggest problem with a piston system is the vertical stringing of shot placement after the barrel warms up. Cold barrels are stout and rigid. A piston system on a AR action will produce a tight group (.500 MOA) on a cold barrel. After a volley of 60 plus rounds, the group size through vertical stringing will increase as much as 1.5 MOA. Crappy!

A .308 with a DI system keeps its accuracy, even after the barrel gets hot (rapid fire 60 rounds plus). The only noticable difference is with the a group placement with a hot bore. I've seen as much as 3/4 MOA drop, but when the barrel cools, the group returns to it's "cold" placement. Cold or hot, the group size barely changes.

If I wanted a .308 rifle with a piston, I would a SIG 540 or a Galil. A .308 DI rifle is made for accuracy.

wp



You are saying this is caused by forward pressure of the return spring on the front sight base after the barrel is warm and it causes the barrel to bend downward?
Link Posted: 2/7/2006 7:51:00 PM EDT
No, it's more like the following:

The gas pressure against the piston face needs to go somewhere. Normally, the piston moves and the rest is history, but not when the barrel gets hot. When the barrel gets hot, it gets soft and flexible. So when the barrel gets hot, it wants to move away from the piston, by flexing away from the piston. This leads to what is called Vertical stringing.

HK learned the hard way, that's why the 416 has such a stout and heavy barrel, to lessen the vertical stringing. Unfortunately, by making the barrel thicker, they added a pound plus in its overall weight. Stoner, the French and the Swedes did their home work. Why re-invent the wheel.

wp
Link Posted: 2/7/2006 8:17:07 PM EDT

Originally Posted By JIM762:
Looks Expensive! Really EXPENSIVE



You forgot HEAVY!
Link Posted: 2/7/2006 8:58:35 PM EDT
So the gas inside the gas tube of a DI gun exerts no pressure on the FSB?

Not to be a smart ass, but for the gun to work there needs to be pressure in the gas tube, and if there is pressure in the gas tube, there is a moment on the bbl.
Link Posted: 2/7/2006 9:11:10 PM EDT
[Last Edit: 2/7/2006 9:12:34 PM EDT by ian187]

Originally Posted By LWRC_Matt:
So the gas inside the gas tube of a DI gun exerts no pressure on the FSB?

Not to be a smart ass, but for the gun to work there needs to be pressure in the gas tube, and if there is pressure in the gas tube, there is a moment on the bbl.



The gas tube flexes where as the piston does not. The piston acts directly on the barrel, the gas tube does not.

Link Posted: 2/7/2006 9:18:15 PM EDT
And why does it flex? Cause it is anchored at one end. That end is applying force. If it was not, the tube would not flex. So, since that end (fsb) is applying a force, a force acts equally on it.

And both connect to the fsb. neither to the bbl direcly.
Link Posted: 2/7/2006 9:22:48 PM EDT
[Last Edit: 2/7/2006 9:27:08 PM EDT by ian187]

Originally Posted By LWRC_Matt:
And why does it flex? Cause it is anchored at one end. That end is applying force. If it was not, the tube would not flex. So, since that end (fsb) is applying a force, a force acts equally on it.

And both connect to the fsb. neither to the bbl direcly.



If the tube flexes the forces is not equally applied because the tube itself is absorbing energy.

ETA: I see where this is going so if you would like to prove this wrong post some highspeed film to prove your position. The DI system is long proven to work exactly as I described.

Link Posted: 2/7/2006 9:40:50 PM EDT
Id be more interested in a video of 2 20 round mag dumps followed by 4 5 shot groups for accuracy at 100 yards. If it works, it works and it dooes not matter what the technical reasons are or are not.
Link Posted: 2/7/2006 9:52:30 PM EDT
Yes some energy is absorbed. I never said the tube does not flex. I agreed that it does. Let me put it this way: if you can draw me a free body diagram of the bbl where there is no force acting on the bbl at the location of the gas block and there is no moment applied to the bbl I will have 20 dollars in the mail to you asap.

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!


And, I can say that while, as I said, I have never tested a match grade LW, my 100 yard groups with a particular weapon were just over an inch using factory 6.8 ammo which i know from chrono to be inconsitent. I have never seen a patern like the vertical stringing some describe. The groups are just as randomized as any I have seen. (6.8mm 16" m4 profile, Rock River 2 stage, free floated, shooting on my stomach, forget who made the glass on that gun.)

And, I agree with DevL.
Link Posted: 2/7/2006 10:08:47 PM EDT

Originally Posted By LWRC_Matt:


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!





Because the expansion chamber in a DI AR15 is the bolt and carrier where as a piston upper has the expansion chamber attached to the front sight base. The DI bleeds pressure off through carrier which eliminates the downward pressure seen in a piston system. Instead of pushing forward and down on the end of the barrel the pressure pushes the bolt and carrier apart directly in line with the axis of the bore. The gas tube flexes also because the barrel flexes when the rifle is fired.

Link Posted: 2/7/2006 10:26:27 PM EDT
Nice....anyone know what the going price will be?

Link Posted: 2/7/2006 10:37:08 PM EDT
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?



I dunno maybe I am having a hard time explaining myself. You totally disagree with me and that is fine.
Link Posted: 2/7/2006 10:48:22 PM EDT
These were 2 proof of concept guns. They shoot very nicely. No pricing yet obviously as the whole thing needs to be productionized if there is such a word.

