View Full Version : ar newbie

August 7, 2012, 08:12 PM
what is the differance ( pros and cons) between piston and gas ar's? I am not familar to the ar platform. I will be buying one soon, but before I buy, need some learning.


August 7, 2012, 08:23 PM
I'll just sit back and enjoy...

August 7, 2012, 08:32 PM
Awwww... izzat any way to be? ;)

Hey bluewookie... use the search engine OK? It takes several paragraphs from more than one perspective to explain the whole DGI vs. Piston thing properly... and it's already been done more than once. See here (http://thefiringline.com/forums/showthread.php?t=496679&highlight=gas+vs+piston) for a recent one.


August 7, 2012, 09:17 PM
i am using the search now.

August 7, 2012, 10:05 PM
You want an AR for rapid fire, and basically abusive use? Go piston, and don't forget the chrome lined barrel.

You want more of a target gun or for hunting? DI, and a long stainless barrel.

This barely scratches the surface, but is generally a place to start you thinking about what you want to achieve.

August 8, 2012, 12:38 AM
For your first AR you'd be wise to stick with DI. As you learn more and are ready to buy your second (a very common occurance!) then do the pros and cons. :p I'm on my third and have stayed with DI but there are plenty of arguments the other way.

August 8, 2012, 12:53 AM
i am using the search now.

Love ya'! :D


August 8, 2012, 02:09 AM
Since you are new to AR's, just go with a DI rifle. It is the most common system and is the original design of AR15. Worry about Piston when you get more experience with it.

August 8, 2012, 08:17 PM
more to the reason for asking. i am wanting a 50 beowulf. but before i buy i needed some advise. i want a big bore ar. i carry a delta elite. i will be hunting and we have a lot of engine blocks and stuff to reak carnige on. i will build my ar collection from there. Buget is around 4500.

August 8, 2012, 09:26 PM
I wouldn't recommend a big bore ar for a person new to the ar world. i would recommend you build a 5.56/.223 ar on a thousand dollar budget. Here are the specs i recommend: DI gas system, mid length gas system, 1 in 7 twist 16 inch barrel , rock river national match trigger, flat top upper, free flat handguard of some sort, magpul mbus rear sight, np3 plated bolt carrier such as wilson combat, and a milspec buffer assembly.

i recommend that you build your first one to get the feel for the system and learn how it works. Also when you build your first ar video tape the whole thing if you can. Than if you want a big bore ar just get a new upper. With a budget of 4500 you can afford to build an ar and get a new upper and buy a few thousand rounds of m193:D

Good luck.

August 8, 2012, 09:33 PM
I'd build the rifle cheaper than $4500.. cuz you will need that much for the .50 Beowulf ammo.

August 9, 2012, 06:16 AM
i recently has the same curiosity as the OP... and heres what i learned...

pistons in fact do not add reliability to the rifle... a direct impinged system is essentially a short stroke system, but instead of a piston its a quick burst of air, so the force doesnt ride the carrier all the way back... if theres any grit on the receiver itll stop a piston system from cycling just as fast as DI

you will have a noticable decrease in accuracy

with a rifle that operated at temperatures well into the hundreds of degrees, a piston only reduces internal receiver heat a very, very small fraction of it, not even noticable

so... with a decrease in accuracy, no gain in reliability, and roughly the same interior receiver heat, you'd pay more for a heavier rifle with more moving parts that would in turn give you a higher possibility of a breakage as you now have more parts you can actually break... plus you might have to deal with carrier tilt, many people dont, but some do, and itll tear up the inside of your upper receiver if you get it

in short.. id save the money for better optics instead.. like a nice eotech or trijicon


if youre looking for more punch in the AR15, look into 6.8mm conversions, with newer SPCII chambering, new mags, and better twist rates, you can buy ammo thatll turn the AR15 into a reliable 800+ yard rifle, delivering over 500ft/lbs of energy past 800 yards so long as you have the accuracy to hit the target (which a DI system will provide)

