Direct Impingement vs Gas Piston AR.

[Biggsly]

I have been shooting ARs for over 20 years and I have owned a bunch of them. I have never fired a piston AR until today. I had a chance to play with 3 of them that belong to my B.I.L. 2 of the guns run the Adams Arms kits and one was a LWRC piston rifle.
I will say that the piston shoots smooth and the gun stay a lot cleaner.
Here is my question.

What are the goods and bads of the piston vs a D.I. AR?

 

[doctorjj]

The original Stoner design is a piston design. The aftermarket "piston" designs could more properly be called op rod designs. The op rod designs take the heat and fouling and move it to a different place on the gun. It still gets hot and and dirty. Maybe if you are doing sustained full auto, this might be beneficial. I think they are nice for extremely short SBR's and for suppressed use to, to provide potentially better reliability in the extremely short barrels and for less gas in your face when suppressed. Adjustable gas blocks can mitigate that as well though. The bring with them a slew of problems though, including non standard parts, less accuracy, BCG cant or tilt, and excessive wear on small bolt lugs which were never intended to be operated from an op rod. Unless I were going extremely short SBR or SBR and suppressed, I don't see the benefits.

 

[tulsanewb]

I have been shooting ARs for over 20 years and I have owned a bunch of them. I have never fired a piston AR until today. I had a chance to play with 3 of them that belong to my B.I.L. 2 of the guns run the Adams Arms kits and one was a LWRC piston rifle.
I will say that the piston shoots smooth and the gun stay a lot cleaner.
Here is my question.

What are the goods and bads of the piston vs a D.I. AR?

I only know a little, but as I understand the big draw-back with piston guns is carrier tilt, where the gas is hitting the bolt from above/off-axis and causes the bolt to rub/wear. A lot of the newer designs are supposed to address this better. They are definitely cleaner, especially for suppressed fire.

That's the extent of my knowledge.

 

[Biggsly]

Thanks guys.

 

[Maverick1911]

The original Stoner design is a piston design. The aftermarket "piston" designs could more properly be called op rod designs. The op rod designs take the heat and fouling and move it to a different place on the gun. It still gets hot and and dirty. Maybe if you are doing sustained full auto, this might be beneficial. I think they are nice for extremely short SBR's and for suppressed use to, to provide potentially better reliability in the extremely short barrels and for less gas in your face when suppressed. Adjustable gas blocks can mitigate that as well though. The bring with them a slew of problems though, including non standard parts, less accuracy, BCG cant or tilt, and excessive wear on small bolt lugs which were never intended to be operated from an op rod. Unless I were going extremely short SBR or SBR and suppressed, I don't see the benefits.

+1 on this. I looked into them as well. They do stay a bit cleaner but the piston setup and its parts are proprietary. If company "A" goes out of business and you have an issue down the road that requires a replacement part...well, you have a 10lb. Paperweight.

 

[SPDguns]

The op rod designs take the heat and fouling and move it to a different place on the gun. It still gets hot and and dirty. Unless I were going extremely short SBR or SBR and suppressed, I don't see the benefits.

This is true! IMHO the op-rod design is just another expensive gimmick to bolt on so you can brag about how much you spent on "upgrading" your AR. The gas system has been working for how many years now???

 

[DFarcher]

Piston AR = solution to a problem that does not exist. If you like ARs and like to tinker/build rifles the piston guns are definitely not the answer, lots of proprietary parts from mfg to mfg.

 

[AKguy1985]

I'm a DI guy myself. Never owned a piston AR and dont plan to.

 

[aestus]

Carrier tilt is no longer a problem with new piston designs. I would say that any piston gun or piston conversion bought in the last 2-3 years won't have carrier tilt problems. Most people who claim carrier tilt as a problem are just regurgitating stuff they heard or read on the internet more than 5 years ago. Most companies that offer piston AR's or piston conversions will usually have a 1 piece BCG where the gas key and bolt carrier are machined out of 1 piece. Also, if you look at the tail end of the BCG, you'll noticed that they are slightly ramped, especially towards the bottom. This keeps the BCG more centered on impact with the OP-Rod.

The downsides are the following:

1) Extra weight on towards the muzzle. Typically piston AR's are about a half a pound heavier than DI type guns. LWRC and LMT probably have some of the lightest piston setups currently on the market. With that said, a DI gun will always feel lighter and often will be better balanced with less weight.

2) Proprietary parts. This is especially true with the boutique manufacturers like LWRC or PWS, ect. Adams arms based rifles and conversion kits seem to be more readily available if you need spares. The weakness in piston AR's is usually the piston spring (if the system uses one) and in older LWRC's the piston spring cup. Newer designs tend ot be more robust and will last the lifetime of the firearm. Older models required a spring replacement every 5K - 20K rounds.

3) Limited handguard / rail selection. Depending on the size of the gas block for your piston setup, you may or may not be able to use the latest skinny handguards that run the length of the barrel like what all the cool kids are doing now LWRC uses a proprietary receiver/barrel nut mounting system so 3rd party handguards are almost not an option for some of their models.

4) Heat. I hesitated to put this on the list. I shoot with my support arm extended on certain shots and often shoot with no gloves on. There's no issues when I do it with my LWRC, even though my hand is essentially grabbing right around the gas block and piston. With that said, with sustained fire with high consecutive round counts (like in a rifle or 3 gun match) that piston and gas block with get hotter than the sun and will completely burn the **** out of your hands after hundreds of rounds. Even with gloves on, once that gas block goes nuclear it stays hot for a long time. If you're an AK shooter, you're probably used to dealing with hot gas tubes and gas blocks, though so may not be an issue.


SBR's is where pistons really shine. Less gas blown in your face and less prone to finicky cycling due to short barrel lengths and gas pressures. If you're a ninja and shoot in and out of water all the time, it's another area where pistons shine. Otherwise, the benefits are negligible.

 

[uncle money bags]

I concur with aestus, almost.

A penny worth of black RTV or house hold silicone and a BCM charging handle practically eliminates any gas to the face on an sbr, even with a can.