Benjamin Marauder Pistol Huma Regulator install issues

[jumsted]

Working on installing a Huma regulator for dad in his p-rod. It’s not going smoothly.

Dad wants the reg installed without the pressure gauge. No matter what I try, the plenum doesn’t want to seal without the pressure gauge assembly installed. Another post on this forum suggested pressurizing the gun and dry firing 20x in order to get the seals set. Tried that several times. reversed the plenum. No luck. Still more than a little air escaping the hole for the gauge.

Instructions say a spacer may or may not be present behind the pressure gauge. I don’t see it there. If the red metal inside the tube is a spacer, it’s not coming out. The surface on which the plenum o-ring should seal looks scratchy and uneven, so not surprised it’s leaking.

installing the reg and plenum with the pressure gauge in place, with front o-ring removed, works. Only get a few shots before cylinder pressure drops below reg pressure, so it’s hard to tune.
dad wants more than 700fps, which sounds reasonable enough. Increased reg pressure from about 130 to about 140 bar. Started with minimal hammer spring tension and worked up. Still get no more than 620fps even with hammer spring turned all the way up, at which point things go wonky. Also tried increasing hammer throw distance which didn’t do much of anything.

If anyone can suggest how to get the reg installed without the pressure gauge, that would be amazing. Can work on tuning from there. I know it’s a matter of getting everything balanced and working together. Left a voicemail with AOA, who might not be available until monday.

 

[Pale_Rider]

You don’t need the pressure gauge adapter anymore. Just install the reg and plenum.

 

[3Crows]

If you use plenum 1258 with the regulator and with no gage block then the O-ring in the bag 1258 (upper left) goes in the aft end of 1258 and seals directly to the forward end of the exhaust valve.



Your dad may want 700 fps but I am thinking your dad is not going to get 700 fps without doing some porting of the barrel and the transfer port or replace the transfer port with a larger ID plastic tubing, still porting the barrel.

What velocity did the pistol shoot at prior to the regulator when it was charged with only 130 to 140 bar? That will be your velocity or very close to what it will be with the reg installed and set to 130 to 140 bar, less actually due to the now smaller plenum now charged to 130 to 140 bar instead of the entire reservoir volume at higher pressures. The only way to increase the velocity will be to port the barrel and a larger ID TP.

 

[Motorhead]

That done ... less hammer weight or a lot softer hammer spring. Bstally o-ring mod might even help as lower operating pressure with any thing close to OEM hammer strike energy will way over dwell valve !!

* yes for a face o-ring seal to work, sealing surface Must be Even, flat and Smooth.

 

[jumsted]

If you use plenum 1258 with the regulator and with no gage block then the O-ring in the bag 1258 (upper left) goes in the aft end of 1258 and seals directly to the forward end of the exhaust valve.



Your dad may want 700 fps but I am thinking your dad is not going to get 700 fps without doing some porting of the barrel and the transfer port or replace the transfer port with a larger ID plastic tubing, still porting the barrel.

What velocity did the pistol shoot at prior to the regulator when it was charged with only 130 to 140 bar? That will be your velocity or very close to what it will be with the reg installed and set to 130 to 140 bar, less actually due to the now smaller plenum now charged to 130 to 140 bar instead of the entire reservoir volume at higher pressures. The only way to increase the velocity will be to port the barrel and a larger ID TP.

Thanks. This is what I have, so o ring inside both ends of the plenum which seems to seal against the air gauge housing ok, but not against the valve housing when gauge is removed. Was getting 630 fps before the regulator and am back close to that, 622fps.

 

[3Crows]

What does the face of the exhaust valve look like? Is it rough or damaged then it will not seal? You will then need to remove the exhaust valve and inspect the face, polish out evenly any damage if possible and maintain squareness of the abutting surfaces.

The velocity sounds about right to me for the small plenum and regulator set pressure. To get the velocity up you will need to address the valve outlet port, transfer port inside diameter, barrel port inside diameter or a larger plenum volume at expense of reservoir HP capacity.

 

[jumsted]

That done ... less hammer weight or a lot softer hammer spring. Bstally o-ring mod might even help as lower operating pressure with any thing close to OEM hammer strike energy will way over dwell valve !!

* yes for a face o-ring seal to work, sealing surface Must be Even, flat and Smooth.

Thanks! Wonder if it’s worth removing the valve housing and trying to polish the face.

 

[3Crows]

Thanks! Wonder if it’s worth removing the valve housing and trying to polish the face.

Yes, that is what I am saying to do. Remove the exhaust valve and inspect that sealing face and if rough, scratched, or damaged, if possible polish it.

 

[weevil]

Thanks! Wonder if it’s worth removing the valve housing and trying to polish the face.

Yes, smooth the face and while you have the valve out, drill the valve exhaust to .140. Then order a .140 transfer port from hill airgun. You can drill the stock port out if you’re handy. As pointed out by Motörhead, with a reg, the stock hammer is much more than needed. Hill also sells a lightweight hammer which works well with a regged setup preventing hammer bounce. Otherwise, expect to use very light spring tension with the stock hammer. Anyway, you will absolutely need to increase porting to get the power you desire.

.140 should get you around 24 18-19fpe shots with ~125 bar reg.

 

[Dr. Kralenstein]

If you're dad is just wanting power, then why go regulated? Could just port and turn up the hammer spring. It'll do over 20 fpe for 2 mags easy.

