Evening /k/, was wondering if I could get a gas piston vs DI thread going?
I'm building my first AR, and completed my lower last night. Now, (amongst many other decisions) I'm trying to decide if a gas piston is worth shelling out for.
The purpose of this build is first and foremost to have something for self defense/SHTF gun (call me a paranoid, I just don't like the way things are going these days). But, I do plan on taking it to the range for a bit of fun/practice every other week or so.
With all off that in mind, reliability and lightness seem to be the two most important factors. I'd imagine that as a defensive weapon, I'd never be engaging anything at more than 100 yards -- in other words accuracy seems secondary.
So, if we could assume money isn't a huge factor, are there any downsides I should be aware of? I've seen some people online saying "dont put a gas piston in something that was originally designed for direct impingement". But I can't find any info on why that would be -- other than opinionated-sounding conjecture.
So, help out this newb, critique his assumptions, and give your two cents on the DI vs gas piston thing.
I have a spike's tactical forged lower and CMMG parts kit -- if that matters at all. I haven't chosen an upper, but I think I want to stay forged and A3.
Pic related, I'm thinking about buying that upper. But I can only find completed ones... I want to know how to fix my gun if it breaks, so a built one seems like it might be a bad idea. Just a thought.
>>28032357
>But I can't find any info on why that would be
carrier tilt. pistons can push the bolt carrier back at an angle (whereas a DI system would not) and the bolt carrier ends up contacting the bottom of the buffer tube
>>28032357
>I want to know how to fix my gun if it breaks
Gas pistons arent standardized for AR pattern rifles, each company makes their own piston/springs etc all proprietary and non interchangable. So no, for an end of the world SHTF gun you don't want a fucking piston AR. Just buy a DI gun, it lets you use any standard bolt carrier group and gas tube that you can find at literally any gun store in America.
tl;dr: want a piston? get an AK
Piston ARs are a solution looking for a problem. Doing nothing while creating a dozen extra problems that weren't exactly there before.
Enjoy your added weight, cost, premature part wear and breakage, and more for absolutely no benefit. Assuming you go with a piston operated gun.
>>28032402
>So no, for an end of the world SHTF gun you don't want a fucking piston AR.
>each company makes their own piston/springs etc all proprietary and non interchangable.
So you're telling me DI is more reliable or parts are more readily available? I've read that there are kits that that work with numerous manufacturers (I think Adams or something is one of them).
>>28032436
Holy shit, that gun vibrated like a sine wave.
>>28032438
more available for sure
if you break a part on a normal DI BCG you can grab same part from any other DI BCG and slap it in
it's like if everyone plays with legos and then you decide to buy megablocks instead
>>28032402
I'm not an AR piston, but this.
A DI gun is going to have more shared-parts than any piston, due to standardization. And, though I'm not certain, I believe the military uses DI.
>>28032438
The reliability aspect is overhyped. A good DI gun is just as good as a good piston gun. However, the DI system is standardized but piston is not. There MAY be some different manufacturers that can use each others piston parts, but in general, each manufacturer's piston parts, springs, and bolt carrier groups are non interchangeable. And even if you had a piston gun that worked with several different manufacturers parts, how likely are you to find replacement parts in a SHTF situation? Probably never.
Piston does solve the issue of having excessive gas blowing back in your face if you suppress a DI gun, but otherwise has downsides with: weight, slightly more recoil (piston is more mass moving back and forth), and the lack of standardization and ease of finding spare/replacement parts.
Since you said your main goal was a SHTF gun, then you do not want a piston AR. A good DI gun is good. You just need to lube it up every 1000rds or so and that bitch will continue to run no problem. That is assuming you buy a good upper from BCM, DD, etc.
>>28032468
if you use super slow mo cameras you can make a lot of things look like they are made of jello
look up some AK vids
>>28032479
yes the military ARs use DI with the exception of the ones that are specifically piston (SCAR, okay that's not really an AR but kind of, HK416)
>>28032479
Military most definitely uses DI milspec parts.
>>28032357
Three points for you to consider.
1. You shouldn't be using an AR for self defense (unless it is among the few ARs not chambered in .223). You should use a .308 or 12 gauge shotgun. Carry a .45 pistol on your belt in case you can't get to your long gun in time.
2. You don't really need semi-automatic fire. A skilled markman can operate a bolt action rifle almost as fast as a semi-automatic one.
