Marauder with Huma Reg and Lightweight Hammer

Sounds like you have a bad o-ring(s) somewhere. Air shouldn't be venting out like that.

Did you open up the air passages? When I regged my MRod I opened all passages with a 5/32" bit. Set the reg at 120bar (iirc) and was getting over 20fpe.

I would actually suggest 120 to 125 Bars on your regulator. I think 110 bars of pressure is too low without additional work done on your Marauder.

Now if you want to port the barrel larger, Put in a larger transfer port, and add an upgraded valve, you might get away with 110 bars of pressure.

The side is vague. Do you mean the O-ring which seals the bolt?

The side is vague. Do you mean the O-ring which seals the bolt?

Click to expand...

No I mean on the side of the air tube through the velocity screw - right side of the gun. It is also venting from behind the hammer.

Click to expand...

There is no O-ring there. You should have a adjuster screw and a "locking" set screw.

Here's link to exploded parts. The valve is on page 4



https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=13&ved=2ahUKEwiKmaDBreHcAhULylMKHYrhDMAQFjAMegQIBxAC&url=https%3A%2F%2Fwww.crosman.com%2Fpdf%2Fmanuals%2F1763%2520%26%25202263%2520EVP%2520%26%2520PL.PDF&usg=AOvVaw0vyo7hk8tltFrXmCFJiX72

It almost sounds like the locking screw may have caused the adjusting screw to turn in farther then you wanted. I would remove them both and then put the adjusting screw back in with a little thread sealer (blue not red) then just snug the locking screw on top so that it doesn't change the adjustment. This could also explain your low velocity.

Happened to me too.

The locking set screw (gold color) is possibly missing. Keep in mind if you use the locking screw and you tighten it down, you will more than likely turn the velocity screw in, lowering the velocity of the pellet.

First, determine you velocity screw setting you need counting the exact amount of turns. 

remove.

wrap the velocity screw about half the length and twice around with Teflon tape being very careful not to allow any to get into the valve. 

Re-install.

Some may suggest thread lok or fingernail polish and those will possibly seal the leak. However, with Teflon tape any adjustments have a more positive feel and stays in place.

And BTW...that wisp of air you are feeling has little to no effect on velocity.

I tried all of what was suggested - primarily threadlocking the silver velocity screw. Both parts are present. I am not over tightening the set screw. I'm only screwing it in enough so that it is recessed into the gun.

Still getting a pretty significant shot of air through that screw.  I think it's the valve allen screw next to it. I think I'll change the o rings on the valve and see if that helps.

Anyone know what size o-ring the valve takes? If not I'll just order a resealing kit.

Click to expand...

If air is coming out of the valve retention screw hole only when you discharge the gun then there is NO o-ring on the gun you can change to make it stop.

He's right, NOT the valve oring , if the oring was bad it would leak all the air period.

You really need to ID the leak location. Soap & water or perhaps talk power depending on area. Put power right in that hole & see. 

John

Guys, just a FYI, when I was tuning my Marauder for 12 ft lbs., which is an 8.44 grain pellet @ 800 FPS. I installed a Hill high flow valve, that does not have a transfer port adjustment, and a 25 gram Hill hammer, which has no adjustment, the striker is flush with the hammer, all the way rearward. I had a lighter hammer spring in it, and adjusted it all the way out. I also have a Hill transfer bushing between the valve and the barrel. I turned the Lane regulator down to around 1000 PSI, down from the 1375 factory setting from Lane. The SLOWEST I was able to get that 8.44 grain pellet was 1150 FPS.

On your air blowby issue, you should not have ANY air puffing or bleeding out from anywhere. The several things to check would be, as mentioned, the transfer port screws and setscrew. All advice above is correct, by tightening the setscrew, to secure the transfer port screw, it has a habit of screwing in, reducing your velocity and power. One other thing to check.... the o rings around the transfer bushing between the valve and the barrel. If those orings are damaged just a little ( and it's really easy to do, they are a little tricky), that could easily lose a substantial amount air in the equation. These are special orings that are flat, not rounded. If you use regular orings instead of the proper ones, it could leak air. The first order of business, is to locate where the air is coming from. That's sometimes the hard part. Once that is done, we can diagnose a fix, most likely a simple one. Keep us posted.

Tom Holland