I don't care to debate with people over the theorists and their piston theories. You are applying apples to oranges comparisons. What could be considered the piston is fixed to the gas block (NOZZLE), the lightweight cup or cylinder is what reciprocates. A whole .6" and is venting subsonic gas the whole time in all directions equally and is a staged vent back and forth. The cup does not even push off until the bullet has left the bore.

2 types of people in this world. Those who have experience with what they say and those who spend hours theorizing without any first hand knowledge. The world is flat.

Feel free to attend a demo shoot and see how your theories apply.

BigBore. Please come to the shoot at shot. Also, give John Noveske a call and ask him what he found with the system .
Link Posted: 2/7/2006 11:48:39 PM EDT

Originally Posted By Gunzilla:


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 must be missing something. Should it be instead labeled a "rural sniper rifle"?
Link Posted: 2/8/2006 12:26:41 AM EDT
Link Posted: 2/8/2006 12:44:37 AM EDT
Link Posted: 2/8/2006 1:09:32 AM EDT
[Last Edit: 2/8/2006 1:10:34 AM EDT by Variablebinary]
.5 MOA vs 1 MOA, Piston vs DI

Here is the answer as to which is better. Which system doesnt have carbon building up on the guts of the gun after every shot

That's the better system


I'm a lazy bastard and hate cleaning my AR15 for 30 minutes after a day at the range

BTW, cool gun LW. Very nice effort
Link Posted: 2/8/2006 2:53:41 AM EDT

Originally Posted By Variablebinary:
.5 MOA vs 1 MOA, Piston vs DI

Here is the answer as to which is better. Which system doesnt have carbon building up on the guts of the gun after every shot

That's the better system


I'm a lazy bastard and hate cleaning my AR15 for 30 minutes after a day at the range

BTW, cool gun LW. Very nice effort



Well, that the difference between a precision sniper rifle and a main battle rifle. The difference between the two definitions is about 1.5 MOA.


Hey Mr. AR Barrels,

Well put! I have seen high speed video of a DI in action. The video was taken with an A1 rifle the handguards removed. What is most noticeable is how much energy is dissipated through the slight goose neck formed in all gas tubes. Stainless steel is an excellent material for memory and tensile strength, just don't get it too hot.

wp


Link Posted: 2/8/2006 4:30:17 AM EDT
Anything better than MOA is gravy in a sniper rifle. Take that weapon off the bench and very few marksman can hold MOA in all the basic shooting positions both suppoted and unsupported. If you can than your a better sniper than me. I like the piston systems. I'm excited to see whats nexted. I see they beat POF to the 308.
Link Posted: 2/8/2006 5:06:37 AM EDT

Originally Posted By 48thHighlander:
These were 2 proof of concept guns. They shoot very nicely. No pricing yet obviously as the whole thing needs to be productionized if there is such a word.

I don't care to debate with people over the theorists and their piston theories. You are applying apples to oranges comparisons. What could be considered the piston is fixed to the gas block (NOZZLE), the lightweight cup or cylinder is what reciprocates. A whole .6" and is venting subsonic gas the whole time in all directions equally and is a staged vent back and forth. The cup does not even push off until the bullet has left the bore.

2 types of people in this world. Those who have experience with what they say and those who spend hours theorizing without any first hand knowledge. The world is flat.

Feel free to attend a demo shoot and see how your theories apply.

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



Well said! I had agreed in IM to keep my mouth shut on this thread... but had to give my support to this. Gas Pistons are by no means new, they in fact are older than the DI design and the AR platform has been available with a gas piston for over thirty years now -- All of this has been tested and played out time and time again by people in actual real world testing!

Gas piston systems can be very accurate, but they have proven to not be as accurate or first shot predicatble as the DI system... I too have seen all of this is high speed video, test guns build with plastic barrels that used compressed gas to cycles that action, range testing and real life use. I am a big fan of the gas piston in places where it is the best solution (short barreles, subguns, etc) but the DI system has time and time again shown itself to be the better of the two for *sniper* platforms... the fact is that we are demanding more and more precision for the role every day and gas guns in any form are still suspect by many.

There are so many things that potentially go against the gas gun... repeatability of chambering, bullet setback, bullet jump, shifting of recipricating weight, magazine feed -- the gas system is just another contentious point, no matter which system it is. First shot (ccb) poa/poi is what really defines accuracy for these rifle, tiny groups is second to that... bottom line, at 800 yards a half minute is a lot.
Link Posted: 2/8/2006 5:19:05 AM EDT
Link Posted: 2/8/2006 5:33:50 AM EDT

Originally Posted By Wackypeacock:
Stoner, the French and the Swedes did their home work. Why re-invent the wheel.

wp



My new sig line?
Link Posted: 2/8/2006 7:43:53 AM EDT
Well, I had some huge sarcastic reply written out, but I realized it wasn't worth it.

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

Second off, if you have never shot the gun, seen it be shot, nor heard accuracy claims or grouping rumors, don't comment on how it performs as you obviously have no clue.

I'm no piston cheerleader, but some of the BS that gets thrown around is amazing.
Link Posted: 2/8/2006 8:12:58 AM EDT
Link Posted: 2/8/2006 8:44:21 AM EDT
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