Well my Disco Carbine is now a completed project. It was a long time coming as the LW barrel took forever to come and now to the details of the little beauty.
It started off as a factory Disco and from there the following have been done:
Everything was designed for it to be a .25 caliber Disco
Added a BNM Weaver style Multi breech with shroud
Cut 3 from the air tube
Installed a 16 LW choked barrel
Custom valve and transfer port
Hammer (striker) was modified to incorporate a means to Adjust Stroke Length for more flexibility in tuning
Disco Double Tube
Gauge was relocated to the back end of the Double Tube and utilizes the same stock hole as the factory gauge used. This permitted a big increase in air flow through the valve, seeing there were no valve block restrictions. It also added an extra 1 ½ to the normal Double Tube
Modified to be able to us higher fill pressures (do not try this with your Disco as it could be a safety issue)
Brass ends to both air tubes
Brass barrel band
Added a custom brass Power Adjuster
Custom brass trigger
Modified QB78 Target Stock
Three screw trigger mod with hardened pins and lubed
Depinger in the factory tube to reduce ping

All the machining and custom parts where done by Lloyd of Airgun Lab and he worked his magic to get me the FPE I was looking for and with a great number of shots. Without his help this would never have turned out so nice. THANKS LLOYD! I was hoping for a minimum of 8 shots and kept my fingers crossed that I would get 12 - 16 and as it turned out I'm getting 24 but I have much more tuning to do. Pretty difficult to tune when no one has the Kodiak or Barracuda 31.2 grain pellets in stock, PA just got the Kodiaks in and I ordered 8 tins, still have 8 tins of Barracudas on order since April 30th. When you look at the shot strings you will need to remember that this is a .25 caliber 16 barrel Disco Carbine. I was told by a good number of AG PCP enthusiasts when I started that with a 16 barrel and being a .25 caliber it was going to be very difficult to accomplish.




Now for the shot strings:
1st string is for the one 3 shortened factory barrel: Fill pressure 2400 PSI Ending Pressure 900 PSI DO NOT USE MY STARTING PRESSURE IN YOUR DISCO AS IT IS ONLY BUILT TO HAVE A MAX OF 2000 PSI. MINE HAS BEEN MODIFIED TO ACCEPT HIGHER PRESSURES

794.81 - 856.32 - 817.51
805.22 - 855.11 - 798.32
820.56 - 854.14 - 775.41
830.87 - 847.14 - 741.86
849.29 - 836.73 - 701.81

Now for the 1st string with the Double Tube:
Fill pressure 2400 PSI Ending pressure 1100 PSI DO NOT USE MY STARTING PRESSURE IN YOUR DISCO AS IT IS ONLY BUILT TO HAVE A MAX OF 2000 PSI. MINE HAS BEEN MODIFIED TO ACCEPT HIGHER PRESSURES

798.00 - 858.81 - 836.21
814.54 - 860.82 - 823.58
825.37 - 855.17 - 817.29
828.42 - 860.40 - 806.13
830.41 - 861.68 - 792.41
844.02 - 851.98 - 778.10
848.87 - 848.57 - 760.88
856.08 - 840.15 - 743.27

2nd String with Double Tube
Fill pressure 2450 PSI Ending pressure 1100 PSI DO NOT USE MY STARTING PRESSURE IN YOUR DISCO AS IT IS ONLY BUILT TO HAVE A MAX OF 2000 PSI. MINE HAS BEEN MODIFIED TO ACCEPT HIGHER PRESSURES

795.22 - 836.15 - 839.69
811.21 - 849.05 - 831.44
811.97 - 852.46 - 825.71
826.27 - 860.64 - 815.04
829.44 - 858.26 - 802.87
832.01 - 856.98 - 790.81
842.78 - 853.6 - 778.05
846.67 - 847.56 - 758.64

So as you can see the Double Tube mad a big difference in the shot string and power that this little Carbine has. I have more testing to be done when my pellet supply arrives!! If you have been thinking about adding a Double Tube Kit to your Disco just imagine what it would do to your Disco if I gained the extra shots and power with my 16 Carbine.

Norm

it's that well done.

Very nicely done Norm. A few questions if you don't mind.

Did you modify the QB stock yourself? I didn't recognize it at first. How much work was involved in reworking it to fit the Disco? It looks great on your Disco!

Can you provide any details about the valve modifications?

I'm really impressed!

Thanks for sharing,

Dan

''If everything seems under control, you're not going fast enough!'' Mario Andretti

Hi Dan
The QB78 Target Stock was not too bad to modify for the Disco. The hardest part was patching the stock where the original stock bolt was as it partially in the same area as the Disco's gauge hole was going to go. So when I cut the area out of the butt section to make it very much different from most stock I was able to use that piece of wood to cut a plug to fill the original bolt hole. Other than that it was just a matter of opening up the action area to 5/8" so the Disco action could slide in. Everything was pretty much straight forward.
The valve was a complete new valve that is very different. The gauge was removed from the factory tube and installed in the new Double Tube. This was done to add a little extra length to the Double Tube and remove it from behind the valve removing the air restriction is causes. Now the new valve was made longer to cover the gauge hole in the factory tube and seeing there was no gauge there that area was opened up as far as possible. This gave a much better flow of air which my Carbine was going to need. The front end of the valve was also modified to permit better air flow and the transfer sleeve and port was enlarged as much as possible. The new valve was drilled to accept a #10 bolt in place of the #8 and the bolts were rated at a much higher strength. This permitted a much higher fill pressure, 2600 PSI is not an issue and I could go to 2800 PSI without any problem. The hammer was modified in a couple ways that also helped. One being a stroke adjustment rod was added so now the Carbine not only has a power adjuster but a stroke adjuster. We were going to add a needle valve in the valve discharge but decided not to as I knew I wanted as much air as I could get. I did have one string that was in the mid 60 FPE but I did not get as many shots as I wanted so I tuned things down for now. I will be going back and try to tune it to get 16 shots with an average of the mid 60's FPE. Will need t play with springs and stoke adjustment to manage that. I'm using 31.02 Barracudas & Kodiaks and I am down to about 50 pellets and everyone is out of stock on them. PA just got the Kodiaks in and I have a 1000 coming in so I will be able to tune my Little Carbine to where I want it and then start to see how it groups. This being out of stock on .25 caliber pellets did create a small problem with getting things done.
I wanted something different that no one would have and I think I got it!

BTW My Carbine would never have had the power and shot count if it was not for the Disco Double Tube
Checkout my website discosrus.net

Norm

I forgot about DiscosRus. I had checked them out a few weeks ago. I've got a Disco that I plan to do some modding on. I haven't had time to even think about what I want to do yet.

Thanks for sharing the details with me. Good luck on getting it tuned to your liking.



Dan

''If everything seems under control, you're not going fast enough!'' Mario Andretti