Thoughts on Piston Driven AR's

[will_1400]

Aren't the problems associated with excessive chamber heat in DI ARs caused mainly by people using an AR like an LMG instead of a rifle?

[Failure2Stop]

Aren't the problems associated with excessive chamber heat in DI ARs caused mainly by people using an AR like an LMG instead of a rifle?

That's the point of the IAR.
Feels like an M4, puts out a lot more lead.
Lots of ways to contribute to the success of that application, but weight reduction is not one of those.

I have shot M4s to the point that they had cook-offs.
6 mags in less than 5 minutes will get you there.
Drop that to 4 mags in the same time and you will be ok (non-SOCOM thickness barrel).

IARs will push more, and the op system helps, but it isn't the only factor.
There is also a change in application. The IAR is not an LMG, its an Automatic Rifle, and it has to be shot as such.

[will_1400]

Gotcha. Thanks for the explanation.

[jslaker]

The fact that two Colt submissions (both DI) made it to the final cut on the IAR selection prettty much killed the argument in my opinion.
Piston systems do not appreciably drop chamber temperature below DI systems, the real cause of cook-offs.
The IAR was chosen due to it's performance in relation to a needs document, not because of its operating system. It is significantly different than an M16/M4 in many more areas than just operating system, and all of those changes contribute to its success where others failed.

I was honestly thinking more gas tube than chamber temp.

ETA:

FWIW, it's my honest suspicion that the HK416 was chosen for the IAR because someone in the Marines wanted a backdoor way to field HK416s than any inherent advantage to the piston system anyway.

[Jay Cunningham]

FWIW, it's my honest suspicion that the HK416 was chosen for the IAR because someone in the Marines wanted a backdoor way to field HK416s than any inherent advantage to the piston system anyway.

I think maybe F2S has slightly more insight into this than his honest suspicion.

Um... yeah.

[LittleLebowski]

I think maybe F2S has slightly more insight into this than his honest suspicion.

Um... yeah.

Yup. Which is why he's an SME here. Folks, listen to him when he speaks.

[Failure2Stop]

FWIW, it's my honest suspicion that the HK416 was chosen for the IAR because someone in the Marines wanted a backdoor way to field HK416s than any inherent advantage to the piston system anyway.

It's my "strong suspicion" that the IAR was a way to give a more appropriate platform to users when the only official option was the M16A4, which is only slightly more cumbersome than a fence post and is neutered by 3-round burst.

[fuse]

It's my "strong suspicion" that the IAR was a way to give a more appropriate platform to users when the only official option was the M16A4, which is only slightly more cumbersome than a fence post and is neutered by 3-round burst.

Interesting to hear that full auto is acceptable, again.

Perhaps we're in for a new era of spray and pray, with awesome new hardware that can keep up?

[DocGKR]

"Perhaps we're in for a new era of spray and pray, with awesome new hardware that can keep up?"

Or perhaps we are in for an era of well trained and qualified individuals who know when and how to properly use full auto fire...

[will_1400]

IIRC, "spray and pray" was the standard approach when the Army adopted the M16 back in the 60's, the philosophy being that if you put enough fire downrange, you're bound to hit something eventually.