August 9, 2012, 09:17 AM
pistons in fact do not add reliability to the rifle... a direct impinged system is essentially a short stroke system, but instead of a piston its a quick burst of air, so the force doesnt ride the carrier all the way back... if theres any grit on the receiver itll stop a piston system from cycling just as fast as DI

you will have a noticable decrease in accuracy

There are 2 things i disagree witth in your post, First, a piston operated system adds reliability with the fact that it can operate filled with water or mud, but who does that to their rifle:D and 2, you don't have to clean your rifle often. My p415 went 6500 rounds before i cleaned it, not because i had to, rather because i wanted to... Not all piston ars have issues with stringing. My p308 puts my buddy's SR25 to shame at all distances, Even after it had a lot of rounds through it. You can't argue with 1/2 moa at 1000 yards.

August 9, 2012, 04:23 PM
I disagree that DI is any more accurate than piston. Accuracy will have way more to do with a) the shooter, b) the trigger, c) the barrel and d) the ammunition, particularly the degree to which the bullet has been matched to the twist rate of the barrel and the degree to which factors such as optimal seating depth have been accounted for.

I do not know if a piston gun can be more accurate than a DI gun. I will tell you my piston gun is more accurate than the COLT .223 HBAR I had in the late 1990s. Some of that has to do with my maturity as a shooter then vs now, handloaded ammo, and the fact that the COLT was an A2 with integrated carry handle, which made mounting optics harder (specs for my gun are at bottom). Some of it though has to do with the very smooth operation of my weapon as its built.

As to the question of heat buildup in the receiver, a piston gun is absolutely without argument cooler running. I shot 200 rounds last weekend and my receiver was barely warm to the touch.

One myth about piston guns is that they are much cleaner. This isn't entirely true. Yes they are cleaner running in the receiver. After 200 rounds i can wipe my bolt carrier group and barely get a smudge off of it. A DI gun is filthy after 200 rounds. Just is. However all of the soot that isnt going in the receiver has to go somewhere. It gets on the piston's gas block and leaves fouling in 3 areas: the piston gas block, the barrel underneath the handgard, and the gas piston itself. I always clean these components after shooting, so having a piston gun isn't saving me any time on gun cleaning. Could it run just fine without such cleaning every time, sure. So can a DI gun nowadays.
So in summary, a piston gun just gets dirty some place else. Ditto the heat - it gets hotter than a DI gun in the same areas that get dirty.

So Pros and cons:

DI - Pros: original design, proven, millions of guns in existnace, prevalence of parts, originally military spec., can be lighter weight given less metal up front

DI - Cons: heat conveyed to the receiver, additional fouling delivered the bolt carrier group and receiver

Piston - Pros: Cooler operating at the receiver. Cleaner in the receiver. Theoretically this could yield longer life and greater mean time between failures to extract or to load.

As a point of reference I have shot my Piston AR-15 2000 times since building it without a single misfeed or failure to eject. Many DI advocates will note they have gotten the same performance. Not all DI guns nor all piston guns perform that well.

Piston - Cons: heat and dirt on the other end of the gun. Possibility for carrier tilt, especially on earliest piston systems (basically eliminated these days if you buy a quality piston system).

It's a wash, really. Its ultimately a shooter's preference as to DI or Piston, neither is inherently more accurate or more perfect than the other. I might give a slight nod to DI just based on the millions of DI ARs in existence making it a more proven system over time. It will be a long time before pistons prove that kind of performance over that long of a duration. It is well within reason to expect piston guns to perform extremely well though.

Specs of my particular gun:
-Black Rain billet upper and lower receiver and flash suppressor
-Adams Arms 1:9 Twist 16.5 inch barrell, Adams Arms piston system, includes Adams Arms Bolt Carrier Group
-Milspec mag release, selector and battery assist with Magpul BAD
-Timney Trigger with anti-walkout trigger group pins
-Yankee Hill Machine front and rear BUIS
-BCM Gunfighter Extended Latch charging handle
-Magpul collapsible rear stock and Hogue grip
-Midwest industries aluminum quadrail w UTG covers
-UTG vertical front grip with flashlight
-Magpul PMAG 30s
-EOTech XPS2 65 MOA ring and 2 dot sight w a Sightmark 3x Magnifier on flip to side mount (cheap but works)