Benjamin Marauder questions 12-20 fpe

[Shears]

New to PCPs and working on my first gun, a .177 Marauder I want to be able to tune from 11-20 ft lbs energy for FT Competition.  I'm installing HuMa regulator.  My questions are:
1. I don't understand why there's a throttling screw near the transfer port.  Why would you ever want that anything other than wide open, especially if running a regulator?
1.5 Should I modify the transfer port for larger ID?

2. Why is the reservoir tube free-floated in the stock?  Is that for thermal management of some sort?

3. Why is the barrel shroud free-floated?  Then to make matters worse, they almost free-floated the barrel until they put that tip on itthat the baffle spring pushes on.  This all seems backwards.  The shroud should have set screws on the front support so they can be used to center the shroud on the barrel center, and the barrel inside should be free floated with the baffles only touching the shroud.

4. What is conventional wisdom on the hammer setup?  Longer stroke lighter spring, or shorter stroke heavier spring (or preload)?

It's hard to type this on iPhone!  😂  Hopefully that made sense.

[Tims229]

I'm sure some of the good tuners will answer your questions. Some info will help them answer. What caliber is your marauder? That will help them steer you in the right direction better. If trying to keep fpe low I would not open the transfer port, generally that's for more power.

[Jr_Explorer]

I assume you have a .177 caliber M-Rod.  I have a .177 regulated M-Rod.  No transfer port change.  Throttling screw wide open.  I was shooting for 19.75 fpe with this set-up got FT as well.  I like it a lot.

[c_m_shooter]

If you are going for 12 ft lb, you need to adjust the transfer port down to bring the power down and get a good power curve before installing the regulator.  The regulator should be set to a pressure that is near the downside of the power curve to avoid a big spike in power coming off the regulator.  You will not be able to switch back and forth from 12 to 20 ft lbs easily.  If you reduce power with the hammer spring leaving the transfer port wide open you will not get as consistant velocity.

[Buldawg76]

New to PCPs and working on my first gun, a .177 Marauder I want to be able to tune from 11-20 ft lbs energy for FT Competition.  I'm installing HuMa regulator.  My questions are:
1. I don't understand why there's a throttling screw near the transfer port.  Why would you ever want that anything other than wide open, especially if running a regulator?
1.5 Should I modify the transfer port for larger ID?

2. Why is the reservoir tube free-floated in the stock?  Is that for thermal management of some sort?

3. Why is the barrel shroud free-floated?  Then to make matters worse, they almost free-floated the barrel until they put that tip on itthat the baffle spring pushes on.  This all seems backwards.  The shroud should have set screws on the front support so they can be used to center the shroud on the barrel center, and the barrel inside should be free floated with the baffles only touching the shroud.

4. What is conventional wisdom on the hammer setup?  Longer stroke lighter spring, or shorter stroke heavier spring (or preload)?

It's hard to type this on iPhone!  😂  Hopefully that made sense.

Billy
I will answer your question as best I can since I have a unregulated 177 Mrod I use for FT as well.

1. The air screw is there to help fine tune the velocity for your particular application. It controls the air flow to either allow for full power tune ( wide open at 5 1/2 turns out from fully bottomed in valve throat, just bottom lightly ) or turned in to as little as 1 turn out for a low power tune to give high shot counts. Mine is at 2 turns out and is shooting JSB 10.34s at 900 fps.
1.5. if you want to keep as high as shoot count as possible I would not increase the TR port at all. it is plenty big enough to provide the flow to tune for FT whether shooting in the open class ( 12fpe ) or the hunter class ( 20fpe ). if you open it up you will lose the ability to tune down as easy for a low power tune. Mine is still stock.
2. The reservoir is free floated in the stock to allow for the expansion and contraction of the tube when under pressure and different temperatures that affect the tube pressure. The tube also has harmonics that occur when shot that could affect accuracy if it was in contact with the stock ( the ping noise you hear when firing ).
3. The barrel is free floated inside the shroud since the baffles do not apply enough pressure on the barrel to create any issues. The O ring at the front of the barrel on the diffuser keeps the barrel centered in the shroud and serves to help direct the air blast rear ward inside the shroud for good sound absorption. The front barrel band is there more for protection against bumps to the barrel/shroud so it does not get bent excessively. The band should be adjusted so that it does not touch the shroud at all and so its centered around the shroud with a even clearance all the way around the shroud. It has a o ring inside the barrel aside of the band so it never should make hard contact with the shroud.
4. The hammer is there to be able to tune to your preference and the results of adjusting it is light spring/ short stroke tension equals low power/high shot count and high spring tension/long stroke equals high power/low shot counts. its another tuning aid that helps fine tune for your desired power level. Mine is at 5 turns in on hammer spring and 2 turns in on stroke adjuster.

Here is a tuning guide written by one of the top ranking FT shooter using the Mrod

https://docs.google.com/document/d/1WFDife1EqVkkDQPEwRZFU6Kawki2sCi0x5KdFarO86U/edit?hl=en_US&pli=1

Hope this helps.

Mike