Gas piston vs DI rifle with pictures

[slimmer13]

The big difference I have experienced, and it is big, is in operating temps and how much more quickly the action gets gummed up with DI. Piston has a huge advantage in these two areas

I have a friend that ran 900+ rounds of crappy Tula through a basic M&P without cleaning before it started malfunctioning. I think the "runs dirtier" thing is WAY overblown for anyone who cleans their rifles occasionally.

 

[oli700]

The AR is a piston design . A DI gun would have the gas traveling down the tube and terminating in a solid gas key, driving the carrier back with top force, like the op rod would. On the AR the gas key takes the gas and moves down to the tail of the bolt where it expands in a chamber and against the bolt gas rings. The pressure moves the carrier back in a perfect straight line, meanwhile the cam , cams the bolt open and the whole unit travels back for extraction .
As far as why they are still around, because it is better.
Lighter
Cheaper
Less moving parts
Genius way to disperse gas for perfect inline travel (the reason bolts peen on op rod AR's) and why op rod guns "rock" on recoil.
The forces that an op rod puts on the carrier and the "tilt" that the force wants to impart on the carrier is not a force that the AR was engineered for and shows up sooner or later .
Chamber temps ? lol, having problems with cooking off rounds ? popping primers because your cyclic rate is through the roof with a hot chamber ? lol
And a dirty gun.....shameful that it has no effect on function but a lot of effect on lazy people

 

[surevaliance]

 

[Geardo]

The AR is a piston design . A DI gun would have the gas traveling down the tube and terminating in a solid gas key, driving the carrier back with top force, like the op rod would. On the AR the gas key takes the gas and moves down to the tail of the bolt where it expands in a chamber and against the bolt gas rings. The pressure moves the carrier back in a perfect straight line, meanwhile the cam , cams the bolt open and the whole unit travels back for extraction .
As far as why they are still around, because it is better.
Lighter
Cheaper
Less moving parts
Genius way to disperse gas for perfect inline travel (the reason bolts peen on op rod AR's) and why op rod guns "rock" on recoil.
The forces that an op rod puts on the carrier and the "tilt" that the force wants to impart on the carrier is not a force that the AR was engineered for and shows up sooner or later .
Chamber temps ? lol, having problems with cooking off rounds ? popping primers because your cyclic rate is through the roof with a hot chamber ? lol
And a dirty gun.....shameful that it has no effect on function but a lot of effect on lazy people

Glad you typed this out so I didn't have to.

Dirty.... I can run 700 rounds through my suppressed pistol build in an 8 hour stretch with 0 cleaning and no issues, in the wet mud or dry dust, It DGAF.

I would wager I can do double that. Will see at the next 2 day carbine class. Will run 1500 rounds with out cleaning on a suppressed gun.

If you survive 1500 rounds in a firefight, and your gun starts to jam, and you have no ckeaning supplies, there will probably be 20 other guns lieing around you could grab?

 

[Caveman Jim]

Piston rifles were a fad that has faded fast due to false claims of longer life and better reliability. Just look at the factory built offerings and ponder why piston rifles are almost non existent these days.

I'm loving the Fad that claims of longer life and better reliability and function without having a nasty chamber every time I take her to the pit.... 4k rounds without a hickup is just fine with me.

YMMV

 

[WAYNO]

For an occasional mall ninja or can plinker shooting 20 rounds in a session, or for folks shooting varmints or at a range under decent conditions, I'm sure direct impingement is fine.

But for military use, I would have liked piston AR's. I know, direct impingement AR's, in military use, are fragile.

Now, as a civilian, with both types in my arsenal, I absolutely prefer the piston, for all the obvious reasons, except the extra weight.

 

[H2O MAN]

Two of my favorite piston driven gas guns.

 

[Boboclown]

I don't understand why gas piston ARs haven't eclipsed DI by now

Expensive and proprietary parts.

Try shooting prone at 600 yards with your VZ58.

7.62x39 is well known for its very flat trajectory and ease of shooting at distances.

Piston rifles were a fad that has faded fast due to false claims of longer life and better reliability. Just look at the factory built offerings and ponder why piston rifles are almost non existent these days.

The big names are still around. Adams Arms, Primary Weapons System, LWRC, H&K sort of exists (the army did adopt the G28, but does the MR556 and MR762 even exist in our market anymore?), Wolf is still importing their A1 upper I think. Probably forgot a few.

But I went with a simpler solution of a 5.56 rifle with an operating rod and just got an AK in 5.56 instead. Don't think I plan on buying a "piston" AR anytime soon.

 

[3MTA3]

DI vs Piston
Have both, like both, comfortable trusting my life to both. No different IMO than brunettes vs blondes, except for the trusting my life part. Interesting in that blondes and brunettes can be converted from one to the other just like DI and piston.

 

[Stomper]

Two of my favorite piston driven gas guns.
View attachment 561530

I'll see your Daewoo and raise you a (long-stroke piston) .308 Galil...

