Piston or DI Semiautomatic AR15?

[M118LR]

I'm not a frequent flyer on the AR15 Net due to my opinions on M-4 forgeries etc. So forgive me if I ruffle a few feathers along the way. But I'm attempting to figure out why a piston driven AR that has a stronger recoil curve makes more sense than a DI in a semiautomatic rifle? Now recoil in a 5.56 is a laughing matter, but a 7.62 x 51 coupled with a Magpul stock can induce a little flinch for a novice.

Now we ain't conversing about full automatic real Government AR's, so just stow all that. Yes I'm aware (have experienced) the original troubles with DI M-16's afield. But since my goal is the most accuracy from an AR, isn't the recoil bell curve of a DI more practical in a semiautomatic AR?

Thank You for your input/thoughts/experiences.

 

[Zeroed in]

Can't answer the recoil question, but it can't be that bad. A piston runs way cleaner than DI, in semi or FA.

 

[Jester896]

maybe adding a suppressor to the piston driven will change the curve a little...my piston driven is run with a suppressor exclusively and it is way cleaner than DI

 

[M118LR]

Can't answer the recoil question, but it can't be that bad. A piston runs way cleaner than DI, in semi or FA.

Perhaps the recoil curve is the reason that no Government Agency has attempted to replace a Sniper System Firearm with piston driven system since the M21.

 

[M118LR]

maybe adding a suppressor to the piston driven will change the curve a little...my piston driven is run with a suppressor exclusively and it is way cleaner than DI

A DI with a selectable block suppressed is more finite than a White's gas cutoff.
" The M14 rifle and M60 GPMG use the White expansion and cutoff system to stop (cut off) gas from entering the cylinder once the piston has traveled a short distance.[7] Most systems, however, vent excess gas into the atmosphere through slots, holes, or ports."

Gas-operated reloading - Wikipedia

en.wikipedia.org

But that recoil curve plays an important part at 1K shots with 7.62 x 51 rounds. So why not take advantage of the intrinsic accuracy capability of DI in a semiautomatic only AR? Now I realize that piston driven full automatic firearms are more reliable, but is their anyone alive that can actually drive a semiautomatic at 750 rounds per minute?

 

[SAWMAN]

"Recoil bell curve" is mentioned in the OP.
A primer cracks and ignites the powder charge. Internal pressures rise and propel the bullet down the bbl.
All else being equal,the perceived recoil produced is determined also by length of time that it takes to complete the stated "bell curve".
To me,this IS MORE that influences perceived recoil than the difference between short stroke piston and DI.
YOMV --- SAWMAN

 

[M118LR]

"Recoil bell curve" is mentioned in the OP.
A primer cracks and ignites the powder charge. Internal pressures rise and propel the bullet down the bbl.
All else being equal,the perceived recoil produced is determined also by length of time that it takes to complete the stated "bell curve".
To me,this IS MORE that influences perceived recoil than the difference between short stroke piston and DI.
YOMV --- SAWMAN

Perceived recoil is heavily influenced by the weight of the rifle and butt stock shape/composition. Which are contributors to shooter induced error.

Of note to mechanical accuracy (related to the recoil curve) are Barrel Deflection & Barrel Vibration. Basically a rifle barrel performs like a guitar string while launching a projectile. Barrel rigidity, free- floating parts/mass, and harmonic interplay, are the more influential factors. (To add a little clarity)

Now for the super tech weenies: https://www.scielo.br/j/lajss/a/psL45TjcJXN3yWCpYmrXQxr/?lang=en

For those slightly less tech concerned:
Barrel rigidity effects: https://riflebarrels.com/a-look-at-the-rigidity-of-benchrest-barrels/

Looking at some of the slow motion video's for different systems of gas driven rifles is probably the easiest way to research. There used to be some Old Videos of the M14 and M16 that were pretty graphic as to the amount of barrel deflection & vibration induced by either system. (if someone would like to drop a link I'd appreciate it.) Yet there must be a couple of slow motions of an AR DI and an AR Piston?

 

[stage20]

I'm looking into this myself.
It seems that a long stroke piston AR (Brownells and PWS to name a couple) have more felt recoil, but run more reliable with less carrier tilt.
Short stroke has less recoil.

As far as suppressed, all the posts I've seen, piston AR is louder on the meter, but throws all the gas forward. Maybe not as much noise at the shooters ear.

 

[M118LR]

With all the years of D.I. improvements, is anyone actually still having troubles with semi-automatic (one round per trigger pull) fire of their AR?

"Direct impingement ARs tend to be more accurate at a more affordable price while being easier to carry. On the other hand, piston-driven systems offer more reliability, while running cleaner and cooler."

Direct Impingement vs. Gas Piston: Settling the Debate – Silencer Central

Automatic rifles are incredibly versatile guns, coming in a number of different shapes and sizes. But there are mainly two operating systems that come with this style of firearm…

www.silencercentral.com

 

[Zeroed in]

Perhaps the recoil curve is the reason that no Government Agency has attempted to replace a Sniper System Firearm with piston driven system since the M21.

