HW90 Beeman RX2 Theoben gas ram DIY pump how to

[marx68us]

One of the reasons I bought the HW90 was that I found that you can change the ram pressure. Basically variable power.
You need a few things. You can buy the whole kit ready from best fittings in the UK for 85EU plus shipping and taxes. This is the slim jim pump. There's no pressure gauge though. Why I don't know.

If you want to build your own kit the first thing you need is the theoben gas ram adapter from Best Fittings or Rapid Air Weapons.
The threads on the adapter are 1/8" BSP (british standard pipe). Our goal is to get to a schrader valve.
1. Theoben adapter $30
2. Viair 90001 1/8" Female BSP - 1/4" Male NPT Adaptor  $6 - Amazon
3. BrassCraft 1/4 FIP x 1/8 FIP reducer 119-42xP Lowes $4
4. Pro plumber air valve 1/8 Lowes part 77200 $3.50
5. RockShox High-Pressure Shock Pump 600psi with gauge $43 Amazon
6. Some pipe thread tape or sealant
$86.50 total
Now you can tune your RX2 and or rebuild it. Of course this adds value to your air rifle since you could sell the kit with it.
Plus you get a bike pump for other things. The gauge reads in PSI and BAR so you know how much to pump it.

[Txfish219]

Thank you for the concise list of necessary items!
Anything else to share on thus - anyone?

[straightshooter]

Great info! Thanks for taking the time to share. Would be handy as a sticky.

[marx68us]

I'm glad I made this setup. It does work. Make sure to use plumbers tape on the joints. I started hearing something crunchy. I wasn't sure what it was then the auto safety stopped working. At first I had no idea. But I noticed after cocking that the cocking lever was lose at the barrel pin. I had already worn it out after my 1000 shots since buying it. I made a pin for it but the lever is also worn a little. The original pin was half way cut through!  I found a hardened steel die that had the same 5mm diameter and cut it to length to use it for a while. I plan on finding a bronze bushing or maybe even a bearing to place into the cocking lever so this never happens again. Considering the force that joint takes, it should have been made better.

I was going to tear it all down, but thought I'd wait for a new seal to come in along with the factory pin. Before the partial tear down I did de-pressure the chamber. The pump did fill it back up no problem. I stopped at 22 bar just to see how it cocks. I think that dropped it to 30-35lbs. Too easy. Still shot 21gn at 640fps. But I'm having inconsistent results. Hence the need for a complete rebuild. I guess I don't need a new spring huh?

[Yogi]

Is that the one that has a max bar of 150 and a recommended pressure around 130-135?  How are the piston different?
Thanks,

-Y

[Sfttailrdr46]

The Max recommended fill pressure for the gas spring on the RX2 is 24 Bar and slightly lower ~22 Bar seems to give the best results so 24 bar = 348 PSI & 22 Bar = 319 PSI

[marx68us]

HW90 is rated for 26 BAR. It's stamped on the chamber. I pumped it to 25 BAR to see if it still worked good. Yep. Smoother than when I got it.  I'm stoked knowing that I can tune it down to whatever I want. After my repair it's really shooting great. My first impressions were that I shouldn't have bought it. Screws coming lose, trigger all over the place, hard to cock, inaccurate and hard to hold. Yeah, sounds like I'm reviewing a china made gun. These need work also. Loctite & Lube!

[RICKR71]

Thanks for taking time to post your DIY. Im not sure i understand the list though. The goal is to go from 1/8 BSP 'Male' to shrader i understand, but why is the next item (2) a female 1/8 BSP to male 1/4 NPT? I ask because the end of the RAW or Best Fittings looks male and larger, and if you know; what is that thread on it?
thanks again, and if you have pictures all the better!

rapidairweapons.com/xcart/product.php?productid=17629&cat=255&page=2

[marx68us]

1/8" BSP technically measures 9.6mm Don't ask me why it's called 1/8", IDK. It measures closer to 3/8".


I can't post pics, just add the "https:"
//picasaweb.google.com/lh/photo/YBUdYGVHZHULg6F7tRa90NMTjNZETYmyPJy0liipFm0?feat=directlink

This shows the assembled adapter. There is a zip tie around it since I leave it in my case.
Updated Link.

Thanks for taking time to post your DIY. Im not sure i understand the list though. The goal is to go from 1/8 BSP 'Male' to shrader i understand, but why is the next item (2) a female 1/8 BSP to male 1/4 NPT? I ask because the end of the RAW or Best Fittings looks male and larger, and if you know; what is that thread on it?
thanks again, and if you have pictures all the better!

rapidairweapons.com/xcart/product.php?productid=17629&cat=255&page=2

[Yogi]

Sorry, I can not get the link!

