Author Topic: 200FPE Disco Build .357 (Read 5169 times))

rsterne · « **Reply #20 on:** October 27, 2016, 12:48:08 AM »

A Disco valve that I modded myself.... It has a 0.266" throat with a PEEK poppet and the stem is 1/8".... The exhaust port is 0.219" on a 20 deg. angle, and the transfer and barrel ports are also 7/32".... The valve was optimized for a .25 cal bullet shooter or a .30 cal pellet shooter, so is a bit undersized for a .357, even with pellets.... However, trying to get much more power from a Disco than what I did (my gun peaked at 192 FPE at 3000 psi) will leave you with just one shot per fill from the single 135 cc tube, without a drop in velocity.... I plan to install a Cothran Powerhouse Valve in my Disco Double as soon as I can get some shop time.... It is, in fact, my first winter project.... I am hoping for two shots of equal velocity as close to 200 FPE as I can get (with a 127 gr. bullet).... but I hate making predictions, there are just too many variables....

Bob

TroyHammer · « **Reply #21 on:** October 27, 2016, 01:44:13 AM »

The goal was to get a 5 shot string averaging 100fpe so you are giving me hope. I'm going to redo the transfer port and add a heavier spring tomorrow. We'll see what happens. A tip on the cothran valve. Use a front screw breech. The valve body has enough meat to drill and tap for a 6-32 bolt. I bought 5 of them at the depot for only .98¢ In stainless. I shortened one. Turned the head down on the lathe so it is the same dia. as the stock breech screw and you can attach the breech directly to the valve. Just drill the threads out of the tube. Very secure with the amount of air it pushes. It stripped the threads and blew the breech off during the first test. Wasn't using any barrel bands.

rsterne · « **Reply #22 on:** October 27, 2016, 01:53:23 AM »

My breech on the Disco Double currently uses a 4-40 SHCS tapped into the tube in between the front and back stock holes, but the breech has a breech band that holds down the front, so strength is not an issue....

Bob

TroyHammer · « **Reply #23 on:** October 28, 2016, 01:01:00 AM »

Got 3 shots today at 108fpe avg. Installed a heavier spring and a new brass transfer port. The rubber one I was using collapses in on its self when the breech was tightened and limited air flow. Getting a little blow by but once the new breech is made I should be able to fix that. Going to have a 150cc tube made for the gun and should get 5 shots over 100fpe. May look in to a longer barrel as an option. I just want to be able to offer the Airgun world over 100fpe Bigbore entry level gun @ $400 add your own trigger/stock. That's the reason I am going with the discovery/22xx trigger pattern. People can use the trigger group and stock off a 2260/ disco/ maximus/ 2289 that they already own or I can add a trigger group and stock and sell the full rifle. Accuracy tests begin tomorrow. Hopefully all goes as planned.

oldpro · « **Reply #24 on:** October 28, 2016, 01:13:40 AM »

Quote from: TroyHammer on October 28, 2016, 01:01:00 AM

Got 3 shots today at 108fpe avg. Installed a heavier spring and a new brass transfer port. The rubber one I was using collapses in on its self when the breech was tightened and limited air flow. Getting a little blow by but once the new breech is made I should be able to fix that. Going to have a 150cc tube made for the gun and should get 5 shots over 100fpe. May look in to a longer barrel as an option. I just want to be able to offer the Airgun world over 100fpe Bigbore entry level gun @ $400 add your own trigger/stock. That's the reason I am going with the discovery/22xx trigger pattern. People can use the trigger group and stock off a 2260/ disco/ maximus/ 2289 that they already own or I can add a trigger group and stock and sell the full rifle. Accuracy tests begin tomorrow. Hopefully all goes as planned.

Troy I can't tell you how bad and idea this is for you. The liability alone is enough to kill this idea but you will find like many before you that it costs far more than you think it will and profit margins will be very small. I'd suggest to you to make your own gun and share your results and have fun with it.JMHO

TroyHammer · « **Reply #25 on:** October 30, 2016, 08:27:50 PM »

I finally got to do some testing. 3300psi fill 5 shots starting at 823-730fps 108fpe avg ending at 1800 psi. Tube does still have a gauge block so that is taking up some room. Re-crowned the barrel and getting 5 shots a 50 yards less than 1-1/2" with the first 4 shots less than 3/4" at 50 yards. Using a Maximus stock and trigger. A better trigger will really help out as well.