The regulator takes up a decent amount of reservoir space on these guns. Adds headaches as well... which you've found out.

 

[jumsted]

If you're dad is just wanting power, then why go regulated? Could just port and turn up the hammer spring. It'll do over 20 fpe for 2 mags easy.

The regulator takes up a decent amount of reservoir space on these guns. Adds headaches as well... which you've found out.

I tried to talk him out of it. Shot fine unregulated. He wanted a fun project, only at 88 he doesnt have the vision, strength or fine motor control to do the work, so I’m stuck with this steaming mess. Increasing the power was an idea he had after the reg was installed.

Removing the valve, polishing the face and opening the port is more work than I want to do. Even with the schematic, I’m unclear on how to remove the valve assembly. Looks like the whole gun would need to be disassembled.

I turned the reg down to 125, set hammer spring tension and throw to their minimums, increasing both slowly, just looking for consistency, which I haven’t yet found. Only get 10 shots before it falls off the reg. Without the reg it gets about 24 shots, which is fine.

Looks like I’ll remove the reg and try to get things back to where they started.

 

[waltermitty]

I seriously considered the regulator mod but after reading what one needs to do to retrofit the unit I opted to enjoy the pistol in stock form. I didn't feel the tradeoffs were worth it for me as a beginner PCPer

 

[Pale_Rider]

Do you still have the pressure gauge block (adapter) inside the air tube with the plenum and regulator? If so, that would explain why your shot count is so low.

 

[redsqnm]

If you use plenum 1258 with the regulator and with no gage block then the O-ring in the bag 1258 (upper left) goes in the aft end of 1258 and seals directly to the forward end of the exhaust valve.



Your dad may want 700 fps but I am thinking your dad is not going to get 700 fps without doing some porting of the barrel and the transfer port or replace the transfer port with a larger ID plastic tubing, still porting the barrel.

What velocity did the pistol shoot at prior to the regulator when it was charged with only 130 to 140 bar? That will be your velocity or very close to what it will be with the reg installed and set to 130 to 140 bar, less actually due to the now smaller plenum now charged to 130 to 140 bar instead of the entire reservoir volume at higher pressures. The only way to increase the velocity will be to port the barrel and a larger ID TP.

Where can I get a side lever breech like you have in this pic ?

 

[Dr. Kralenstein]

Where can I get a side lever breech like you have in this pic ?

Here is an option off of ebay. I bought a 30 cal setup for the crosman 2240 platform from him. Took about 3 weeks to get here, and George has great communication.

SL Match Grade Breech, Benjamin Marauder Gen2, Gen1 Cal .177, .22, .25*, .30* | eBay

Side Lever Match Grade Breech for Benjamin Marauder for both Gen1 and Gen2 Mrods Cal. 177. 22. 25 . 30 . Highest quality Match Grade Side Lever Breech for Benjamin Marauder for both Gen1 and Gen2 Mrods.

www.ebay.com

 

[3Crows]

Side levers are great, I have a couple of the JSAR and the one from eBay (Georgia). Either requires a number of modifications to install and $$. Do yourself a favor and just get this from AGR instead:

Marauder Thumb Rest - Airgun Revisions

Add a bit of comfort when cycling your charging handle with this AR exclusive Thumb Rest. Just screw into back of air tube. Rest your thumb on it while grabbing charging handle and squeeze your hand. Aids in smoother cocking as well bringing your index finger lower on bolt handle…

www.airgunrevisions.com

Instead of having to pull the bolt back, just place the thumb on the rest and the index finger or fingers on the bolt in close to the bore axis as possible and squeeze the hand like squeezing a rubber ball. Cocking is super easy. Yeah, side levers are nice, the one from Georgia still needs the thumb rest whereas the one from JSAR with a much larger lever does not.

All of the above applicable to the rifle, not sure what works with the pistol.

 

[3Crows]

The Marauder in any iteration is about as easy to disassemble/assemble as it gets in the air gun world. To remove the valve the rifle/pistol needs to be disassembled. Then a piece of PVC pipe or a wooden dowel can be used to push the valve out the front (not the rear). Good opportunity to deburr some areas and replace all of the seals (either from a hardware store or eBay or call Crosman with the part numbers written down and quantity).

 

[jumsted]

Do you still have the pressure gauge block (adapter) inside the air tube with the plenum and regulator? If so, that would explain why your shot count is so low.

Yes, I know. Thanks.

 

[jumsted]

The Marauder in any iteration is about as easy to disassemble/assemble as it gets in the air gun world. To remove the valve the rifle/pistol needs to be disassembled. Then a piece of PVC pipe or a wooden dowel can be used to push the valve out the front (not the rear). Good opportunity to deburr some areas and replace all of the seals (either from a hardware store or eBay or call Crosman with the part numbers written down and quantity).

Good point. Thanks. It doesn’t look difficult.

However, given my luck, it wouldn’t go well. Dad’s RAW micro and Air Venturi compressor both had problems recently. I spent days trying to fix both and ended up sending both in for service. It was fun and I learned a lot, but…

 

[Frank in Fairfield]

I was going the regulator route.
Bought one.
Didn’t use it.
Sold it and all of my PCP gear: three rifles, one pistol, compressor, two tanks, parts, three scopes, etc….
I was forced back into the PCP game last year.
Now just the PRod, Tank, compressor.
15fpe at just shy of 700fps with a couple of adjustments.