AR piston versus DI - an honest debate

[captain awesome]

what he doesn't know won't hurt him

I can picture it now, he goes to the range, and loads his mag, gun fails to operate....
buddy; "dadgum DI ar15. broke again. I am getting piston AR next time."

 

[breakingcontact]

From 1858

This topic again ...

I've owned a pair of POF gas piston ARs for about four years with zero problems. The op rod and piston don't add any significant weight and POF has every spare part you can imagine at reasonable prices so parts and availability are a non issue. If you shoot full auto suppressed you'll appreciate an oil-free bolt carrier.

I also own DI ARs but would sell them before the POFs. There are lots of opinions about gas piston ARs with most of them coming from folks with little to no experience with them. So what's new right? If you don't want a gas piston AR then don't buy one. There are far more important things to worry about.

and from Powder

OP wanted opinions on why/where the Mil was going with it's pistons, not another dogfight.

Suppressors on piston guns. Period. Stop.

Most of the people who actually have quality piston guns, I have found, do prefer them.

I'm with Powder on this. Honor the OP's question. Military and pistons? Who knows what they will do and when, but figure on money and not just performance being a main determining factor.

For the rest of you all, enjoy your DI guns, nothing wrong with them, stop bashing on the piston guns. It will be OK. You can keep your 1911's too, they are nice, even though Glocks are better guns overall.

 

[back40]

of course guys with piston guns prefer them...they did buy them afterall. you ever notice how most folks will champion what they own? and i never bashed the piston guns, so stop trying to pick a fight. especially considering that you still can't answer a simple question when asked.

 

[HKGuns]

Understood, I was making the comment for the casual observer.

Misunderstood since you quoted me. All good.

 

[HKGuns]

of course guys with piston guns prefer them...they did buy them afterall.

Not trying to pick a fight with you but there are more than a couple of posters who own both, myself included, that like both because both go bang and send lead down range when you put your booger picker on the trigger.

I especially like one thing about my piston, as stated further up in the thread. But that is just me....as also stated earlier in the thread not everyone values ease of cleaning as much as I do....

Both are reliable and viable....It is GREAT to have choices.

 

[back40]

i agree, hk. i was simply saying that if you've bought one you likely have justified it and prefer them. me, i can't justify one for reasons stated earlier. otherwise, if i had pulled the trigger on that POF, i'd probably be loving it right now.

 

[Fishbed77]

Im leaving out: (according to fishbed)

-less expensive...good call there
-better balance (typically less nose-heavy)...really? Hit some weights
-no carrier tilt issues...old issue, been solved
-ability to mount extended forearms (no gas regulator to obscure)...isn't an issue to me, may be to some
-common parts availability...been addressed
-less expensive parts...perhaps a bit, but what's more likely to break?
-easier part replacement...I suppose so. With a DI gun just swap out your broken bolt carried/BCG after youve broke it by heating it up

Price is a good point. M&P Sport for instance is a great gun for $750.

Breakingcontact, if you don't understand the difference between weight and balance in a firearm, there isn't really much left to discuss here.

 

[breakingcontact]

Breakingcontact, if you don't understand the difference between weight and balance in a firearm, there isn't really much left to discuss here.

Ha. Take it easy. Whatever works for you. A piston AR is not like carrying an M1A and a DI isn't feather weight. If in your world it makes a big difference for weight or balance, rock on. Not a big deal to me.

 

[ugaarguy]

I'm with Powder on this. Honor the OP's question. Military and pistons? Who knows what they will do and when, but figure on money and not just performance being a main determining factor.

Very well written, sir.

For the rest of you all, enjoy your DI guns, nothing wrong with them, stop bashing on the piston guns. It will be OK. You can keep your 1911's too, they are nice, even though Glocks are better guns overall.

Breaking Contact, there's no need to stir up more emotions by bringing up the always controversial Glock vs. 1911 debate. You also need to take your own advice and quit bashing DI AR-15s, particularly when you can't even distinguish between the bolt and the bolt carrier group. You've also demonstrated that you don't understand what causes AR-15 bolts to break, nor under what circumstances. It's not heat, and switching from the bolt carrier located piston to a gas block located piston isn't going to solve the problem either.

Now I notice a lot of manufacturers are using piston systems. These seem to be better than the piston-kits that were offered for builders and suffered from carrier-tilt.

The new piston AR-15 uppers that aren't retro fit designs have mitigated (not eliminated) carrier tilt, but the various manufacturers still haven't standardized the parts.

