Question(s) about dwell time

[JG007]

I have a basic understanding of it, and the bcm explanation of going 11.5 instead of 10.5 is often posted.

But, if dwell time is a concern on the 10.5

-would using the lmt enhanced carrier improve reliability by increasing dwell time ?

-would the vltor A5 buffer have an even greater benefit than normal?


-does the reduced dwell concern apply to models like the 14.5 KAC with intermediate gas?

-what about a specialty muzzle device, didn't vltor have something like that on a 9" rifle?

[tb-av]

Read the thread about the 11.5" build. I asked that same question. There are many areas of 'dwell' . One area is bullet from gas block to muzzle... another is the action of the bolt carrier.

It was explained to me the enhanced carrier affords the brass time to contract a bit an extract better. So the carrier is 'dwelling' for one reason or one desired action... at the same time the bullet may be 'dwelling' between gas block and muzzle for another desired result.

I suppose the burn speed of the powder would create a 'dwell' from chamber to gas block as well.

I somewhat guessing here... but I had the same question. I think it's one of those things where every change is an impact or a compromise on the entire system.

[tom12.7]

In this reference, dwell is just a time measurement or comparison in time.
Looking at systems specifically for the components mentioned. The LMT enhanced carrier does delay in time unlocking and extraction over a standard carrier. The A5 or rifle like action system does delay time in comparison to an equivalent carbine system, due to its reduced cyclic rate.
What can both do? The delay in time allows both to operate in a span of reduced stresses and strains due the delay allowing residual pressures to drop to lower levels. That means less work the system needs to do to function within its span of use.
What are the cons of the systems? The LMT enhanced carrier works with reduced pressures, it adds durability, but sacrifices reliability on its own, it can hyper cycle, or cycle too quickly for reliable use. The properly gassed conventional system now becomes over gassed with the LMT enhanced carrier and issues arise. With the A5 or rifle like action system, a larger mass action than conventional could be required for proper operation.
When adding the two systems together, you could tend to get reliable function in a larger range with with a dedicated port that is smaller than what is conventional. If a fixed gas port runs in its span a 20", 14.5", 10.5", or whatever with a LMT enhanced A5H4 without a can, it's gassed pretty hard. If that same example runs similar with standard A5H2, it can run well with more mass if a can could be involved.
Adding these attributes to a 14.5" mid gas, or KAC 16" intermediate gas system can be icing on the cake, with proper porting. The delay in time can further reduce operating pressures and work required. Dedicated porting with the LMT/A5 combo in those can have great results in their operating span.

[ClassIIIGunsmith]

Continuing from the others. The only thing not mentioned is the dwell time for the case extraction is important if you don't want split, sheared, snapped rims, and or ruptured cases from extraction with high chamber pressure. Solution for that issue if you can't work with the gas system, is fluting the chamber like the Hk delayed roller-locks of the MP5,G3, Hk91,92,93,94, and clones. But I have never seen a AR with H.C.P.E except when McNamara changed the powder on the M16.

[JG007]

Two questions,

Is extending the system, on both ends, always better? Extending the gas tube/port, and the A5 buffer?


When is the lmt carrier beneficial vs detrimental? Only when the vltor A5 buffer is used with as heavy a buffer as possible?

My 11.5 chf bcm has an A5H4, enhanced carrier, and green springco spring.

I have a custom cut, small ported upper enroute with np3 standard bcg

[tom12.7]

A properly weighted and sprung rifle or rifle like A5 action system is preferable in terms of function over a carbine like action system.
Extending the port locations is not always preferable, but in some cases it is, just depends on the particular situation.
The LMT enhanced carrier works well as long as you keep the speed in check. If the porting properly uses the enhanced carrier with an A5H1-A5H4, it can run well. An example of a poor application would be a port that could use a carbine H3, but instead a 3.0 ounce buffer is used.
The BCM combo listed works well without a can. I would tend to prefer a smaller port for suppressor applications. That way a lighter buffer may be used without a can and a heavier buffer with it, both properly used for each role.

[JG007]

Am I the only one that looks at a gas system like a carburetor? (im sure there is likely some technical flaw in the analogy), and if so would a suppressor be like a reverse supercharger?

*I am not an engineer

[MistWolf]

Carburetors mix and meter air & fuel. The gas system of the AR is a pneumatic system wherein it converts pressurized gas into mechanical motion.

The suppressor is not a supercharger. Superchargers use positive displacement to compress gas to a higher pressure. A suppressor is nothing more than an expensive muffler