I’m not trying solve a problem... just understand the relationships. And be more educated and understand firearm design choices better.
I think this is well understood enough that there should be no surprises when things change. So I disagree that you may get unexpected results. The results should be very predictable based on how much study has been invested in this area
Ah, I see. Makes sense. Although, in my experience, when it comes to complex interactions between different materials, chemistry and physics, you should always be prepared for unexpected results.
Can you correctly predict whether the glass marble will break upon impact with each of the target materials shown?
https://www.youtube.com/watch?v=txqftpAhwks
As the owner of a WK180-C which was designed as a NR firearm with a 18.5” barrel I find the choice of a carbine length gas system, a curious choice. I actually spoke to someone today at Kodiak Defence and what I came away with is that they opted for ultimate reliability with any ammo and were not really concerned with over gassing as the piston system is self regulating, in that it vents the gas, instantly reducing pressure once the piston moves through venting holes in the gas block. So once the piston has moved enough to cycle the action, any and all additional pressure is vented. So having a carbine length gas system with an oversized gas port provides plenty of gas to cycle the action without concerns of over gassing.[/QUOTE]
Overgassing isn't a problem of too much gas. Overgassing is when something goes wrong in the sequence of firing because there is too much gas. Excessive peak pressure hitting the piston too fast can crack the piston. A stronger piston can mitigate. It can cause the action to attempt to extract the case before the case has released from the chamber wall, lengthening the gas system can mitigate. it can cause a stiff extractor to tear the rim off the case, changing extractor geometer and spring tension can mitigate. And so on. Its a complex system, and when you start using blunt adjustments like gas volume and system length, it can be very difficult to predict where the first issue will appear. Its also hard to predict, given all of the variables, how much gas is too much gas. Eventually you just have to build it and test it and see what happens.
Does a piston system move slower than a Direct Impingement? I've never looked into that. If so, than yes that would be more tolerant to excessive gas without seeing any of those other issues.
How much velocity does a bullet loose, at the muzzle, in a carbine gas vs rifle gas given the same barrel length?
Say a stag 10 with both rifle length gas, how much does a 20" barrel lose over a 22" and 24"? (6.5cm)
Those are two different questions.
Same barrel length, and only change is moving the gas port, the muzzle velocity probably won't be much different. unless you are using super precise ammo I would predict that you'd barely be able to measure the difference. There is probably more variation between barrels of identical manufacture just due to normal tolerances than there is between barrels of the same length and different gas ports.
You might see a difference at the extreme end between pistol length and rifle length, but you probably won't even find many 20" long barrels with a pistol length system to test.
To test this well what you would want to do is get 3 custom barrels and drill gas ports at each location on each barrel, block all the ports but rifle and shoot them all to take the average, then plug rifle open mid, repeat, etc, for each. Average the velocities across the barrels. This way you will have velocity date for each port with the same barrel, so variations in chamber etc are consistent. It would be interesting to see. I doubt there would be much spread, but if there is, pistol will be the most extreme.
As for your second question, barrel length is barrel length, different rules of thumb predict between 25-100 fps per inch. But thats non linear. Adding an inch to a 4 inch barrel is not the same as adding an inch to a 30" barrel.
