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

[lloyd-ss]

I know what you mean RE the O-ring cutting.... I HATE that big hole for the gauge.... I'm making an extended valve front end to replace the gauge block tomorrow that moves the O-rings ahead of the gauge hole....

Bob

Bob, Excellent idea on that new extended front end and eliminating that o-ring cheese grater!
Lloyd

[rsterne]

I couldn't find any tapered springs anywhere, so I did a mod on the stock valve spring today.... I tapered it!!!

I slid/screwed a 17/64 drill inside about 3/4 of the way and tapped it with a hammer on an anvil until I could pull it straight out.... then I repeated with a 9/32" drill in about half way and then a 19/64" drill in about 2 coils.... I finished with a 5/16" drill in about 1.5 coils and ended up with a spring that is stock on one end (to fit the valve head) and it's 19/64" ID and 3/8" OD on the other end.... That will allow me to drill the new valve front out to 19/64 (0.297") instead of 1/4".... increasing the area of the inlet side of the valve by 41% over stock.... In addition, it will sit in a 3/8" drilled seat in the front end....

It is currently sitting in a 500*F oven for 1/2 hour to re-temper it and stress-relieve it after the pounding I gave it.... Hopefully that will allow it to live.... I'll post a photo of my valve front end in my 9mm/.308 Disco thread in the Big Bore Gate when finished....

Bob

[airpuffhunter]

Hi Bob
wouldn't it be better to do a little longer valve body and then do the holes in the out side of the valve body like you did in the Tf 78 project

[rsterne]

The Disco valve seals to the tube at the front, not near the poppet where the valve comes apart like the QB78.... In addition, in a Disco tube, there is a 1/2" hole for the gauge about 3/4" ahead of the front of the valve.... that means that the air reservoir has to be sealed bridging that area as well.... That's where my extended valve front end will seal.... An additional problem is the hole for the front trigger mount, so even if you were using a 22XX or custom tube the seal would have to be ahead of that anyway (ie where the Disco valve seals)....

The way my QB valve is cut away will only work if that portion of the valve is ahead of the point where the valve seals the air reservoir....

Bob

[gene_sc]

Great idea about fixing the issue with o'ring getting pinched in that big hole... I hated that also. Love Lloyds term "Cheese Grader".. That is a perfect description....
 
I wanted to mention something. To adress the issue with the front breech mount hole in tube. To me that is the perfect place to put the breech hold down screw but gets in the way of multishop designs. I also thought of another ideas for my next Disco breech. The hole in top of breech that hold the barrel down. Drill through base of breech block. Of course the hole would be smaller than the actual hole at top for set screw that holds barrel in place. Locate, drill and tap into the valve body. Using a bottom tap. Or just drilling and tapping hole in tube. The o'ring on valve would be forward of the hole. At this location there should be plenty of meat to tap the valve body without going through. That would solve my issue with the front hole in tube for mounting the breech. Maurader's use two hold down screws that go through tube and into valve body.
 
Gene

[rsterne]

If I understand you correctly, you are talking about bolting the breech down directly above the front trigger screw?.... If  you use a single bolt that would be under the barrel.... Since you have to slide the barrel into the breech before the breech is bolted down (so that the assembly can drop over the trasfer port).... then you have no way to access the head of the screw because the barrel is in the way.... or am I misunderstanding you?.... Two screws like the way the MRod is done would work, providing the breech is wide enough so the screws can miss the barrel....

Bob

[gene_sc]

You would tighten the front breech screw to tube down before inserting the barrel and locking it down. Front breech hold down screw would be under barrel.
 
The hole would be in front of the port.

[rsterne]

I understood correctly, then.... so you must not have the transfer port coming up to the barrel or you wouldn't be able to slide the barrel in once the port is in place as normally the transfer port projects into a recess on the barrel.... I guess the port seals to the breech only?.... Do you use O-rings to seal to the barrel like a QB?.... or not bother?....

Bob

[gene_sc]

Maybe this chicken scratch drawing would help understand what I am saying...
 
Gene

[rsterne]

I got it, Gene.... but I don't think you understand my concern.... With the front breech bolt UNDER the barrel you have to install the breech first, tighten the screws, THEN slide the barrel into place from the front....

HOWEVER, the transfer port and O-ring have to be installed into the breech AFTER the barrel is in place in the breech.... It looks to me like the top of the transfer port projects above the bottom of the breech and into the barrel.... or at least the O-ring presses against the barrel.... If you install the transfer port in the breech, and install the breech, the transfer port (or at least the O-ring on it) will prevent you from sliding the barrel into place....

How do you do both?....

Bob

[gene_sc]

OK Bob, now I see what you mean.. Pretty thick head here. Guess I can scratch that idea unless I can find a majician in the house...
 
Gene

[rsterne]

Sorry....

Bob

[gene_sc]

No problem Bob... I am here to learn. Thanks for you help.. Always welcome.
 
Gene

[lloyd-ss]

I've been pondering this. Gene, I agree that the current disco breech attachment system leaves some improvement opportunities.  The M-rod and P-rod more or less fixed that with the 4 outboard screws.
Bob, you mentioned that the QB uses o-ring to seal the barrel.  Do they use two internal o-ring grooves, one on either side of the xfer port,  that the barrel slips thru and thus stops leakage during firing. It certainly would be nice to be able to secure the breech first, and then slip in the barrel.
Lloyd

[Rocko]

Thats exactly what I did !  I made a multi breach for my Disco. & drilled & taped 8-32 threads directly across from the stock screw.  I cut 0-ring groves on each side of the t.p. in the barrel just the same as the QB-78 set up.  Used a 5/16 x 3/8 long set screw directly above to secure barrel & give access to mounting screw below.  Gives a much more solid mounting & you can remove barrel without removing breach.  At the time I was thinking of being able to do a quick caliber change.  Used a simple 0-ring to seal breach to valve t.p.  Shoots great & no leaks.

[gene_sc]

Looks like  you guys have solved the problem... Thanks a bunch.. still learning....
 
Gene

[lloyd-ss]

Learning is what its all about...... and having fun.
Rocko thanks for the info. What kind of I.D. grooving tool did you use?
Thanks,
Lloyd

[Rocko]

I.D. grooving tool for what ?  I cut o-ring grooves on the barrel with a parting tool in my lathe. Not sure what you are referring to.  Thanks

[lloyd-ss]

Rocko,
I thought you cut the grooves inside the breech where the barrel slides in, not on the O.D. of the barrel.
Lloyd

[Rocko]

No problem LLoyd,

I guess my original discription my not have been very clear.  The only I.D. o-ring groove I cut was inside the breach end of the barrel to seal the bolt probe.  I ground it from a standard 1/4" lathe tool.  It was a tight fit in a .22 barrel but worked out OK.  Don't know if I can do it with a .177 barrel or not.  Will find out one of these days.