Of particular note, is that the SOCOM units are now using the HK416, which is a piston-design evolution of the Stoner rifle (at least that's how its been described to me, please correct me if I am selling the 416 short in its design). The primary question is, if piston systems are not superior when masterfully constructed, why are the top operators using them when they have free reign to carry whatever they want?

Using SOCOM is a bad example. Those troops have access to a mind blowing amount of non-standard equipment that's chosen for specific missions.

There seems to be talk that the next evolution of the Army's main infantry rifle will be a piston design. I know this is a perennial topic as well, but the piston design seems to be in favor amongst manufacturers.

It probably won't be an AR-16 / M16 / M4 family weapon either. It will likely be a ground up design like the FN SCAR, HK G36, or something else not even manufactured yet.

Therefore I ask the question: if you need an absolutely dead reliable carbine, do you go with a factory piston system or DI?

In an AR-15 carrier located piston vs. gas block located piston isn't going to determine reliability. Build quality and parts quality are going to be the major factors. It's going to be far easier and less expensive to get a properly built AR-15 that has the original carrier located piston.

 

[kwguy]

I put a Failzero bcg and upper receiver onto a DI AR, and got rid of most of what I consider to be the slight disadvantages of the DI platform: Ease of cleaning (or the lack thereof), and the 'dirty nasty lube' issue. It still gets hot back in the receiver, but only needs about as much lube as the Adams arms piston AR, which is very little.

 

[Bartholomew Roberts]

The primary question is, if piston systems are not superior when masterfully constructed, why are the top operators using them when they have free reign to carry whatever they want?

Because they have specific requirements that aren't being met by the M4/M16? Some of the things the 416 reportedly does better are handle the change in dwell time on short barrels that are only occasionally suppressed and over-the-beach jobs where there is no time to drain the M4/M16 gas tube prior to firing.

There seems to be talk that the next evolution of the Army's main infantry rifle will be a piston design. I know this is a perennial topic as well, but the piston design seems to be in favor amongst manufacturers.

Not going to happen. The Army just killed the Improved Carbine Competition saying there was no substantial improvement and several of the entries were just upgraded piston M4s. The Air Force is currently discussing killing both the B52 and B1 bomber programs due to budget. So I am doubtful the U. S. Army is going to drop a system that is working well for an incremental 0.x% improvement in reliability (In the now infamous dust tests of 2007, the M4 had a 98.6% reliability - so there is really just not a lot of room to improve).

Therefore I ask the question: if you need an absolutely dead reliable carbine, do you go with a factory piston system or DI?

The issue between piston and DI as a general issue infantry weapon isn't actually one of reliability but improved life cycle costs. For example, there was once a proposal to give each deploying SEAL team two M4s. The problem was they would get a new M4 prior to deployment; but they would shoot so much during the 6 month work up that the rifle would be worn out by the time deployment rolled around - and then they would have to deploy with the worn out gear.

With the M4, you have taken parts that were designed 50 years ago for a 20" rifle amd crammed them into a shorter carbine with a faster cyclic and twice the port pressure. You've increased the loads on the bolt ~150% without changing the bolt design. And then to put the cherry on top of this sundae, if you are the Army, you've just adopted a higher pressure lead-free ammo (M855A1) that tears up bolts and barrels even faster.

At some point, you are going to see a cost advantage in having a newer rifle (whether DI or piston) that needs less frequent parts replacement. To give just one example, the Knights SR15 has a redesigned bolt, barrel extension and gas system. Still a DI rifle; but much hardier than an M4. I imagine the 416 has a similar advantage since it isn't trying to be backwards compatible with parts used for a 20" rifle 50 years ago. I think that probably plays a larger role than the operating system.

Your average recreational shooter will never get within 5000 rounds of the M4's life cycle under an extremely heavy shooting schedule. So arguing which is more reliable for recreational shooters is kind of pointless - although it remains a popular Internet past time (and not just in regards to DI vs. piston; but a whole range of AR related parts questions).

And for those shooters who do approach those numbers, you have to look at the specific circumstances; but sometimes it can be more cost effective to replace cheaper, easily acquired parts more frequently than to replace expensive, proprietary parts less frequently. For example, there was once a manufacturer offering barrels made out of super steel used for artillery that would last twice as long as your typical AR barrel. The problem was the barrel cost 3x as much, so nobody bought it. Another example, using cheap Russian ammo, you might have to replace a barrel every 6k rounds instead of every 10-12k rounds; but you save enough money that you can buy two extra barrels and still come out ahead on cost.

 

[Robert]

84 and 86 hit the nail on the head. But still far too much bickering to leave this open, wo I am going to add this to the long list of closed Di vs piston threads.