AR Piston vs. DI accuracy. What's the real skinny?


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Cougfan2
December 27, 2009, 07:00 PM
I've seen threads here and on other sights about the relative merits of Direct Impingement vs. piston AR's relative to accuracy. I've seen people with opinions on both sides.

I am going to purchase a new AR after the first of the year. I currently have two DI AR's. One 16" carbine RRA upper and a RRA 24" Stainless HP varmint upper, both on Bushmaster lowers.

I plan on purchasing an M4 style rifle with rail hand guard and 16-18" barrel.

My question is, "how much if any difference in accuracy is there between a piston or DI AR?". I've heard opinions that the piston guns are less accurate, but when it got down to it, they were comparing them to piston platforms other than AR's.

For out to 200 yards let's say, how big a difference in accuracy is there using factory ball ammo?

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Shadow Man
December 27, 2009, 09:04 PM
Where a piston-driven AR really shines is in its ability to divert hotter gasses and carbon fouling away from the chamber of the weapon. This results in less heat transfer to the BCG and makes for a cleaner running, cooler (temperature-wise) weapon.

Early piston-driven AR's suffered negatively in accuracy due to manufacturers attempting to shoe-horn a piston system into a rifle that was not designed for one. As soon as the manufacturers began custom-designing AR's to use pistons, those problems dissapeared as far as I know.

In summation, for a light duty weapon, you will see no difference. However, if you intend upon using the weapon for a heavy-duty gun with many rounds in between chances to clean/lube it, piston-driven gets my nod. Undoubtedly, someone will come along and tell you the complete opposite, but that has been my experience.

eatatjoes
December 27, 2009, 09:09 PM
You may find post #5 of this thread (http://www.m4carbine.net/showthread.php?t=43744) very interesting.

Tirod
December 27, 2009, 09:13 PM
The POF Para has an operating rod and recoil spring located above the barrel, which changes the reaction that the platform has compared to a traditional buffer system.

The real issue is whether a shooter has the skill to actually use the difference in accuracy. Most shooters don't practice enough or have a rifle with 1/4 MOA resolution to know. It takes a shooter at the 5 - 10K rounds a year level to see it.

As there is no standard piston system yet developed, commiting to a single source of parts supply would be more important. Can anyone guarantee their current choice of piston AR will still be in business 20 years from now? With a DI system AR, you already have that guarantee. It's been around 40 years.

Buy a AR with a hammerforged barrel by a better maker, and you will be guaranteed better accuracy.

Jim Watson
December 27, 2009, 09:16 PM
For out to 200 yards let's say, how big a difference in accuracy is there using factory ball ammo?

Nothing detectable.

Call back when you get to 600 yards with match ammo.

Cougfan2
December 27, 2009, 09:26 PM
Nothing detectable.

Call back when you get to 600 yards with match ammo.

My point exactly. If I'm shooting at those ranges, if given a choice, I would not be using a standard M4 configuration either DI or piston. I'd be using a bolt gun or some kind of M1A configuration.

Cougfan2
December 27, 2009, 09:27 PM
Nothing detectable.

Call back when you get to 600 yards with match ammo.

My point exactly. If I'm shooting at those ranges, if given a choice, I would not be using a standard M4 configuration either DI or piston. I'd be using a bolt gun or some kind of M1A configuration.

eatatjoes Thank you for the link. EXCELLENT information.

If you enjoyed reading about "AR Piston vs. DI accuracy. What's the real skinny?" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!