View Full Version : Piston vs Gas Impingment
05-05-2012, 01:51 AM
I just got done reading the Individual Carbine Competition thread. Someone mentioned that most of them looked like the M-4 with a piston system. I was at the range last week with my A2 and someone made a nasty remark about coming into the 21st century and getting a piston system based AR. Meanwhile my toy is spitting lead like there's no tomorrow and his M-4 wonder machine can't get through a single mag without a failure-to-do-something. Also the accuracy on mine is right on. At fifty yards my target is 12 one inch squares on a sheet, 4 sheets on the target frame. 48 targets, 48 shots, no misses.
My question is what the heck is this piston crap and why do I need it. Remember to talk slow. I'm old and I'm used to Major Calibre toys.:redgrin:
Most of the piston systems are short stroke like the HK416. In a nutshell the draw of a piston setup is the ability to keep the bolt running much cooler and cleaner since the gas never enters the upper receiver and is vented out. Supposedly this allows "over the beach" and runs much better with a suppressor on SBRs.
I like the direct impingement system and I'm not sold on the pistons being more reliable. IF and that is a big IF, I was to buy a piston AR15, it would be the PWS long stroke setup. Now don't worry about that tacticooler as reality is a hard thing for those people to deal with.
05-05-2012, 03:12 AM
Oh hell. I sure didn't go 'SBR'. I have a 24" barrel with a triangular handguard and a 5" muzzlebrake. All up it's 49" long. I'm half way to the 25 yard targets before I even pull the trigger. Jim
Nowadays you have to have a short pencil thin barrel for weight savings then add 5 pounds of accessories to be considered modern and up to date.
05-05-2012, 03:32 AM
Only two major benefits to the Piston system.
The fouling that occurs over the course of 1000+ rounds is vastly reduced or eliminated.
The heat that never gets to the upper.Is this any better than DI? Probably not. However, there are several little parts that will never have a chance to fail in a Piston system (Gas Rings). I have never had a DI system fail due to fouling. I have had a DI rifle fail HARD due to gas rings.
The argument can be made (and rightfully so) that the Piston System introduces other points of failure. While statistically true, I have not seen it. But in truth, I do not have that many rounds downrange on a Piston Rifle vs. a DI.
It all comes down to the rifle, the shooter, and the maintenance. My bet is that Piston is better. But that does not mean that DI is not just as suitable.
This is the basic truth of the AR / M-16 weapons system. You can make improvements, but how much does it really improve things?
Last bit: I do believe that a Piston system will tend to make a shorter gas system more reliable and improve ballistics. The Army does not specifically test for this.
Just my $0.02
05-05-2012, 12:34 PM
I use a LWRC 10.5 inch upper on a Colt M16 lower. Its mostly intended as a close quarters weapon although it's effective out to at least 300 without issues. Its common to shot 500 to 700 rounds out of it when it goes to the range. The clean up on it is quick and easy(15 min), due to the piston system where as when I had a DI system on the lower the clean up could take well over an hour of PITA scrub, and pick.
On the other hand I have a 10.5 inch DI LMT upper on my SBR that I keep in and around the house that only gets zero comfirmed and maybe a little plinking here and there. Clean up on it isn't to bad as it isn't shot a lot. I like both rifles and neither shoots better than the other. Both are reliable but if Im headed out to shoot a lot the piston rifle will go as the easy clean up is hard to beat.
05-05-2012, 02:19 PM
we ran the old m4 pretty hard. didn't have many issues at all with the DI.
i did get to test a piston system, it had a lot of carrier bounce which is a no-no for FA. it didn't seem that much cleaner than DI to me. still got plenty dirty after a few hard runs.
the carrier bounce problem can probably be resolved for combat use.
it is a good idea, but i don't know how much "real" improvement over DI it will be long term.
i been thinking about building one but regular DI stuff and 1911 stuff keeps getting in the way!--
05-05-2012, 02:46 PM
I've seen bolt carrier bounce before in piston as well as DI systems. I use an Armforte(MGI now sells them) buffer in both DI and piston systems. The buffer eliminates bounce issues while using full auto. I also like that it reduces the rate of fire to around 650 rpm. Im not of fan of high cyclic rates at all when it comes to hand held rifles.
I also had some testing failures with some of the conversion style piston kits that you retro to you DI system. I would not use any of those kits. The quality high end stuff seems to be the way to go. LWRC, POF, LMT to name a couple.
06-03-2012, 08:55 PM
The design was made to run on DI. The way i see it if you want to get a weapon that runs a piston then get that. Old boy was probably mad because he spent a bunch of money converting his and wants everyobody else to feel his pain. I brought the same M4 overseas three times and the only issue i ever had with it was a bad mag. So just stick with your stock A2 it sounds like she treats you really well. If you really wanna shut the judges up just pull an ACR and ask if that passes their inspections. Difference between gas piston and direct impigement on an AR... Money... Thats about it.
06-04-2012, 02:09 AM
As I have previously posted, I have no issue with a DI system. The bottom line to DI reliability is regular, disciplined cleaning; this has been a simple fact of life since 1433 as it regard firearms.
I will add that powder and residue can affect a DI system more so than a piston system. Mud, dirt, and water can also affect a DI system as well. I would ask those who want to defame a DI system if they have ever done a true dirt-mud-muck-water test to an AK, FAL, HK, and AR in the same day. I have. My bottom line is that no matter who designed the weapon, they all need good attention and cleaning. Arguments about this one vs. that one have no meaning when we are talking about 1000 rounds or less.
My last thoughts: From 1868 until 1935, soldiers were issued a funnel as part of their standard weapon cleaning gear specifically so that they could pour boiling hot water down the chamber and bore to wash away the corrosive salts from the primers and powder. Oil and other solvents do not neutralize salts like water does. I have carried an M-16 or variant and used it in anger several times. I have never suffered a failure. My service began in 1982. By that time, the discipline had been instilled in the ranks. Every break you got, you broke down your rifle by sections (meaning half the squad at a time) to clean and lube as needed, then the next section (the other half of the squad) took care of theirs. I also carried an M-14 and an M-60. The same rules applied.
Even with all of that being said, I just built a heavy profile barrel DMR rifle in standard A3 dress. I will eventually replace the DI system with an Adams Arms Piston kit, and some Tacticool accessories. But that is more to please myself. The rifle shoots as well as any AR. So, the upgrades are simple choice and having some fun.
Just my $0.02
06-04-2012, 12:11 PM
I have not owned a DI system AR, but did own a P.O.F. gas piston upper. I really enjoyed shooting it and the ease of maintenance.