Gas vs Piston

What is your opinions on the Rock River Arms Entry Level tactical gun as a decent AR ? I've read some good things on this gun and the price seems decent.
 
scott585 said:
they do operate with gas systems, but the gas acts on the case rather than a piston or other part
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Actually... you are 100% wrong.

The G3/Cetme is a roller delayed blowback design. The only purpose of the chamber flutes is to ease extraction.

From Wikipedia
800px-US_Patent_3283435_8-Nov-1966_BREECH_CLOSURE_Theodor_Koch.png


Roller delayed
A schematic of the roller-delayed blowback mechanism used in the MP5 submachine gun. This system had its origins in the late-war StG 45(M) assault rifle prototype.Roller-delayed blowback was first used in the experimental MG 42 derivative MG 42V and the 1945 Mauser StG 45 prototypes. Roller-delayed blowback operation differs from roller-locked recoil operation as seen in the MG 42. Unlike the MG 42, in roller-delayed blowback the barrel is fixed and does not recoil. As the bolt head is driven rearward, rollers on the sides of the bolt are driven inward against a tapered bolt carrier extension. This forces the bolt carrier rearward at a much greater velocity and delays movement of the bolt head. The primary advantage of roller-delayed blowback is the simplicity of the design compared to gas or recoil operation.[14]
After WWII, former Mauser technicians Ludwig Vorgrimler and Theodor Löffler perfected this mechanism between 1946 and 1950 while working for the French Centre d'Etudes et d'Armament de Mulhouse (CEAM). The first full-scale production rifle to utilize roller-delay was the Spanish CETME followed by the Swiss Sturmgewehr 57, and the Heckler & Koch G3 rifle. The MP5 submachine gun is the most common weapon in service worldwide still using this system. The P9 pistol also uses roller-delayed blowback; however, the Czech vz. 52 is roller-locked.

Fired G3 case (stolen shamelessly from the internet)
DSC04649.JPG
 
It's a simple matter of this.

1) Get what you think you'd want
2) Shoot the living S#*T out of it!
3) Repeat

Thats the joys of the black rifle! You can never have JUST one!
 
both have advantages and disadvantages and both a widely used in combat the world over, why? Because they work and guys in harms way CAN depend on them. There is no one is better than the other for all applications. This argument will go on eternally as 1/2 will favor DI 1/2 will favor piston.

One truth remains, if you plan on NEVER cleaning it, a piston will always run longer, before catastrophic failure.
 
Some guns are designed to be piston guns like the Sig 550, FAL and AK. Others were adaptions of the DI AR15. Purpose built Piston guns use a bolt with a pair of large bolt locking lugs or a large breach block. They are designed to take a beating. The Stoner bolt with its 7 small locking lugs was designed for use in a DI rifle.
Accelerated bolt wear is an issue with all piston driven rifles using Stoner bolts. It has always been an issue with the AR 18 and AR180b but they were disposable guns. It was band aided in the G36 and HK416 by using much harder steels for both the bolt and barrel extension. It works however harder steels bring their own issues, like being brittle, difficult to machine or very expensive.
When the 416 was brought to market the bolt life was 20k (to be changed with barrel), then reduced to 10k with a recommended replacement interval of 5k (same as the M4). The real world is a cruel mistress.
The myth of the bolt staying so much cooler was "proven" by the initial cook off rates of the 416 being double that of the M4 (280 vs 140). This showed less heat was getting to the chamber and bolt of the piston guns. The fielding of the 416 in the IAR role has shown that 280 was a bit optimistic, as such it has been reduced to 150 in the interest of safety.

The 416 are good rifles but the individual will have to decide if they are worth 2-3X the cost of a good DI AR.
 
PWS for the win. The current line of PWS AR15`s are a really excellant all around rifle, I would love to see a PWS vs HK test.

Forget the dirt and cleaning time, the biggest downfall of a Di AR15 is HEAT. All that heat energy used to cycle the carrier is funeled into the carrier/bolt and upper receiver needlessly creating problems. Heat cooks off all your lube and is a big big factor in metal reliabillity.
 
Gunnerlove said:
Some guns are designed to be piston guns like the Sig 550, FAL and AK. Others were adaptions of the DI AR15. Purpose built Piston guns use a bolt with a pair of large bolt locking lugs or a large breach block. They are designed to take a beating. The Stoner bolt with its 7 small locking lugs was designed for use in a DI rifle.
Accelerated bolt wear is an issue with all piston driven rifles using Stoner bolts. It has always been an issue with the AR 18 and AR180b but they were disposable guns. It was band aided in the G36 and HK416 by using much harder steels for both the bolt and barrel extension. It works however harder steels bring their own issues, like being brittle, difficult to machine or very expensive.
When the 416 was brought to market the bolt life was 20k (to be changed with barrel), then reduced to 10k with a recommended replacement interval of 5k (same as the M4). The real world is a cruel mistress.
The myth of the bolt staying so much cooler was "proven" by the initial cook off rates of the 416 being double that of the M4 (280 vs 140). This showed less heat was getting to the chamber and bolt of the piston guns. The fielding of the 416 in the IAR role has shown that 280 was a bit optimistic, as such it has been reduced to 150 in the interest of safety.

The 416 are good rifles but the individual will have to decide if they are worth 2-3X the cost of a good DI AR.
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I dont see how a Di runs cooler , I have a few of each and I find it not even close. The Di AR`s I have run way hotter than my piston guns.
 
I am not saying DI runs cooler, but pointing out that the "cooler" Piston guns still cook off after 5 mags vs the DI guns at 4.66mags.

And if the parts lasted longer HK would not recommend the same bolt replacement interval as Colt does with its DI rifles.
 
This debate back from the dead is it ?

I currently run both systems. My Piston is a CMMG conversion kit.

I love DIs weight and simplicity, but I love the Pistons cleanliness.
Both run without a hiccup.

Still on the fence on which I like better.
 
KevinB said:
How hot do you think the DI Bolt gets? Not hot enough to cause an issue...
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I know my lubed up the exact same way Di guns cook off their lube way faster than my piston guns, thats a big plus for Di.
Can you do some tests and let us know?
Have you guys at KAC tested a PWS gun? How did it hold up under KAC testing?
 
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