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Air Gun Home Forum Index » Rifles » Disco Tops 52 FPE Goto page 1, 2  Next    View previous topic :: View next topic  Disco Tops 52 FPE   Posted: Sat Nov 28, 2009 5:55 pm rsterne Moderator Joined: 15 Jan 2008 Posts: 2998 Location: Coalmont, BC I tore my Discovery apart again over the last couple of days and did everything I could think of to maximize the valve volume and ease the flow both into and out of the valve.... I shortened the threads in the valve to 0.3" and bored the inside to 0.60" ID.... The volume is now over 3 cc, 50% more than stock.... I drilled the inside of the exhaust seat to 0.228" (#1 drill) and slimmed the valve stem to 0.115".... The exhaust port is drilled to 0.161" (#20) and angled 20 degrees and streamlined.... The transfer port is 0.166" (#19) and the barrel port 0.169" (#18 ).... The front of the valve is tapered and countersunk as large as possible while maintaining sufficient wall thickness.... The gauge port was countersunk from both ends and then the through hole milled out (off center to miss the gauge seat) to 5/16" ID and streamlined.... I used my 1.75" x 0.040" wire hammer spring, cranked to within 1/4 turn of coil bind.... and pumped the gun to 2500 psi.... Here are the results, in all cases only those shots over 96% of the maximum velocity reached with each pellet are shown: Hobbies are now supersonic, and the first 4 shots with 14.3 gr. JSB Express were also.... The highest power achieved was with 28.7 gr. EunJin Domes which peaked at 909 fps which is 52.7 FPE, with the peak occurring at 2000 psi.... They also recorded the best shot string, and the greatest efficiency of all the tests done at maximum power.... Here are the details: Pellet; Avg. Velocity, Avg. Energy, # Shots to 96% RWS Hobby 11.9 gr.; 1205 fps, 38.4 FPE, 5 shots JSB Express 14.3 gr.; 1146 fps, 41.7 FPE, 6 shots JSB Exact 15.9 gr.; 1114 fps, 43.8 FPE, 6 shots JSB Exact Heavy 18.0 gr.; 1066 fps, 45.5 FPE, 7 shots Beeman Kodiak 21.0 gr.; 1019 fps, 48.4 FPE, 7 shots H&N Rabbit Mag. 24.8 gr.; 948 fps, 49.4 FPE, 8 shots EunJin Domes 28.7 gr.; 900 fps, 51.6 FPE, 10 shots EunJin Pointed 32.4 gr.; 843 fps, 51.1 FPE, 10 shots I then tested the JSB Heavy 18.0 gr. pellets, which I know are very accurate in this gun, at two and fours turns out on the velocity adjuster.... The results are also shown on the graph above.... In summary: Hammer Spring Setting; Avg. Velocity, Avg. Energy, # shots and pressure range used, (JSB Heavy 18 gr.) Maximum; 1066 fps, 45.5 FPE, 7 shots from 2500 psi to 1800 psi 2 Turns Out; 1000 fps, 40.0 FPE, 14 shots from 2400 psi to 1500 psi 4 Turns Out; 913 fps, 33.3 FPE, 14 shots from 1900 psi to 1100 psi Considering these results, I don't think there is much point in trying a 2-piece valve (like the one I made for Kinetic_Genius) in a Discovery.... The air reservoir is simply too small to supply a valve larger than this one.... At maximum power levels, even with heavy pellets, the shot string is down to just 10 shots.... What I do plan on trying is converting this gun to .25 cal.... I have a 24" Lothar/Walther .25 cal. top end kit coming from Mountain Air.... it's "in the mail".... Bob Last edited by rsterne on Sat Nov 28, 2009 9:18 pm; edited 1 time in total _________________ Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! Airsonal: Too many to count!   Posted: Sat Nov 28, 2009 6:29 pm sniper Silver Status Member Joined: 28 Nov 2008 Posts: 3752 Location: Star, Idaho that is absolutely amazing and impressive bob!!!!! _________________ I believe in gun control, If there's a gun around I want to be controlling it.......   Posted: Sun Nov 29, 2009 3:59 am AirGunEric Site Admin Joined: 20 Jan 2007 Posts: 6929 Location: "Out There" Give Bob a drill and look what happens! _________________ ` I'd say "I care." But I'd be lying. Canadian Airgun Supplier: http://www.scopesandammo.com/storefront   Posted: Sun Nov 29, 2009 7:54 am fritz Silver Status Member Joined: 25 Nov 2008 Posts: 2442 Location: New Jersey- outside of Philadelphia So when are you going to start selling these monsters, or offering a tuning service? _________________ "I never set out to be wierd, it was always everyone else who called me it" -Frank Zappa Speed is impressive, accuracy is deadly. It's not that I'm not a people person, it's just that I'm not a stupid people person.   