 

[Stomper]

DI vs Piston
Have both, like both, comfortable trusting my life to both. No different IMO than brunettes vs blondes, except for the trusting my life part. Interesting in that blondes and brunettes can be converted from one to the other just like DI and piston.

You didnt consider redheads.... fail.

 

[uberguy]

DI vs Piston, bla bla bla - these topics always bring out plenty of unfounded comments it seems.
Both work, fine - piston semi-autos include the venerable AK, FAL (right arm of the free world), M14/M1A and AR types. I own several of both.
Cleaning barrels is the same for all, so cleaning the BCG is the only difference.
Pistons are a solid metal rod, never seen one break. And it makes sense to have an adjustable gas-block for DI or piston to adjust for the ammunition you choose, so far as I know, pioneered on piston rifles.

Re: the OP who said "sorry Stoner" seems they may be unaware that after selling the DI design to COLT Stoner redesigned the AR (Armalite Rifle) to become the AR-180, a piston AR. COLT had better marketing and military contacts and so, we have the DI. Std. ARs are cheaper because the COLT patent expired, then the clone market exploded, and as basic economics shows, greater competition lowers prices. Piston designs share most of the same mil-spec design elements, but there has been no industry standardization of the piston/gas-block parts, unique to each manufacturer - so piston models runs a bit more.
That's about all there is to it, IMO.

 

[3MTA3]

You didnt consider redheads.... fail.

Redheads are the NFA equivalent of women and while they can appear to be blonde or other they are always redheads.

 

[H2O MAN]

I'll see your Daewoo and raise you a (long-stroke piston) .308 Galil...

View attachment 561583

Sweet!

 

[Heyjoe]

Expensive and proprietary parts

Bingo.

A spare bolt carrier for my pws carbine is over $300 dollars. That's more than half what I paid for the complete upper.

For a person interested in stocking spares for the future, commonality/obscurity of parts makes a huge difference.

 

[billstaf]

I also have a Ruger SR556 gas piston rifle. I have the FB version which I bought new in late 2011. This has been an absolutely stunning performer. Ruger easily solved the early version buffer tube wear issue by adding a radius on the back edge of the BCG. Worked like a charm. I have had other ARs in the past. All of them were DI guns. My Ruger is very much more accurate than any of them. Certainly they are more expensive to produce, and thus more expensive for the end user, but to me, well worth it. The chamber, BCG, and bolt run cool and clean. I think that Ruger has made an error by pulling the entire SR rifle line out of production. Even the 762 is no longer available. Understandably, ARs are flooding the markplace, so a high-end gun is bound to find fewer buyers. The only AR left in the Ruger lineup is the AR556 DI gun. It is cheap to make, and I suppose that is what most AR buyers are really looking for these days. My only real complaints about my SR556 are the milspec 8lb. trigger pull, but that can easily be fixed with a nice after-market trigger. Also, on my 2011 FB version, the handguard/rails are pinned in place and not removable. This means no access to the titanium pushrod for cleaning. Ruger fixed that with the later take-down version, but always claimed that access to the pushrod really wasn't necessary for maintenance. Maybe so, I can't really say. Anyone who owns one of these rifles already knows just what great rifles they are.

 

[Esam85]

I have two LWRC piston guns and a couple BCM di guns. I havent had any function issues with either. Then again I never had any function issues with the who knows how many rounds while in the infantry. Most of my failures have been due to magazines. Overall if I am going to the range i would choose the BCM i shoot faster with way less felt recoil. Oh and the BCM is about 1500 less so there is that.

 

[dwaineshort]

I think the AK47 showed us in abundance that gas pistons are not lacking in the reliability or complicated or hard to keep clean department, especially compared to the M16.

All in all though I just feel like there should be more market segment for gas piston guns. I'd rather have a gun that shoots cooler and cleaner and gives up a nat's bubblegum of accuracy (if that's even true) that my reddot that I almost exclusively use cannot even take advantage of.

If I was concerned with absolute accuracy I'd be talking about a higher powered bolt gun anyway so that argument carries almost no weight with me.

What are you talking about there's been a handful of new piston type rifles last 15 years. Acr, xcr, scar, bren 2, Tavor sar, x95, galil Ace, sig mcx, sig 556r, new ak variance, and over 20+ AR piston platforms.

 

[Esam85]

Instead of taking apart and fixing anything wrong with the piston you can simply swap out the gas tube.
I think cleaning is the same, but repair is easier with DI AR's. Hence why the military uses DI rifles, or was that not your point?

@ron I thought the same, but wasn't sure with the multitude of DI and piston rfiles so I just let that lay.

PS: I think @ron is more referring to the way recoil transfers, which I think falls more straight back in DI rifles... so I've heard.

Not entirely true the marines are switching to piston guns.

 

[Esam85]

The big difference I have experienced, and it is big, is in operating temps and how much more quickly the action gets gummed up with DI. Piston has a huge advantage in these two areas.

I find that when really running my piston gun my foregrip heats up substantially. Now i always wear gloves while shooting it.