-Y

[Sfttailrdr46]

  When I got my almost new RX2 the piston pressure was still at the factory setting . The original owner sold it because it was harsh shooting and I made him an offer that was irresistible. His RX2 + a few $$ for a very nice almost new Beech stock .25 caliber Air Arms S510 . Long story short I dropped the pressure in the Piston slightly and have the RX2 shooting @ 910 FPS and ~20 FPE sweet rifle that will remain as my favorite magnum break barrel . With the laminated stock and deep bluing on the barrel she is a beautiful and accurate .20 tack driver 

[Dmorcos]

I am considering the WH90, but also want to be able to tune it (pressure wise) if I get one.

Is there a kit or a package that can be purchased vs. having to purchase all the separate components and building one?

thanks

[marx68us]

Best Fittings in the UK sells a slim jim pump. But there's no pressure gauge. When the RX2's came out Beeman did sell a pump kit, but then decided to drop that since people were over pressurizing it.
But really it's not a big deal to make this kit. I've listed all the parts. Just screw them together with plumber's tape and you are ready.

https://picasaweb.google.com/lh/photo/YBUdYGVHZHULg6F7tRa90NMTjNZETYmyPJy0liipFm0?feat=directlink

[straightshooter]

HW90 is rated for 26 BAR. It's stamped on the chamber. I pumped it to 25 BAR to see if it still worked good. Yep. Smoother than when I got it.  I'm stoked knowing that I can tune it down to whatever I want. After my repair it's really shooting great. My first impressions were that I shouldn't have bought it. Screws coming lose, trigger all over the place, hard to cock, inaccurate and hard to hold. Yeah, sounds like I'm reviewing a china made gun. These need work also. Loctite & Lube!

Howdy, I do not own this AG, but interested in it.

I am a little confused, according to best fittings UK, (and if I am comprehending correctly), I am led to believe that once you release the factory pressure you can not return to the factory pressure without using factory components?

"The pump is not designed to take a 12ft/lbs rifle to, for example,
18ft/lbs or more. This high power is only achieved by factory
components"

http://www.bestfittings.co.uk/pdf/Theoben%20&%20HW90%20Gas%20Ram%20Pump%20Instructions%20NEW.pdf

E

[Sfttailrdr46]

HW90 is rated for 26 BAR. It's stamped on the chamber. I pumped it to 25 BAR to see if it still worked good. Yep. Smoother than when I got it.  I'm stoked knowing that I can tune it down to whatever I want. After my repair it's really shooting great. My first impressions were that I shouldn't have bought it. Screws coming lose, trigger all over the place, hard to cock, inaccurate and hard to hold. Yeah, sounds like I'm reviewing a china made gun. These need work also. Loctite & Lube!

Howdy, I do not own this AG, but interested in it.

I am a little confused, according to best fittings UK, (and if I am comprehending correctly), I am led to believe that once you release the factory pressure you can not return to the factory pressure without using factory components?

"The pump is not designed to take a 12ft/lbs rifle to, for example,
18ft/lbs or more. This high power is only achieved by factory
components"

http://www.bestfittings.co.uk/pdf/Theoben%20&%20HW90%20Gas%20Ram%20Pump%20Instructions%20NEW.pdf

E

If you have the fill adapter and a HP hand pump you can raise and lower the pressure as desired. Just make small changes in pressure and monitor the results with a chrony

[straightshooter]

Yep understood. Rephrasing question:

Can the factory pressure setting be filled up with the use of a hand pump (like described in this post) or is this not possible with the hand pump and only doable with factory components as the link suggests?

Thanks

E 

[Yogi]

Yep understood. Rephrasing question:

Can the factory pressure setting be filled up with the use of a hand pump (like described in this post) or is this not possible with the hand pump and only doable with factory components as the link suggests?

Thanks

E

Why don't you contact Theoben USA to find out.  They are the experts...
-Y

[straightshooter]

Yep understood. Rephrasing question:

Can the factory pressure setting be filled up with the use of a hand pump (like described in this post) or is this not possible with the hand pump and only doable with factory components as the link suggests?

Thanks

E

Why don't you contact Theoben USA to find out.  They are the experts...
-Y

Since they no longer produce a pump, I doubt they would offer much help? My question pertains to the home built pumps like described in this thread. I thought perhaps someone may have tried?

E

[Txfish219]

Do you need to remove the stock to add air?

[Txfish219]

Do you need to remove the stock to add air?