boyntonstu wrote:Assume that they are identical in performance.
the question. Are they?
What else would you consider before choosing?
Let's be honest - I wouldn't normally choose to build a coaxial.
I do quite like the ability to swap barrel lengths practically and don't need the space saving of a coaxial. Still, NONE of that is related to actual ballistic performance.
I believe that a barrel sealing piston is smaller, lighter, and easier to make than a coaxial piston.
...um, no. A barrel sealing needs the extra length to extend over the chamber port to the sealing face, and a coaxial piston doesn't.
A coaxial piston can inherently be lighter and smaller than a barrel sealing piston.
In addition, I would prefer to be behind the breech than in front of the muzzle.
While a reasonable point about muzzle loading, if you're working on a load before pressurisation sequence, there's no extra danger to the user.
Given the not unknown possibility for sealing faces to detach from the piston*, pressurizing before loading is a potential danger even with a barrel-sealing breech-loader.*Not to mention that compressed air at the kind of velocity it leaves a valve is not exactly safe either!
Anyway, coaxials CAN be breech-loaded, they just aren't normally built that way.
I've got a set of plans for a piston valve coaxial which can be breech-loaded. haven't really much drive to build it, but it would certainly work if I did.
Gippeto wrote:Stu did a tee piston and Rag did a co-ax with equal properties....review to find the answer to your question.
Bear in mind, those are simulated with rough parameters. I don't have the potential to generate flow coefficients in a heartbeat.
Also, as I have already said, the Trom-Boyn is inherently hindered by its sub-calibre valve.
My point was more to demonstrate that the Trom-Boyn wasn't a sterling example of a barrel sealer and that coaxials weren't automatically hindered by their design.
What I have done doesn't prove anything of how a well design coaxial and a well designed barrel sealer would compare to one another. My guess is the difference is pretty insignificant.
tghhs wrote:I also believe that this would create a more laminar flow for the air.
Depends. While it improves valve-to-barrel flow, it will inhibit chamber-to-valve flow.
While normally, V-2-B flow is the more limited, and thus worth trading C-2-V flow for, you will need to bear in mind that there is a point where taking it too far will start to undo the gains accrued.