TroyHammer · « **Reply #26 on:** October 30, 2016, 08:32:37 PM »

rsterne · « **Reply #27 on:** October 30, 2016, 08:52:35 PM »

Sound like you can back down the hammer strike a bit and even out the shot string.... lose a bit on the first shot but use less air and end up with a narrower ES.... 11% is a bit of a spread, IMO....

Bob

TroyHammer · « **Reply #28 on:** October 30, 2016, 09:12:25 PM »

Rsterne I agree. It still needs some final tuning but darn happy with the grouping. Now to get started on the new breech.

TroyHammer · « **Reply #29 on:** October 31, 2016, 01:16:34 AM »

Rsterne I was able to acquire 24" barrels from the same maker. With new tubes made out of stainless 3500psi rated with out the gauge block and keeping .25" transfer port I believe 150+ fpe with pellets over 5 shots will be obtainable. Does that seem like asking too much?

rsterne · « **Reply #30 on:** October 31, 2016, 01:35:48 AM »

Just make sure that EVERY part of the gun is safe for 3500 psi.... Valve screws are an obvious one, but it's easy to forget things like the bolt handle shearing off when you fire the gun.... There is 350 lbs. of force on that ever time you pull the trigger, so at the ASME's 3.5:1 safety margin it needs to be good for 1225 lbs. without shearing off.... That's just an example of something you may not think of that could bite you....

5 shots at 150 FPE with pellets?.... You are still only dealing with 9 CI of volume without the gauge block.... However, if the stars align for you, you never know unless you try it.... I got 9 shots averaging 130 FPE with 77.5 gr. pellets with my Disco Double, starting from 3000 psi.... It had a 28" barrel and 0.220" ports, but it had over 15 CI of air in the reservoir....

Bob

TroyHammer · « **Reply #31 on:** October 31, 2016, 10:47:26 AM »

125fpe with pellets was what I meant and hoping 150fpe with some slugs. With the new longer barrels I may try to add an inch or two to the tube as well.

Thanks
Troy

TroyHammer · « **Reply #32 on:** November 17, 2016, 10:12:25 PM »

Annihilator .357 update:

Replaced the 21" .357 barrel, which was getting 108fpe, with a 28" barrel. Should put this rifle just beyond 135fpe. Chrony tests in the morning. Still have to fit the barrel band.

Monkeydad1969 · « **Reply #33 on:** November 18, 2016, 12:07:58 AM »

Very nice, Troy.

Joe

TroyHammer · « **Reply #34 on:** November 18, 2016, 12:56:21 AM »

Quote from: Monkeydad1969 on November 18, 2016, 12:07:58 AM

Very nice, Troy.

Joe

Thank you Joe. Still have to blue the barrel and dye the barrel band but it should look pretty good when I'm done.

Monkeydad1969 · « **Reply #35 on:** November 18, 2016, 01:04:17 AM »

Need to put my .357 barrel to use.

Joe

TroyHammer · « **Reply #36 on:** November 20, 2016, 03:56:36 PM »

Annihilator .357 update

New 28" barrel. 1st shot 889.5 fps and 142fpe 3000 psi. Drops to 125fpe over 3 shots. Testing has shown this valve to work best on a regulator. Looks like a bottle fed baby to be born soon.

oneshot61 · « **Reply #37 on:** November 20, 2016, 04:02:11 PM »

Very cool!! Nice looking gun, your ready to hunt!!

Monkeydad1969 · « **Reply #38 on:** November 20, 2016, 04:40:42 PM »

I really want to see it as a bottle fed beast and the numbers you get then. What regulator are you using?

Joe

TroyHammer · « **Reply #39 on:** November 20, 2016, 07:32:53 PM »

I really like the Robert Lane regulator. Will probably regulate the tube to 2000psi and run a 3000 psi tank.

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200FPE Disco Build .357

Author Topic: 200FPE Disco Build .357 (Read 5169 times))