.25 Disco fever.... add another project to the pile

[lloyd-ss]

Some of you guys do such beautiful work...... beautiful fits and finishes and design.... lots of patience and craftsmanship.
My stuff..... well, it is usually very functional.  Let's leave it at that.  Works like gang busters (or breaks), and looks good at 10 feet... no close-ups, please.  Time to move on to the next project... somebody else finish up the details. 
I'm glad we all make such a nice mix of styles on this gate.  Everybody seems pretty comfortable with there skill level and everyone is very supportive and helpful, and that is very, very, cool.  Thank you, everyone! 

So a short while ago I traded David some odds and ends for a used Disco stock because I wanted to keep my original intact for special reasons, but I wanted do some mods.

Here are some first pics.  .437 O.D. x 30" long .25 cal barrel (barrel liner from Mike Sayers).  Not sure how long the barrel will be in the end.  An additional airtank of 4130 steel 1" O.D. x .063 wall x 19.75 long.  Should give about 180 more cc's after deducting for threaded end plugs.  (standard disco is about 135 cc's or so)  I will connect the 2 tubes in the area of the gauge port.  I might move the fill nipple to the lower tube and add a new triple barrel band, and LDC.  Time will tell.  I've modded the internals of the Disco to get 49fpe in .22 cal.  rsterne has gone a little higher, so I guess i have to, too, sigh.    Gotta stay on your toes around here!! 
That big power was sucking the air up so this extra tube will more than double the tank volume.
I'll keep it coming, no promises on when, though.  Lots of little parts and pieces to make.

Happy Labor Day everyone,
Lloyd

P.S. I haven't looked around, but someone might have already done this. 

[gene_sc]

WOW!!!! Great idea Lloyd. On the same lines as the Careers air tube setup. More air to push them big chunks of lead out the barrel. Now we need to fix you up wiff real nice stock fer her... Never seen a mod like this one before Lloyd.

I love your comfort zone Lloyd. Wish I had that talent. More pics to come I hope. Keep us appraised buddy.

[pindog2000]

Lloyd I must say your a man of many talents.

[bradyman1]

Definately a project to keep an eye on. Great idea. Those discos seem to be a very popular building platform. Looks great so far. Good luck!

[lloyd-ss]

WOW!!!! Great idea Lloyd. On the same lines as the Careers air tube setup. More air to push them big chunks of lead out the barrel. Now we need to fix you up wiff real nice stock fer her... Never seen a mod like this one before Lloyd.

I love your comfort zone Lloyd. Wish I had that talent. More pics to come I hope. Keep us appraised buddy.

Gene, I added the emphasis on your words in the quote.  Actually in my opening sentence, your Beji Disco project was one of the nice ones I was thinking about. 
Lloyd

[dk1677]

Great project Lloyd!

[Rescue35]

i have to, too, sigh.   
Happy Labor Day everyone,
Lloyd

Ha, you said to-to...

Looks great LLoyd! I'll definatly keep an eye on your progress.

[rsterne]

Great idea and will make a handy hunter for sure.... MuzzleMack was working on a dual tube Disco setup but I don't know if he ever finished and tested it.... it was just a "personal project" gun.... I believe he was going to build it as a .25 also....

There are pretty limited choices in .25 cal ammunition for medium to higher powered PCPs.... ranging in weights from the 25.3 gr. JSB Kings to the 43.2 gr. EunJin Pointeds.... Virtually everyone seems to have settled on the JSBs at between 950-1000 fps as the best long range pellet, although some barrels seem to work well with the .25 cal Predators and the 31 gr. Baracuda/Kodiaks.... Lots of guys use the EunJins for shorter distances, but they don't seem to have the accuracy/trajectory for the long ranges.... I know there are custom bulllets available that are heavier, they just aren't common....

The point of that last paragraph was to suggest that you aim for about 50-60 FPE for your project.... I got 58 FPE with my .25 cal Disco, but only about 8-9 shots.... so I detuned it to 45 FPE (11 shots).... With you having more than double the air, you should be able to hit the mid 50s and still have reasonable efficiency and shot count....

Have you thought of the possibility of a regulator between the two tubes?.... run the lower tube at 3000 psi and the upper at a regulated 2000?.... 

Bob

[1377x]

now thats a great idea!

[lloyd-ss]

Great idea and will make a handy hunter for sure.... MuzzleMack was working on a dual tube Disco setup but I don't know if he ever finished and tested it.... it was just a "personal project" gun.... I believe he was going to build it as a .25 also....

There are pretty limited choices in .25 cal ammunition for medium to higher powered PCPs.... ranging in weights from the 25.3 gr. JSB Kings to the 43.2 gr. EunJin Pointeds.... Virtually everyone seems to have settled on the JSBs at between 950-1000 fps as the best long range pellet, although some barrels seem to work well with the .25 cal Predators and the 31 gr. Baracuda/Kodiaks.... Lots of guys use the EunJins for shorter distances, but they don't seem to have the accuracy/trajectory for the long ranges.... I know there are custom bulllets available that are heavier, they just aren't common....

