Honest Question: Mid-Length vs Carbine Length Gas Systems?

[LivingtheHistoryM1]

I realize I may be opening a can of worms, but I wanted to gauge how much of a practical difference there is between the carbine and mid-length gas systems on a 16 inch barrel, provided they are gassed and buffered correctly. Additionally, has anyone witnessed a significant difference in lifespan on components between a carbine and a mid-length gas system? Is that something that I should worry about, given that my annual round count would be in the hundreds, not thousands?
Looking to assemble a new upper, so any practical answers would be helpful.

[vicious_cb]

I realize I may be opening a can of worms, but I wanted to gauge how much of a practical difference there is between the carbine and mid-length gas systems on a 16 inch barrel, provided they are gassed and buffered correctly. Additionally, has anyone witnessed a significant difference in lifespan on components between a carbine and a mid-length gas system? Is that something that I should worry about, given that my annual round count would be in the hundreds, not thousands?
Looking to assemble a new upper, so any practical answers would be helpful.

Contrary to popular belief on the internet, I have seen no significant difference between properly gased car gas length systems and mid lengths. Maybe a some of my smaller gas port midlengths shoot a tiny bit smoother but you probably wouldnt notice the difference unless you were doing a back to back comparison.

Basically I shot out all my 16" car barrels from S&W to Colt and one 14.5" LMT car M4 style barrel that I built in the early to mid 2000's and replaced them all with midlengths, and I have noticed basically nothing in terms of real world shootability, durability or parts life.

[Uncas47]

Contrary to popular belief on the internet, I have seen no significant difference between properly gased car gas length systems and mid lengths. Maybe a some of my smaller gas port midlengths shoot a tiny bit smoother but you probably wouldnt notice the difference unless you were doing a back to back comparison.

Basically I shot out all my 16" car barrels from S&W to Colt and one 14.5" LMT car M4 style barrel that I built in the early to mid 2000's and replaced them all with midlengths, and I have noticed basically nothing in terms of real world shootability, durability or parts life.

Easily the most honest assessment I've ever read.

[markm]

For 16" barrel length, the reduced port pressure on a middy is real. I shoot almost all 14.5 carbine gas right now... so I'm not a middy fan boy or anything. But if I was selecting a 16" barrel and didn't require the forged FSB, I'd go with mid-length.

On my 14.5s... mid-length vs. carbine is dramatic. But there's port sizes at play there. An .080" port middy will feel really close to a carbine in recoil impulse, but an .076" port middy will really smooth out recoil.

[MarshallDodge]

What about intermediate length?

I prefer midlength, and have been running BCM and Sabre Defense carbines in middy configuration for almost 15 years without an issue- cold or hot, dirty or clean. I still have a carbine length upper and shoot it from time to time. The middy is noticeably smoother.

[npena84]

https://soldiersystems.net/2018/05/1...d-performance/

Excited shoot this 6960 upper I just purchased, gas port on the Google chart is .71, curious to see how it shoots compared to my DD mid length

[titsonritz]

My SIONICS 16” mid length w/ an A5 RE is noticeably smoother than my Colt 6920. Now how much that translates into practical shootability and parts wear reduction I couldn’t say, that said I’ll pick a mid length gas system every time on 16” if building a gun for myself but I still have multiple 6920 barrels on hand for replacement parts.

[mack7.62]

I thought Crane already answered this.

pdf of test results

chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://partner-mco-archive.s3.amazonaws.com/client_files/1527866983.pdf



NSWC-Crane Mid-Length Gas System Testing Shows Increased Performance & Service Life For M4 Carbines

https://soldiersystems.net/2018/05/1...d-performance/

So far, Crane has put 30,400 rounds of M855A1 through three M4A1s equipped with 14.5″ cold hammer forged barrels and a mid-gas system with a gas block approximately 9.8″ from the bolt face.

They stated SOF M4A1s normally start to see accuracy degradation at around 6,000 rounds. But during testing of the mid-gas system, they’d hit 12,600 and still hadn’t seen any changes.

They also have only broken one bolt so far in testing, although I don’t think they’re ready to attribute the improved bolt performance to the mid-gas system.

The Crane team will finish testing up with 34,000 rounds per upper. It’s not that they don’t think the barrels can’t take more, but rather that they had to use the same lot of M855A1 to satisfy the accuracy portions.

Conclusion

Although testing to 34,000 rounds isn’t yet complete, the conclusion is simple. Use of a mid-gas system significantly extends the life of the overall weapon system. It also offers increased performance over a carbine-length gas system.

[grizzman]

I find it very hard to believe that a change in gas system would consistently increase barrel life. Throat erosion has absolutely no correlation with what occurs when the gas reaches the bolt carrier.

An increase in bolt life is completely reasonable. but it's not like bolt breakage is common.

[Todd.K]

I can absolutely tell the difference shooting carbine and mid, but it’s minimal. And I’ll admit I’m not the average user, I’m much more aware of how any AR is shooting without even thinking about it.

Nobody thinks about gas port erosion, because you don’t see it, but it happens faster the closer to the chamber the port is. That’s a lot of ammo to burn through before you find a difference, and the cost of that makes the cost of a barrel replacement pretty insignificant.

I prefer mid, but I’d choose barrel quality over gas system and not think about it again. Unless it’s a FSB build, I will not be cramped on a carbine handguard again.