3. Direct impingement is a jamming hazard.
>>28032506
Well no shit AKs do it, they're piston too.
I looked up some DI AR slow-mo stuff right after posting that they don't vibrate like that at all. Makes sense because all the movement of the parts is strictly forward and back.
>>28032524
Top bait.
>shtf gun
>reliability important
>accuracy second
You dun goofd not getting an AK.
At this point I'd say go DI and get a short gas system. The shorter system runs more reliably when fouled as more gas is pushing the bolt back, at the expense of increased wear on parts. Again just get an AK and you don't have to worry about having it perfectly cleaned and lubed with the best stuff all the time. ARs can be divas sometimes and that's not a meme.
>>28032573
http://www.calguns.net/calgunforum/showthread.php?t=1118901
yeah, AK will take even more shit, but an AR can still take a good amount of shit too.
>>28032470
OP here. That makes sense. But, I'm assuming that in a SHTF scenario, I'm going to wilderness, or maybe a piece of land my parents are wanting buy. With that assumption I'm also assuming lots of parts wont be around. So I want something that lasts on its own... To me piston sounds like it lasts longer.
>>28032573
>lol just overgas it
Shit advice.
OP. Learn about gas system lengths, barrel lengths, buffers and the relations between the three.
Then you'll understand the system and how to make a light-shooting, reliable gun.
>>28032573
I'm only $150 into the build. If this is true I'm open to hearing your assumptions as to why this is true. If someone could convince me I'd sell what I have so far and buy an AR immediately. But, the lightness of 5.56 and greater availability of the round (my perception) seem to trump the AR.
>>28032482
>lube it every 1000 rounds
The issue with DI is excessive fouling. You have to set aside time to keep the thing clean, even in an shtf scenario. If you feel you can do that and have all the tools/lube necessary then an AR may work for you. Its going to be a bit more work to keep it running smoothly. Imo its not a good choice of combat rifle for an individual. We don't have all kinds of logistics backing us ensuring we always have the right cleaning parts and lubricants, we don't have a base we can fall back to every night and clean our rifles. You may be out in shit for a few days before you feel its safe to disassemble your lifeline. You may be in environmental conditions that are not ideal for the gun's design. You open yourself up to many chances of failure if you aren't able to keep the rifle clean.
>>28032643
>If someone could convince me I'd sell what I have so far and buy an *AR* immediately.
I meant "AK"
>>28032643
He's spouting memes. People have shot ARs for thousands of rounds without cleaning and they performed fine. It's not a concern unless you plan on beating your rifle like it's your wife.
>>28032644
It's pretty clear you have no idea what you're talking about.
ARs run fine for a long time assuming they're properly built and at least slightly lubricated, like any gun or machine, really.
>See "Filthy 14"
If you are building an ar. Go di.
If you want to buy a piston ar buy a HK
>>28032608
>wilderness
You mentioned liking the .223 round, for that to be ideal you need open environments like a desert. It doesn't perform well after hitting brush/bushes and won't cut through a tree like most 7.62 rounds would. An AK will cut it, even 5.45 is said to go through small trees and light cover pretty well, while .223/5.56 is more likely to start to fragment.
A heavier 7.62 round like a .308 would be more ideal, but if weight is another concern the round itself is heavy and the guns that shoot it are too. Stamped AKs are pretty light, just a bit heavier than an AR, and 7.62x39 certainly has adequate barrier penetration. That's one of THE go-to choices for forest/jungle warfare.
According to Battlefield Las Vegas, ar15s last longer than ak47 or akm.
The part that breaks on the ar is the cam pin.
The akm have the trunion or reciver crack.
>>28032702
Thanks for the input, /v/
>>28032644
seriously, look at http://www.calguns.net/calgunforum/showthread.php?t=1118901 even if all you do is look at the photos in the first post
the guy is treating that cheapo psa gun like total shit minus dumping it in a pile of cow droppings and it's carrying on pretty well.
>>28032696
>7.62 will go through cover fine
>.223/5.56 won't
>but 5.45 will
How the fuck do you figure that? 7n6 is lighter than any non-varmint .223/5.56 loads. Are you retarded?
Goddamn slavaboos.
