Quote from: Sbak on June 27, 2020, 08:39:03 PMQuote from: mackeral5 on June 27, 2020, 07:19:46 PMI assume with your port specs you are planning an unregulated build. With the relatively short barrel length and 300cc tank a free breathing, regulated Cobra valve would really shine at your desired power levels. I would venture to say this combination would be capable of yielding more shots within 4% or less ES than unregulated. But this is coming from someone who doesn't have a significant amount of experience with unregulated tunes....You may be right, it would be slightly more efficient, but would have less overall capacity. Not really sure which one would yield more shots.That being said, I'm not the regulated type of guy. A reliable, well tuned, unregulated pcp is more my style. Plus I will be making another bolt and barrel combo for this down the line to shoot my .250 bullet I designed (if I enjoy the bullpup style that is) and at 52 grains I'll need all the plenum and porting I can get. I don't want to have to open the valve throat any more than it is. At .20 porting I should be able to shoot the 52gr .250 at 950 fps unregulatedThere are many ways to skin a cat, again I am looking forward to following along with yours. I spent a brief period of time pursuing a similar unregulated .357 Bulldog tune but ultimately went regulated. My guess is porting was already too large from the factory to yield flat enough of a shot string at lower power. Some day I may experiment with strangling the transfer a bit more....
Quote from: mackeral5 on June 27, 2020, 07:19:46 PMI assume with your port specs you are planning an unregulated build. With the relatively short barrel length and 300cc tank a free breathing, regulated Cobra valve would really shine at your desired power levels. I would venture to say this combination would be capable of yielding more shots within 4% or less ES than unregulated. But this is coming from someone who doesn't have a significant amount of experience with unregulated tunes....You may be right, it would be slightly more efficient, but would have less overall capacity. Not really sure which one would yield more shots.That being said, I'm not the regulated type of guy. A reliable, well tuned, unregulated pcp is more my style. Plus I will be making another bolt and barrel combo for this down the line to shoot my .250 bullet I designed (if I enjoy the bullpup style that is) and at 52 grains I'll need all the plenum and porting I can get. I don't want to have to open the valve throat any more than it is. At .20 porting I should be able to shoot the 52gr .250 at 950 fps unregulated
I assume with your port specs you are planning an unregulated build. With the relatively short barrel length and 300cc tank a free breathing, regulated Cobra valve would really shine at your desired power levels. I would venture to say this combination would be capable of yielding more shots within 4% or less ES than unregulated. But this is coming from someone who doesn't have a significant amount of experience with unregulated tunes....
Impressed Shane. I couldn't make poppets like that on a lathe let alone a drill press! Smart choice of platform. That air tube looks huge!
I got the barrel port done, minus a little smoothing on the interior edges, and also the port on the probe. I drilled and tapped two 8-32 barrel anchor points to hold the barrel. The barrel to breach is a metal to metal contact with no oring sealing so i would like a little "squish" to help minimize any leaking. Also, got the .50 OD barrel sleeved with 13mm ID 15mm OD carbon tubing. Since the barrel is short and the towers act like barrel bands, the carbon fiber wont be doing much stiffening. It was just a convenient way to increase the barrel OD back to 15mm to fit in the towers. Also, CF looks cool
Shane , that is an absolutely great tune with excellent efficiency. I’m gathering parts to build a sub 500 fps pistol to shoot the .357 pellets from JSB . I’ve found that even a .25 cal pellet will completely pass through a partridge breast at 450 fps. The 357 should come to a stop much sooner. Please post some pics of the accuracy.