Long stroke SureFire Carrier

[tom12.7]

To avoid most patch works, the lower needs alterations as well. Gun bans zones stifle innovation. Until there is a market with demand, there's little reason to provide the option, from a manufacturing standpoint.
Some of this was plain to see when I was introduced into this, but after a generation of time in that, little has changed for the demand side except for some requests that ended up with patches more than fixes. The idea of an updated base concept was proven a long time ago.

[Diamondback]

Frankly, if for no other reason than sheer curiosity I'd like to see what an unfettered by cost or law Full Metal Sullivan rework from muzzle to recoil pad would look like...

[tom12.7]

There is a lot that could be looked at long before my introduction to the system. The exhaust events for the debris hole and carrier key is one major example. The comparison with the constant volume Vs the swept volume inside the carrier with expansion ratios with the resultant condensates. There is a lot more, but most of that isn't open information beyond that

[mig1nc]

There is a lot that could be looked at long before my introduction to the system. The exhaust events for the debris hole and carrier key is one major example. The comparison with the constant volume Vs the swept volume inside the carrier with expansion ratios with the resultant condensates. There is a lot more, but most of that isn't open information beyond that

That's a really neat idea. No doubt the volume of the AR-15 internal piston was designed to match the original M16 rifle, yes?

[MistWolf]

Timing still matters.

Of course timing still matters. But if the gas port is right, the buffer weight is right and the spring is right, the timing is right.

All that aside, my point is, an AR isn't over gassed just because it has a carbine gas system

[BufordTJustice]

There's some better options on the table if we are open to making some base changes to the receivers. That's when we can really see more of the gains without so many losses. It will require a demand for that, there's no reason to make it without a market for it.

Agreed.

Tom, I know you remember the original position of the gas tube and gas key on the AR10; it was lower profile and on the side of the BCG, not the top.

I think the market is ready for the change.

Lengthen lug bolts with some LMT style radiuses at the lug roots, etc.

In vulgar terms, I wish this and the LMT e-carrier had a baby. Because there are some features of each i would prefer to have, and vice versa.

However, going back to my original point, reengineering the gas key/gas tube geometry would permit a shortening of the overall length of the carrier, INCREASING stroke length without increasing OAL of the weapon.

Put a witness Mark on the side of the carrier to show how far it should be retracted in order to break the weapon open. And use tungsten inserts in the carrier to increase mass density. Adding even 25mm to the overall stroke of the carrier completely changes the ballgame.

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[mig1nc]

There is a lot that could be looked at long before my introduction to the system. The exhaust events for the debris hole and carrier key is one major example. The comparison with the constant volume Vs the swept volume inside the carrier with expansion ratios with the resultant condensates. There is a lot more, but most of that isn't open information beyond that

Tom, if I'm understanding your comment about constant volume vs swept volume vis-à-vis carrier volume, what is your opinion in the use case of a suppressed SBR where total operating system volume of say a 10.5" barrel with a 6-7" silencer would have volume akin to a long barrel rifle, then leveraging something like the PRI Fat Boy gas tube to increase gas tube volume to more closely match rifle length gas tube volume? Would that bring you back into rifle-like balance with traditional carrier volume?

Sorry if this writing doesn't make sense, I'm fighting off a head cold at the moment.

[Diamondback]

However, going back to my original point, reengineering the gas key/gas tube geometry would permit a shortening of the overall length of the carrier, INCREASING stroke length without increasing OAL of the weapon.

Put a witness Mark on the side of the carrier to show how far it should be retracted in order to break the weapon open. And use tungsten inserts in the carrier to increase mass density. Adding even 25mm to the overall stroke of the carrier completely changes the ballgame.

Another question would be effects for Single Shot vs Full Auto--am I correct in thinking that Semi needing a cyclic rate just slow enough that the mag-spring and follower can pop the bolt hold-open before the carrier returns to BHO position is a different and lower demand threshold than a Burst or Full Mag Dump? (Example, when I mentioned that I was planning on using his Crane-spec 10.3 in an unsuppressed pistol rather than a suppressed SBR, Jason at Andro Corp was very specific in giving me a headsup that the barrel was designed for suppressed use and I would need to tinker at the back end to slow the cyclic rate for BHO-pop, though it'd still go bang every time if the FCG and BCG did their parts.)

[tom12.7]

There may be some confusion here.
For any given normal DI base AR there are some certain events that occur within certain time frames. Before the gas seal at the base sealing edge of the bullet enters into the gas port area of the barrel, the barrel's gas port and gas system has little exposure to any appreciable pressure. At the points where the high pressure gasses behind that bullet seal interacts directly with that barrel port, those moments are the points of time for the highest exposed barrel pressure to that port. The gas system does not immediately pressurize at that point, that is the time that highest pressure is introduced to it. As the bullet passes past the port, the base bore pressure decreases, still high but rapidly descending in pressure. When the barrel uncorks from the barrel, the pressure does not instantly drop down to ambient, it takes time to blow it out.
As far as the gas and action system, since it is behind an orifice (gas port) it takes time for it to build pressure. With trying to keep this simple. If you superimpose the pressure events for both the barrel and in the gas system, you get a large barrel pressure curve and a much smaller action and gas system pressure curve that is delayed in time to the barrel pressure. The action and gas system combined have a constant volume to fill while fully in battery. As the system begins to operate and the carrier moves, there is a swept volume, the area between the bolt and carrier and the key to the gas tube. The swept volume increases until we enter the exhaust events. If done right, the vast majority of gasses exits out the exhaust porting before the gas key interface to the tube opens, similar with the debris hole and bolt tail.
This is about as basic as I can go for operation, but with the intent continuing some of this later. Sure this assumes that pv=k, Jr. high pv=nrt does explain it more accurately. But some of this could be much further looked into than this knowing that nothing seals 100% and there can be different gasses and condensates present. My main emphasis is timing, as in how to increase efficiencies using that to translate into fewer issues rather than run into base issues.
Sorry for trying to make some of this overly basic, but I don't want to lose people.
Would anyone like to look deeper into some things?

[Clint]

Of course timing still matters. But if the gas port is right, the buffer weight is right and the spring is right, the timing is right.

The overall gas drive (total area under the PV curve) can be made right by adjusting the gas port size, but that is not the same thing as optimal timing.

Gas port location is the most important factor controlling the timing.

Why do 14.5" carbines break more bolts than rifles?
TIMING

All that aside, my point is, an AR isn't over gassed just because it has a carbine gas system

Agreed, but that doesn't mean a 16" carbine is the optimal configuration.