Piston or regular AR-15

[Woodsman]

One thing to consider on piston uppers is the excellarated wear of the receiver extension and BCG. One design flaw of the piston system is the single contact point of the push rod on the BCG. This causes the BCG to push downward prior to moving to the rear causing the BCG to drag on the bottom of the receiver extension. This problem will not be eliminated until a double push rod system is developed.

The BCG tilt is one common complaint I have heard from some other knowledgeable people. It would be interesting to see how some of the various manufacturers try to address this. I'm also curious to see how HK tries to correct or minimize this in their MR series rifles.

Another related item that I have a question on is the various strokes of the piston I have seen mentioned. Some manufacturers specify theirs as a short stroke, while I thought some others stated long stroke. What is the benefit of either one?

 

[jacobswell]

I own both a DGI and a Piston and love them both. Really the only difference for me is that after a long day at the range the piston is very easy and quick to clean.

 

[pftraining_in]

Another related item that I have a question on is the various strokes of the piston I have seen mentioned. Some manufacturers specify theirs as a short stroke, while I thought some others stated long stroke. What is the benefit of either one?

The long stroke piston is designed similar to the AK piston as the OP rod is attached to the bolt. I have heard that recoil is less with this system and increases dwell time. In theory this system is easier on the rifle as the bolt is connected to the OP rod and return to battery is controlled. However the BCG is a custom part of the system and only replaceable by their system. Parts in the field would be hard to come by.

The short stroke system pushes a rod that is not attached to the BCG. This only pushes the bolt back a short distance to unlock the bolt and allows inertia to complete the bolt stroke. With this system the BCG moves to the rear and returns to battery on it's own similar to the DI system. Field part replacements are begining to be more common place, however each company still makes their own gas key conversion or one piece BCG.

Both systems rely on the springs to make the piston function. The springs are the weak point of the piston system and each company makes their own.

Long Stroke

 

[unforgiven1203]

go with gas. spend the money you save on a case of ammo and an appleseed shoot. The military has been using this design for 45 years.with periodic cleaning and lubrication it will be incredibly reliable.

 

[dukeboy_318]

having served 6 years in the military and carried this rifle in various conditions and tempatures, ive only had 3 jams with one. 2 of the jams were when i was running a blank firing adaptor and firing blanks while using Miles gear during a MOUT training excerise, aka urban combat training, and the 3rd was a result of a primer coming off the back of a shell casing during a live fire exercise and wedging itself on top of the BSG thus not allowing the BSG to come forward. I was thinking about going with a piston system for my new AR build but the more i sit down and research it, the more its becoming apparanent that its a waste of money unless you shoot on full auto or a couple thousand rounds everytime you hit the range, for me, im religious on keeping my guns clean, i clean every gun prior to leaving the range and again when i get home, even my AK.

 

[IndyDEW]

go gas! be a man!

 

[E5RANGER375]

im waiting until the military adopts one (in large), and then i will buy that one so i know that parts will always be availible and fairly inexpenssive compaired to others

 

[HD1911]

Gas...unless you are running a 10.5" with a Supressor.

 

[paramed60]

Well you all have answered my question on whether to buy piston or not. Now to find something shorter for the Bushmaster I own.

 

[Airborne33]

Well, in my opinion, neither set up is really better. Piston systems cost more because they are the latest and greatest, or so people claim.

The benefit to a piston system lays in the simple fact that it will be easier to clean the bolt, and there will be less carbon blasting back into the chamber to lock your rifle up. I have heard though, that the piston system in the long run, will cause your barrel to flex more so than the gas operated system. Comprimising longer range accuracy. This might only be a slight loss of accuracy, but it's easy to understand that when your barrel gets hot and the rod will put pressure on and off the front sight post it will cause some flex.

Normal gas operation, is a slight be lighter, arguably more accurate assuming everything else is the same, cheaper, and easier to replace parts on.

I would stick with gas operation. It's what we know, it's what works, and it's simple. Not to knock the Piston operation, or any rifles that use them.

 

[451_Detonics]

When one of the top AR makers in the world says the piston AR's are all that great I listen. John Noveske...

[DefenseReview received the following post-interview via email from John Noveske: "Also, we should mention the poor choice of platform for the piston conversion on a round receiver bore as found on the M16/M4 system. All other piston type systems out there utilize a railed receiver design, like the M14, AK-47, M249, FAL and so on. The round receiver bore design used on the M4 is only acceptable for the standard op system. The carrier and bolt expand on axis with the bore under the normal gas impingement cycle, but on a piston gun, you run into off center impulse issues with carrier tilt and incorrectly designed carrier contact points. Some designs attempt to address the carrier tilt problem with over sized carrier tails and rollers. I do not believe the receiver extension should be used in this manor. I know many people are very happy with their piston weapons. This is not meant as a knock on the piston conversion systems out there, but as a philosophical dialogue focused the new physiological relationships applied to the M16/M4 platform through the introduction of an operating system which has traditionally been applied to receivers with rails for the bolt and/or carrier. I would rather see an entirely new weapon system designed for the piston from the ground up. I believe there several outfits currently working on this."]

If you want a piston gun buy one that was designed as one, the Galil, Sig, Valmet all come to mind...not one with a half ass conversion.