Gas Piston weight

[Roboss]

So I keep hearing how short stroke and long stroke piston rifles are heavier than direct impingement ones, but how much heavier are they? How much weight do short stroke and long stroke pistons tend to add to a rifle? Like how much does the individual piston system weigh?

[MistWolf]

Gas piston ARs, like the HK416, usually use a heavier profile barrel to deal with heat better. Some also use a heavy handguard. That's where the extra weight comes from.

The actual gas system adds only a couple of ounces to weight.

[mig1nc]

I don't know why, but whenever you look at a manufacturer that offers basically the same gun in both piston and DI versions, the piston one almost always weighs about a pound more.

But I think a bigger aspect is you are putting weight out on the end where you feel it more. Or, more accurately speaking, moving the piston out from inside the bolt carrier forward to the gas block.

If you play golf or tennis think about it like adding weight to the end to increase swing weight.


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[Kyohte]

I’ve come to the conclusion Mistwolf has. It’s less the piston itself and more the other characteristics of the rifle. The LMT NZ reference rifle and Mars-L piston are almost identical in weight. Both are medium profile with a beefy monolithic rail. The LMT barrel sleeve/extension is also heavy.


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[markm]

I don't look at it as the piston adding weight so much as the DI gas tube reduces parts and weight and simplifies operation (in the AR realm anyway).

My thought is... What if you could eliminate those moving parts and replace them with a stainless steel tube???

[Kyohte]

I don't look at it as the piston adding weight so much as the DI gas tube reduces parts and weight and simplifies operation (in the AR realm anyway).

My thought is... What if you could eliminate those moving parts and replace them with a stainless steel tube???

Thread drift here, but why not. Look at this in the reverse. What if we could remove 3 cheap, thin, steel rings and replace them with a sturdier piston? Not advocating for pistons, just tossing up the counter-argument.


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[kyjd75]

Gas piston ARs, like the HK416, usually use a heavier profile barrel to deal with heat better. Some also use a heavy handguard. That's where the extra weight comes from.

The actual gas system adds only a couple of ounces to weight.

This is exactly the answer I was about to post. I have a bunch of Sig 516's, and like the HK 416, they are built like tanks. Lightweight construction was not a consideration for these types of rifles. they are designed for extreme heavy duty use. I do have a Centurion Arms 14.5 P&W that has a heavy barrel and a 12" pictany rail. It is virtually as heavy as my 516's. Most piston guns are simply built to a heavy duty use standard.

[Clint]

Piston rings are not a liability.

They are a more advanced design.

All of the better piston guns FN/HK/Steyr also use piston rings.

This is actually a credit to the design efficiency of the "DI" AR.

Look at this in the reverse.

What if we could remove 3 cheap, thin, steel rings and replace them with a sturdier piston?

Not advocating for pistons, just tossing up the counter-argument.

[Kyohte]

Piston rings are not a liability.

They are a more advanced design.

All of the better piston guns FN/HK/Steyr also use piston rings.

This is actually a credit to the design efficiency of the "DI" AR.

So why don’t older designs need them? Honest question, not trying to be contrarian.


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[lysander]

So why don’t older designs need them? Honest question, not trying to be contrarian.


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Older piston designs usually used a labyrinth seal characterized by groove rings. This is a very effective seal, however it requires length in order to work properly. Sealing rings allow for shorter seal distance. Note the length of the pistons shown above compared the the M14 piston.



Some designs just allowed for leakage and over sized the gas port.