>>28032709
it's a rental gun range in Las Vegas where full auto is the norm
>>28032593
>scrubbed it and oiled it but still had failures
That's what I kept seeing throughout the article... Personally I'm not worried about the gun being able to be dragged through sand or run over by a car, none of that is a test on the guns performance reliability. Any gun should be able to withstand that, its a hunk of metal.
>>28032696
That makes sense.
Stamped AK sounds good too. But I don't know too much about AKs (yet). What kind of reliability can you expect from a stamped example?
Thanks for your response.
>>28032702
I cant tell if you're being serious, but I'll just go ahead an assume you are since rest of your comment seems serious.
I'm not going to take advice from a video game, but thanks.
>>28032735
>>28032709
http://www.thefirearmblog.com/blog/2015/09/08/ar-endurance-findings-at-a-rental-range/
http://www.thefirearmblog.com/blog/2015/06/03/how-many-rounds-can-an-ak-fire-before-it-breaks-down/
>>28032733
Sorry, my bad, didnt mean to be rude. Thanks!
>>28032725
I admit I'm literally basing that on lore. Its documented that 5.45 will rip a guys limb off ("devil's round") and I've heard plenty of places that it will go through a tree of decent thickness. It tends to stay together better than 5.56, as IRS designed to yaw and tumble rather than fragment. Still neither have much on a 7.62 when it comes to penetration.
>>28032752
Reading these now. Half way through the first. Pretty interesting, thanks!
>>28032794
>I'm literally basing that on lore.
Now it makes sense.
Please stop posting baseless and incorrect information.
>Its documented that 5.45 will rip a guys limb off
Wat, where is it documented?
Same place that says a .50 BMG round will kill someone just by passing by them?
Seriously, just stop.
>>28032357
>AR DI
More cleaning and lube utilized to keep the rifle from jamming. It isn't bad but if your in a limited resource value as you said in the the thread OP, not a good choice. Still AR DI is a pretty good system just like other gas operations but Stoner's version puts gas directly into the moving parts. Check out the DI system of the MAS 49/57.
>Short stroke piston
Uses more parts but less recoil than a long stroke piston. Uses slightly more resources to clean and maintain than a long stroke piston but is fouled less compared to a DI (Literally the middle man of the two)
>Long stroke piston
It's simpler to clean and less resources to maintain, however, it influences recoil heavily, bringing in more force. Unless you give it a compensator (If that's even legal) or utilize the counter weight piston (Like in the AEK-971) with a shock absorption stock, you could reduce recoil both felt recoil and recoil.
>>28032752
>We no longer use ANY piston conversions or factory pistons guns with the exception of the HK-416 “knock-off” TDI upper. I purchased a FACTORY brand-new MR556 and it started keyholing after only 10,000 rounds. - See more at: http://www.thefirearmblog.com/blog/2015/09/08/ar-endurance-findings-at-a-rental-range/#sthash.3KzmpbBD.dpuf
Would have never expected to read that. I'm sold.
>>28032735
>what kind of reliability from an AK
AKs are considered one of the most reliable firearms, if not the most reliable in history. Check out some torture tests, again yeah you can run most guns over, but that's not too realistic of a scenario. What you should carefully about is how well it will fire with twinkies stuffed in the receiver. You never know when your snacks are going to get misplaced.
I'll add that I'm not implying ARs just shit the bed afrer 100 rounds if you don't clean them. We're talking about situations that are unlikely to occur, like not being able to keep the rifle clean or actually running into someone hiding behind a tree/wall/car... well I consider that to be pretty likely as people don't just stand there and let you shoot them which is why penetration capability is one of my primary concerns. But that's not to say a green tip 5.56 round isn't adequate. The AR platform is indeed adequate and rightfully earned its place among the top rifles in the world. We're only discussing minor pros and cons.
>>28032643
There are AK's and AK variant weapons that shoot 5.56. However there are other types of ammunition that's abundant like 5.56 (6.5 Grendel, 6.8 Remington SPC, etc)
>>28032832
I kind of contradicted myself. It was documented in the Soviet invasion of Afghanistan. And did you bother to look up the penetration capabilities of 5.45 compared to 5.56? The burden of proof may be on me but obviously I'm too lazy to pull up all the sources I've seen. Search for them or remain wilfully ignorant.
>>28032725
>How does it go through!?
Because 5.45 tumbles when it hits an object causing it to break light cover (Sort of like a drill), unlike 5.56 that fragment. Do you even ballistic bro?
