WK and MCR op rod and gas tube length and parts wear and tear

[Ustauk]

Watching the latest Grand Thumb video, the presenter makes a note how the shorter length of travel on a 10.5" AR-15 with a short length gas port increases the wear on parts of that rifle versus other AR-15s with longer gas port lengths. Looking at the original AR-180 on a takedown video, the gas port and piston look either mid-length or rifle length. Is it possible that both the WK and MCR would have less problems with parts breakage and fasteners loosening if they used a mid or rifle length op rod and gas port? Can anyone with a longer op rod/gas tube on their rare RWA 180 comment on how its parts and fasteners held up? Thanks!

 

[Blastattack]

They probably would far better. I have absolutely no idea why they decided that carbine gas on a rifle-length barrel was a good idea.

 

[Bratwurst]

They probably would far better. I have absolutely no idea why they decided that carbine gas on a rifle-length barrel was a good idea.

Because it works with just about every type of ammo. They have to consider that we'll put "speshul handloads" or "bargain bucket" ammo through them then loudly complain all over the internet if it doesn't provide 110% reliability.

Nearly 3 years on people are still posting threads about broken pistons or receiver wear concerns (ie. They have heard about but not actually seen them) even though the issues were always fixed promptly, spare parts were widely available and the latter was never an issue.

Never forget that in the internet age your firearm is only as good as a fat man with no combat/policing experience and an over inflated ego decides it is.

 

[greentips]

I don't think the gas port distance matters for push rod system as much as DI , SCAR, MCX and HK416 don't have far gas port. SCAR is the most durable system out there. In fact, SCAR has a pretty short push rod, the bolt carrier has a long extension - the complete opposite to AR.

Push rod system has a very small gas volume compared to DI. DI has a long and voluminous path for the pressurized gas. The push rod works as an intermediate between the gas the bolt, but DI is missing the intermediate. In push rod system, the unlocking is determined by the force imparted by the push rod that is regulated by both volumetric flow and the push rod spring rate, versus DI is directly and only control by volumetric flow. That is why it is more difficult to mitigate fast unlocking time and then bolt velocity in DI once the gas port pressure is getting high - there isn't an intermediate between the gas block and the bolt.

 

[Ustauk]

Thanks for the info; I wasn't sure if the same effect would be apparent for pistons, and it appears the consensus is no. Fair enough, and thanks!

Is there a reason the piston system fasteners on other piston guns don't need to be Loc-tited down like the ones in both Canadian 180s?

 

[AlexF]

One important comment about Garand Thumb's video: in it, he talks about manufactures which must over-gas DI rifles because of steel case ammo, reloads and non milspec ammo.
If you want reliability, stick to as few combinations of firearm, magazine and ammunition as possible.
Some very reliably magazines were banned by the US Army because they were extremely reliable in some firearms and caused massive headaches in others!

 

[beltfed]

The biggest difference I see is if they had gone with a standard rifle length gas system, owners could use off the shelf AR rifle barrels, making upgrades to quality match barrels and different calibers much easier.
They could have designed for different gas settings as well with an upgraded gas regulator/plug/block.

All at increases in costs of course which did not fit the original mandate, nor work with the environment where several non-restricted alternatives existed to make the exercise unlikely to be successful.....however, the landscape has significantly changed, so maybe someone could tool up and start making improvements through kits?
If they can make a steel upper and 9mm blowback conversions, this seems a logical progression.

 

[Ustauk]

The video could have more relevance when producing build using the Jard J180, should Sylvestre Sporting Goods manage to successfully distribute the build kit (last ETA was late July, but that was push back from an earlier ETA, so who knows). That design uses an AR15 gas tube to directly impinge gas against an AR180 style bolt control group, riding AR180 style guide rods, recoiling against AR180 style springs. A short length of travel if using a carbine length gas tube with the J180 could cause similar issues to that of shorter barreled AR15s, though a tunable gas block may help with that.

I suspect this theory won't be tested much; its more likely people will want to throw a non-restricted a barrel on the J180, allowing ready use of mid or rifle length gas tubes and barrels with matching port lengths, and also granting the advantages of using said barrels with 556 noted in the video. I could be wrong, and everyone will want a short barrel restricted J180, but I guess we'll see, should the firearm ever grace our shores. Only time will tell.

 

[Ustauk]

The video could have more relevance when producing build using the Jard J180, should Sylvestre Sporting Goods manage to successfully distribute the build kit (last ETA was late July, but that was push back from an earlier ETA, so who knows). That design uses an AR15 gas tube to directly impinge gas against an AR180 style bolt control group, riding AR180 style guide rods, recoiling against AR180 style springs. A short length of travel if using a carbine length gas tube with the J180 could cause similar issues to that of shorter barreled AR15s, though a tunable gas block may help with that.

I suspect this theory won't be tested much; its more likely people will want to throw a non-restricted a barrel on the J180, allowing ready use of mid or rifle length gas tubes and barrels with matching port lengths, and also granting the advantages of using said barrels with 556 noted in the video. I could be wrong, and everyone will want a short barrel restricted J180, but I guess we'll see, should the firearm ever grace our shores. Only time will tell.