Help with Theoben mk1

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AirSupply

AirSupply

Member
Jan 12, 2017
1,419
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Victoria, Australia
I know there are some very knowledgeable Theoben forum members and I’d like some advice on how to get more power from this gun. This gun was given to a mate along with a Fabre tank. Couldn’t believe his luck! I like the gun a lot. It’s well made and seems very accurate with the Jsb Kings (It’s .25cal). It’s shooting them under 800fps at the moment. Accurate but I’m sure it could be just as accurate and up the fps considerably. I’d really like to be able to shoot slugs from it. It will shoot slugs very accurately at short ranges. (50m) The barrel seems to have virtually no choke. I really feel it a very good barrel

I’m pretty sure this is how this gun would have come straight from Theoben and it is in great condition. So far all I’ve done is purchased the picatinny rail after clamping the dovetail rings to what I thought was a dovetail tail.....I’m learning. 
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These are the things I’d like advise on

1. The trigger is ...... shocking what can be done?

2. I’d like to regulate the gun and add a quick fill rather than take the bottle off. Could I use the huma if I make up and adapter?

1578977322_6392102275e1d482ae52323.17410070_583089A1-7254-4944-9FE1-6E2F7DDDA97D.png


Or is there a better option?

3. If I have a bottle regulator will I need plenum space between it and the gun? 

4. If I have the quick fill can I just remove this piece from the gun? Is it only there to open the valve on the bottle?
1578977682_8179685895e1d4992efa369.25052197_C7F8E148-9B64-486D-BD81-DC5EB6A6259B.jpeg


Im enjoying learning more about these guns and can see why they have such a strong following. Look forward to your advise and AGN wisdom. 
Michael
 
The THEOBEN receivers just like RAW "Non X" versions have limited plenum volume & struggle in .22 and IMO simply can't make big power as a .25 regulated gun.

If running UN-Regulated then it just comes down to the valve breathing well enough, transfer path including barrel port large enough. 4.5 - 5mm is pretty ideal.

Fast flow bottle connection needs larger ports too so the shot can actually use bottle volume for the shot & not just the plenum space within the mono block.

Hammer weight and spring driving it more in play ... Tho still by design they were never designed for big power.



While there are ways too and some may have monster power theobens ..... not common and a whole lot of work & non OEM spec parts and pieces likely required.



JMO tho ... having never worked on just one ... LOL


 
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There are plenty of options, to get the most power it’s best to go with a free flow from the bottle to block, that way the entire volume of the buddy bottle becomes the plenum. The down side is poor shot count due to the useful power curve that is inevitable in an unreggulated gun, The power curve can be flattened out by balancing the valve and hammer spying but it is time consuming.

The transfer port in the block are small so restrict air flow, this was done to help flatten out the curve but it drastically reduces the ability to produce power. You can open the top port to a maximum of 6mm. You will need to tap out the top of the transfer port to exempt a bigger barrel location grubscrew.

To open out the bottom prechamber to valve camber transfer port is a little more tricky and requires very carefully measuring and drilling. Pm me for details, or you can drill and tap trough the bottom of the block, fit a q/f and use that to drill a second prechamber to valve chamber port.



To gain the most power, the hammer pip should be 6mm, remove the inertia wieght, make a heavy brass spring guide that extends into the space left by the inertia weight.

Unregulated, free flow, 21” barrel, sending.25kings supersonic is not a problem, with a reg 950fps is about the most you will get but that requires a different setup

Let us know what you are thinking.

Bb




 
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The THEOBEN receivers just like RAW "Non X" versions have limited plenum volume & struggle in .22 and IMO simply can't make big power as a .25 regulated gun.







Click to expand...

65fpe from a .25 regged rapid or a RAW1000 is not difficult but does require a few upgrades,. The maximum power j have ever achieved from an unregged rapid was 135fpe from a .30 cal.. 

Personally, I would choose one of my rapids to build a 100fpe gun than my impact.



Bb
 
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