Getting 50 more FPS in a 1720T pistol?

[doninva]

My 1720T field target pistol is shooting 730FPS with 8.4 JSBs. I have a JDS regulated 13CI tank so air is not an issue but I can't seem to get the last 50FPS to get to 12FPE. I am using stock hammer and spring, TP is .137. What would be the best way to get another 50FPS? Thanks, Don

[BigTinBoat]

My 1720T field target pistol is shooting 730FPS with 8.4 JSBs. I have a JDS regulated 13CI tank so air is not an issue but I can't seem to get the last 50FPS to get to 12FPE. I am using stock hammer and spring, TP is .137. What would be the best way to get another 50FPS? Thanks, Don

TP is .137? that seem a bit on the larger size. Mine is .109, I have a heavier spring and I'm getting almost 16fpe.

[doninva]

What spring are you using?

[FuzzyGrub]

Don,

My guess is that it is your reg set-point or plenum size that is holding it back.  or other mods (valve) are needed to get to that power at your current set-point.

Like Rob, I am running 10.3g JSB at 800fps with a 1720T, with a 0.110" TP, BSB o-ring buffer, and slightly heavier spring: http://www.mcmaster.com/#9434k65/=11e3h5s

I get about 23 shots from 3k to 2K. 

[BigTinBoat]

What spring are you using?

I too am using the 1.5" x .30 x.042.

I didn't notice the "regulated" part in your post. Like John mentioned it's the reg pressure. Not sure what you have it set at, but it's gonna have to be around 2K I'm sure to get what we are getting unregulated. I stop shooting when mine gets down to 2K.

[nervoustrigger]

I agree with Fuzzy and Rob, take a look at the regulator pressure.  The stock valve, hammer, and spring will easily make over 12fpe in unregulated form.  With the transfer port that large and a generous plenum (since bottled and not an in-tube reg), my guess is you can hit 12fpe with 8gr pellets with as little as 1500psi.