Posted: Sun Nov 29, 2009 12:49 pm sniper Silver Status Member Joined: 28 Nov 2008 Posts: 3752 Location: Star, Idaho bob's next post will be titled.... .22disco vs. .22 LR. _________________ I believe in gun control, If there's a gun around I want to be controlling it.......   Posted: Sun Nov 29, 2009 3:11 pm Midichlorian Veteran Member Joined: 25 May 2009 Posts: 333 Location: Middle of the Desert fritz wrote: So when are you going to start selling these monsters, or offering a tuning service? Yeah im interesting in tuning service if you can work your magic with a marauder too. Im sure you get even more impressive numbers out a Marauder. let me know if you ever offer this service. Put me first on the list _________________ .22 Benjamin Marauder Join http://airgunspace.ning.com It`s Like Myspace for air gunners!   Posted: Sun Nov 29, 2009 4:02 pm sniper Silver Status Member Joined: 28 Nov 2008 Posts: 3752 Location: Star, Idaho sorry mid. marauders are illegal in canada. _________________ I believe in gun control, If there's a gun around I want to be controlling it.......   Posted: Sun Nov 29, 2009 6:16 pm fritz Silver Status Member Joined: 25 Nov 2008 Posts: 2442 Location: New Jersey- outside of Philadelphia Shh... the Mounties will never know. Hell, the gun doesn't even make any noise! _________________ "I never set out to be wierd, it was always everyone else who called me it" -Frank Zappa Speed is impressive, accuracy is deadly. It's not that I'm not a people person, it's just that I'm not a stupid people person.   Posted: Sun Nov 29, 2009 6:22 pm rsterne Moderator Joined: 15 Jan 2008 Posts: 2998 Location: Coalmont, BC Quote: Shh... the Mounties will never know. Hell, the gun doesn't even make any noise! Yeah, but unfortunately even getting one into Canada isn't going to happen.... Has anyone pulled a valve out of a Marauder yet?.... What does it look like?.... Bob _________________ Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! Airsonal: Too many to count!   Posted: Sun Nov 29, 2009 6:32 pm fritz Silver Status Member Joined: 25 Nov 2008 Posts: 2442 Location: New Jersey- outside of Philadelphia I'm sure there would be a loophole of some kind. Not to say that I would do such things as exploit said theoretical loophole(s)... Crosman likely has a diagram on their website. _________________ "I never set out to be wierd, it was always everyone else who called me it" -Frank Zappa Speed is impressive, accuracy is deadly. It's not that I'm not a people person, it's just that I'm not a stupid people person.   Posted: Sun Nov 29, 2009 7:16 pm sniper Silver Status Member Joined: 28 Nov 2008 Posts: 3752 Location: Star, Idaho Has anyone pulled a valve out of a Marauder yet?.... What does it look like?.... Bob[/quote] not me. i'm not mechanically inclined. i'm leaving that up to joe. if he'd every get back online that is. _________________ I believe in gun control, If there's a gun around I want to be controlling it.......   Posted: Sun Nov 29, 2009 7:24 pm Jaxom Senior Member Joined: 06 Aug 2008 Posts: 927 Where's the pictures!!!??? Some of use would like to learn how to do this type of work. Having pictures would be handy for reference sake. RE Maurader diagram. Crosman HAD that posted, I noticed reciently when I went back to grab a diagram of the my discovery, they no longer have it posted. I'll see if I can lay my hands on it and have my buddy scan it for me. Then I'll post it some it up on the forum. _________________ .22 2300kt Crosman Custom   Posted: Mon Nov 30, 2009 8:21 pm Midichlorian Veteran Member Joined: 25 May 2009 Posts: 333 Location: Middle of the Desert sniper wrote: sorry mid. marauders are illegal in canada. *wipes tear* _________________ .22 Benjamin Marauder Join http://airgunspace.ning.com It`s Like Myspace for air gunners!   Posted: Mon Nov 30, 2009 8:40 pm fritz Silver Status Member Joined: 25 Nov 2008 Posts: 2442 Location: New Jersey- outside of Philadelphia Midichlorian I am yourdaddy! _________________ "I never set out to be wierd, it was always everyone else who called me it" -Frank Zappa Speed is impressive, accuracy is deadly. It's not that I'm not a people person, it's just that I'm not a stupid people person.   Posted: Mon Nov 30, 2009 10:47 pm Midichlorian Veteran Member Joined: 25 May 2009 Posts: 333 Location: Middle of the Desert fritz wrote: Midichlorian I am yourdaddy! I searched my feelings and know it to be true. So what are you getting me for Christmas Dad. _________________ .22 Benjamin Marauder Join http://airgunspace.ning.com It`s Like Myspace for air gunners! 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