I doubt it. I would have to think the reason is because of the cost associated in acquiring them, when the DI works just as good, point, pull trigger, Bang.....

 

[M118LR]

I doubt it. I would have to think the reason is because of the cost associated in acquiring them, when the DI works just as good, point, pull trigger, Bang.....

How many Republic Credits have you expended to purchase an FNSCAR?
https://www.americanspecialops.com/special-ops-weapons/mk-20-mod-0-ssr.php
Is this just another failed attempt to replace the Knights Armament SR-15?
Neither of which have been as capable as the bolt action M40 or Semiautomatic M21. ????

 

[Zeroed in]

How many Republic Credits have you expended to purchase an FNSCAR?
https://www.americanspecialops.com/special-ops-weapons/mk-20-mod-0-ssr.php
Is this just another failed attempt to replace the Knights Armament SR-15?
Neither of which have been as capable as the bolt action M40 or Semiautomatic M21. ????

I don't want one, so None.

 

[M118LR]

I don't want one, so None.

Uncle Sam will spend some BIG BUCKS, but Big Green seems to be the most Miserly of the children. Perhaps that's in part of holding such large amounts of firearms? Tier One Combatants seem to get more of the expensive toys, regardless of which branch. JMHO.

 

[oneshot]

Have played with this since the 70.s one thing every one seems to forget is the ar- 15 systems bolt was not designed to work with a piston, this creates other issues to deal with and more maintenance . more barrel whip is one, how meanly shoots enough rounds to worrier about bolt heat, and the barrel heat will be the same. You should see a slow motion high speed video pit of a AK- barrel being fired and a AR- barrel being fired with piston and DI from my exp. I had more recoil plus it adds more weight. And for those that say it works in a AK. but AK bolt is a different lock up and release and how meanly target shoots use a AK, Now to the ones that will through the M-14 at me , the look at the way the bolt works, it cams and is then pushed straight back, and the rec. is a hell of meat to it and the barrel system is a lot stronger , but the barrel on it still has a lot of whip to it . Just something for to think on. Just my 5 cents jj

 

[M118LR]

So it looks like it's time to give this a bottom line.
While I'm not sure if the short or long action piston 5.56 is the best answer to the 300 yard mag dump equation, it appears that Spec Ops has found a favorite in the HK offering. When it comes to drawing the most out of a .223/5.56 on the 600 yard range a 20 inch heavy barreled DI appears to be the proper answer. Now to take advantage of the distance available with a 7.62 x 51 a DI 22 inch or longer heavy barreled AR seems to be the target, but standardization seems to be problematic. Which lower you select may have distinct influence on the overall abilities. Can't even standardize the mag-well, some are still based on the FN/FAL mag. Does this sound about right? Or have I delved deeper into the abyss?

 

[BowChamp]

Let's just say I have........one DI operated ar15...and I've had exactly 0 problems with them.....I mean it. LOL!!!

Wouldn't change a thing!!!

 

[Rebel_Rider1969]

Have played with this since the 70.s one thing every one seems to forget is the ar- 15 systems bolt was not designed to work with a piston, this creates other issues to deal with and more maintenance . more barrel whip is one, how meanly shoots enough rounds to worrier about bolt heat, and the barrel heat will be the same. You should see a slow motion high speed video pit of a AK- barrel being fired and a AR- barrel being fired with piston and DI from my exp. I had more recoil plus it adds more weight. And for those that say it works in a AK. but AK bolt is a different lock up and release and how meanly target shoots use a AK, Now to the ones that will through the M-14 at me , the look at the way the bolt works, it cams and is then pushed straight back, and the rec. is a hell of meat to it and the barrel system is a lot stronger , but the barrel on it still has a lot of whip to it . Just something for to think on. Just my 5 cents jj

This explains the loss of accuracy on the bullpups I'm guessing.

 

[Raven]

Have played with this since the 70.s one thing every one seems to forget is the ar- 15 systems bolt was not designed to work with a piston, this creates other issues to deal with and more maintenance . more barrel whip is one, how meanly shoots enough rounds to worrier about bolt heat, and the barrel heat will be the same. You should see a slow motion high speed video pit of a AK- barrel being fired and a AR- barrel being fired with piston and DI from my exp. I had more recoil plus it adds more weight. And for those that say it works in a AK. but AK bolt is a different lock up and release and how meanly target shoots use a AK, Now to the ones that will through the M-14 at me , the look at the way the bolt works, it cams and is then pushed straight back, and the rec. is a hell of meat to it and the barrel system is a lot stronger , but the barrel on it still has a lot of whip to it . Just something for to think on. Just my 5 cents jj

Whip it good! I've seen the AK slow motion video

 

[Raven]

This explains the loss of accuracy on the bullpups I'm guessing.

That's all trigger right there

 

[M118LR]

It seems like the bottom line is actually the bottom line to my way of thinking. Any objections?