>>28032357
For reliability a good DI rifle will be just fine. Properly tuned, literally all you need to do is apply some kind of lubricant every few hundred rounds or so. InRangeTV has videos showing that the AR15 does just fine in sand and mud conditions as well.
Piston systems are garbage on an AR because the rifle isn't built for it. The AR15 relies on gas entering the BCG and forcing the bolt to unlock and push the bolt carrier back in addition to the backward force of the gas pushing on the carrier. Any AR piston system is only going to give the latter, not the former, which is why you see companies like POF using rollers instead of cam pins on their bolts because of the extra stress that is placed on the bolt.
If you want "ultimate reliability" the answer is still a Kalashnikov variant, but you can still get it to jam if you abuse it.
If you care about gas blowback for suppressors either the PRI gasbuster handle or an adjustable gas block will solve all of your problems.
The only reason why you'd actually want a piston AR is for barrel lengths below 10.5". The Mk18 CQBR is pretty much at the limit of reliability with the DI system because of the incredibly high gas port pressures that mean even subtle differences in dwell time and port size can have dramatic effects on function.
Rifle length gas system is likely to be the softest shooting and most reliable out of all the AR15 gas systems. Port pressure is at its lowest, and as a result dwell time and port size don't have to be controlled as tightly. Mid length and carbine length are going to work just fine though.
A DI rifle is likely to be more accurate as well. A piston system is guaranteed to have more mass hanging off of the barrel than a DI system, which will affect barrel harmonics and reduce accuracy.
If you're obsessive about keeping your rifle clean, just buy an ultrasonic cleaner and drop all the BCG parts into it with water and dish soap after going to the range.
>>28032895
>make my points for me or you're ignorant!
Damn, you're just fucking stupid.
>>28032357
Get a DI. It's what everyone else including the military has ( which is what you want in a SHTF situation). Honestly piston AR's are overrated. If you want a piston operated system then there are plenty of other weapon systems that Pistons are standard for. Pic not really related
>>28032735
If you want ammo that pierce through light cover I recommend the 6.5-7mm range (As I've read in documented ammunition experiments).
>>28032912
No your stupid.
Someone makes a "claim" and while having no knowledge of whether or not it's true you assume it's untrue for some reason and feel the need to make your opinion known instead of thinking to yourself "hmm, I wonder if that's true, maybe I don't know everything about everything" and taking 5 seconds to look it up and possibly expand your knowledge.
>>28032357
I bought a short stroke piston AR because I shoot left handed and I'm tired of every semi-auto I own spitting carbon in my face. I also think it saves some time cleaning since the bolt carrier group doesn't get as dirty, but we're talking minutes out of your day here.
Otherwise, just go with a normal direct-impingement AR and clean it after you shoot. It won't jam on you, you don't need a custom BCG to avoid carrier tilt, and it will put bullets down range where you want them.
>>28032357
>gas piston vs DI thread going?
save yourself the flamewar and shit spewing.
unless you are getting a HK416 or LMT MRP, dont bother with a fuckin piston AR, theyre shit.
notice how the bolt carrier bounces off the carrier retaining pin and buffer tube? after 1000 rounds its galled and beaten to shit.
>>28033037
Yep, carrier tilt is also a major problem with all of these piston systems. Just looking at the AK design you can see how the return spring is directly in line with the piston specifically so carrier tilt doesn't happen.
AR15 piston designs are profoundly pointless outside of extremely rare exceptions.
>>28032725
have you looked at a 7n6 cross section? the steel core is almost 3x the length of a M855. The bullet is also retardedly long due to most of its core being steel and not lead. The bullet is known to tumble almost instantly, basically turning into a piece of shrapnel instead of a icepick.
A piston AR thread and pic related hasn't been posted yet? I see it's been brought up, but come on... You need picture references.
>>28033101
>http://www.calguns.net/calgunforum/showthread.php?t=1118901
OP here.
Sorry, there it is. They have used ones for around 600 on gunbrokers, and I've read a few reviews all saying its a great system.
But, this thread seems to have swayed me in the direction of DI now.
>>28032357
DI was Eugene Stoner's solution to the problems encountered with his multi lug bolt design. everyone said it would not work, he found a solution.
>>28033147
err maybe, i misunderstood your post.
Help me out here.
>>28032524
2/10, see me after class
>>28032643
He's just fucking wrong. It's pure memes
>>28032696
>what is barrier blind ammunition
You're also fucking wrong. And stupid.
