How can I build an "ar variant" with a gas block very similar to rugers 556?

My answer is: "Difficult to nearly impossible."

But here's why.

The Ruger uses a system similar to the M-1 carbine, somewhat like a short-stroke piston system. This requires a large weight to go around the gas port/tappet and run the steel action handle back to the bolt.

The AR-15 uses direct gas impingement, which means there IS no piston, and no tappet--just a stainless steel straw which feeds pressure (gas) back straight into the BOLT CARRIER, which is actually the cylinder for the piston, which is the bolt.

Were you to change out the gas block on the AR to run a short-stroke tappet system, you would have to change your whole gas system. If you wanted exactly the same gas system, you'd have to run that big handle on the outside of the gun -- not really all that easy, especially with an alumuinum receiver.

You COULD, however, use an aftermarket piston system...it won't be exactly like the Ruger, but it will be a piston system -- this could get a bit expensive, but many believe it is worth it.

And, funny you should mention 6.8; A friend of mine, another AR enthusiast, just SOLD his 6.8; He wasn't happy with how it performed in the real world vs. the hype, and finding specialty proprietary parts were not fun...so he dumped the "nightmare" and went back to a more conventional caliber (.223).

Just saying - consider your caliber choice very carefully.

If you prefer the Ruger platform, then go with the Ruger, and put furniture on it that will make it feel and handle like an AR...THAT is going to be MUCH easier than modifying an AR action to be more like a Ruger.

You don't even have to trust me on this one...checksum me and do your own research.

The piston driven Ruger SR-556 is worth every penny. The above answerer touts that he'd rather have a Bushy or a Rock River Arms anyday, but if you're doing high volume or long range shooting, and if you clean your guns after every outing like you should, the piston drive system is worth its weight in gold.

I have done piston conversions on many AR-15's in the past few years, and to be honest, it IS worth it, and I think guys are speaking out of turn when they say the Ruger is "overpriced". Yes, compared to a "standard" AR-15, the ruger costs a lot more, but you're not comparing apples to apples. When you consider the cost of a standard AR-15 in a quality rifle like a Bushmaster or Rock River, then add a $100-150 full length top rail and quad rail forend, plus the cost of a piston system, you'll end up about $200-300 MORE than the cost of a new Ruger. The ONLY disadvantage for me for the Ruger SR-556 is that a "long range" model with a longer heavy barrel, the piston system, and a slick forend isn't available. I have two SR-556's currently, one in 5.56NATO and one in 6.8mm SPC, and both are phenomenal rifles. I've built dozens of custom AR-15's, and have owned many brands (Armalite, Rock River, Bushmaster, Colt, Olympic, DPMS, Wilson Combat, and others), and out of the box, it's VERY hard to beat the Ruger.

Naturally, variety is the spice of life, and to each his own, but the Ruger is definitely a good purchase. I'm not a fan of "tactical" rifles, with Pic rails hanging all over them, and that's the ONLY way the ruger is available, but a few hogue snap on covers trim up the forends nicely. The Ruger SR-556/6.8 6.8mm SPC is my standby hog rifle now, and I couldn't be happier.

Source(s):

I'm a custom AR-15 builder and avid AR-15 competitive shooter with deep enough pockets to test out new rifles for myself, before I buy into the second hand hear-say that people pass along like gospel...

There are adjustable gas blocks and adjustable gas tubes available. These can be used on standard ARs. Just google for them.

you can buy a Ruger upper

http://www.midwayusa.com/product/513992/ruger-sr-5...

Adcor defense has adjustable uppers

http://www.adcorindustries.com/wordpress/index.php...

CMMG has a retrofit system

http://www.midwayusa.com/product/350058/cmmg-gas-p...