The point of that last paragraph was to suggest that you aim for about 50-60 FPE for your project.... I got 58 FPE with my .25 cal Disco, but only about 8-9 shots.... so I detuned it to 45 FPE (11 shots).... With you having more than double the air, you should be able to hit the mid 50s and still have reasonable efficiency and shot count....

Have you thought of the possibility of a regulator between the two tubes?.... run the lower tube at 3000 psi and the upper at a regulated 2000?.... 

Bob

Right now I have more questions than answers: barrel length, valve flow capacity, pellet vs bullet, valve chamber vol control vs regulator.  I think I will just play and see what falls into place.  The pellet and vel info is helpful.  If I stick with the long barrel, the 31 gn barracudas might work out.  Pellet vs bullet is a serious consideration at so many different levels, but I will at least have to try some bullets to see what they do.  That really changes the nature of the Disco, though, probably in a direction that I do not care to go.  I would like to avoid a regulator if I can and think I will try partitioning off the valve chamber first to see how that will affect velocity consistency and efficiency.  For me, I think this disco will be a learning tool. 
With the spring compression limited to about .500" and the actual hammer stroke being only about .660, I wonder how limiting that is for the total power of the set-up?  Where is the true bottle neck?  What about the little transfer port between the tank and barrel?  Has anybody altered that, for better or worse?  Do the tall breech blocks use the same dia port?? Many folks are using those.  A delicate balance there.  All that said, backing down from that max always yields such an improvement in shot count.
Thanks for the input.  I am looking forward to this. 
Lloyd

[dkwflight]

Hi LLoyd

Looking good so far.

Let us know how the mod performs.

[airpuffhunter]

go for it lloyd a .25 on a disco is a good idea even if it gets only 9 shots

[rsterne]

The transfer port on my .25 cal Disco is the same size as I use on a .22 cal.... 0.166" ID.... With a bottom fed barrel about teh biggest you can go is 3/4 of the bore or the pellet has trouble loading past it.... That would be 3/16" on a quarter bore.... That's what my Hayabusa uses, and yes the transfer port is taller because of the repeater breech....

Bob

[Toolmaker]

Wow, great idea! This will be interesting for sure.

[MustangMike]

Book marked and eagerly awaiting updates

[lloyd-ss]

Well, she's up and running!
I finished it up very late last night.  Filled it with my shop compressor... no leaks.  Filled it to 1000 psi... leaked at the gauge (o-ring fitting), tightened it up and the leak stopped.   Filled it to 2200 psi and went to bed.  This AM, still at 2200 psi.  I have to tell you, that is very unusual for me, LOL.   



The air transfer from tank to tank happens in the gauge fitting area. I had opened up the old gauge fitting (the one that fits in the tube with 2 o-rings) to get free flow from the front of the tank and 50fpe in the .22 version.  With the new adapter I made, I bored it out most of the way, but just left a small hole to the front of the tank to start with it slightly choked down  on power.  Still, I just took one shot at 2200 psi with a .25 Barracuda (30.1 gn) and got 787 fps = 41.4 fpe.  I think that's a good starting point. 

I'll shot a string with this fill and then take it apart to get some detail pics.  The new tank more than doubles the HPA volume, so I think I'll have to go for more power to make it seriously worthwhile.  This could be a nice hunting set up, or worthy of a .25cal Marauder 8 shot clip.  Even with the long barrel, hearing protection or a shroud are in order.  So far, so good!

Lloyd

[rsterne]

Good first trial.... I'm watching over your shoulder.... 

Bob

[Rescue35]

Sweet!

[lloyd-ss]

Well, I think I got lucky on this one.  There is a leak around the transfer port because I can feel a little puff of air every time the gun is fired.
I managed to shoot a 46 shot string with the .25 cal Disco with 310 cc of reservoir and 30" barrel.
30.1 Barracudas, 46 shots, starting at 2200 psi and shooting down to 1040 psi.
Average FPS = 768, Std Dev 15 FPS,   Average FPE = 38.4 Std Dev 1.5 FPE.
The string is a little ragged because of the air leak, but overall, I am very happy with how flat the string is for a first pass, IMHO.  I think fixing the air leak will smooth out the line.
Lloyd

[rsterne]

Very nice, Lloyd.... Interesting the first couple of shots were a slightly higher velocity than usual.... otherwise a nice flat shot string.... What was the velocity range, about 8%?.... Excellent efficiency as well, 39.4 x 46 = 1812 FPE from 310/16.4=18.9 CI with an 80 Bar drop = 1512 CI for 1812/1512 = 1.20 FPE/CI....

What does the gun weigh?....

Bob