>5.45
>not performing incredibly similar to 5.56
>>28032860
And again, using m855 is a shit idea. Barrier blind ammunition, and heavy 75/77 grain loads
>>28032909
That depends entirely on the load, not the caliber.
>>28033037
>>28033086
> Save yourself the shit spewing
> Then goes on to say carrier tilt is still a major problem, and the bolt will show galling after as little as 1000 rounds.
Neither my AA or the Ruger I've handled have any indications of carrier tilt on the buffer or it's extension, and I'd have seen it when cleaning the the Ruger that was over 3 years old and taken to the range regularly. Hell, there's one guy on the site that shall not be named with over 10,000 rounds through his AA with 0 carrier tilt issues whatsoever.
I have no idea how the bolt carrier would gall or peen the carrier retaining pin any harder on a piston system than it would on a DI. If the piston guns are slamming their carrier group rearward with significantly more force than the DIs, I can't tell when I shoot them.
You are both overstating an engineering issue that was solved several years ago with custom bolt carriers.
>>28033403
The problem is that the piston and return spring are not in line with each other.
>>28033403
are you retarded nigger?
unless its a MRP or 416, dont get a piston AR.
its that simple. all the rest have problems because they were not designed correctly, if at all. All they did was swap out the gas tube for a piston, and that shit dont fly in the realm of mechanics.
>>28033477
Yes, but you can prevent tilt by adding metal to the BCG in places to make it ride more snugly in the upper receiver. The Ruger has an enlarged end with rounded lobes, and the AA uses skis.
I'm willing to admit that having proprietary parts and the extra weight for no performance increases means a DI is the better option in 99% of cases, but let's not act like these companies weren't aware of the issue hurting their sales. There's a reason that googling for carrier tilt issues on these rifles shows nearly all results from before 2012.
>>28033548
You sound very angry that I have a different opinion than you. Also I think you may be misinformed. Google image search 'Adams Arms bolt carrier' or 'Ruger SR556 bolt carrier'. They do not look like the carrier groups from a DI gun.
I was looking into a piston AR build. The biggest issue for me is that the parts are somewhat proprietary. There is no mil-spec.
>>28033660
That still doesn't resolve the issue of a force occurring over the bore line, which causes additional muzzle rise.
Carrier tilt isn't the only issue with a piston AR. If people really want a piston AR they should look at a SCAR or Daewoo instead of trying to make the AR15 something it isn't.
I already have a lower. What's the cheapest way to make it into a 16" AR??
>>28032524
>2. A skilled markman can operate a bolt action rifle almost as fast as a semi-automatic one.
>>28033837
> SCAR or Daewoo
Man, I wish. The former is $2000+ for a .223 gun (assuming SCAR-16) when you can get a nice M4-gery for half that price. The latter, well, I'd love one, but I don't see that happening anytime soon.
> Muzzle rise
This isn't an issue for me though. I'm not military. I don't shoot full auto. For follow up shots, I tend to be struggling to keep my aim on something that's running horizontally. Plus, it's a .223 so it still climbs way less than my 7.62x39 gun.
Also, looking at a SCAR diagram, I'm guessing the center of gravity for the bolt carrier is well below it's piston as well. Pic related.
Its a tool. Its not a religion. Its not a wife. Its just a replaceable tool.
There's never going to be a 'happening'. The S will never HTF.
Buy what you want to buy, build what you want to build, and shoot what you want to shoot. Do what makes you happy. If you like shooting, shoot a lot. When your piston or DI system breaks down build or buy a new one.
Don't let little people tell you you're wrong for getting what you want to get. And if you don't like it in the end, sell it, trade it, keep it, whatever. And get a new one and see if you like it better.
>>28033958
>Dat BCG
... The piston looks like a brick.
>>28033958
Right, but at least with the SCAR the return spring is in line with the piston. At any rate, the fact that the SCAR16 has been profoundly unpopular even with SOCOM is really all you need to know.
>>28034271
probably because its ugly
Piston ARs are shit and prone to too many problems.
>>28035003
If ugly was the real problem the SCAR17 and Mk14 EBR wouldn't be in service.
The real issue is that the SCAR16 doesn't do anything the M4/M16 variants can't.
>>28032357
Actually I don't care.
Side Charging master race makes piston irrelevant.
