GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: tjcib on February 01, 2015, 06:18:09 PM
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Well, actually 34 shots. Two strings listed below. You can see the labels (JSB 18.13 vs. CPHP 14.3). ES<4% This basically puts the JSB at a 20 FPE setup, or 19 FPE for the CPHP (but dropping off rapidly at distance)
My question of, "with this velocity, can I still dispatch squirrels effectively" was also answered . I took an adolescent gray squirrel down with a JSB. Pellet did not pass all the way through, but it got the job done...
Shot # CPHP JSB 18
1 759 687
2 761 684
3 759 684
4 764 689
5 761 695
6 767 693
7 766 690
8 772 696
9 769 695
10 773 696
11 772 698
12 770 701
13 773 702
14 766 698
15 777 707
16 775 699
17 784 703
18 782 702
19 776 701
20 777 703
21 788 704
22 777 708
23 781 705
24 783 696
25 779 702
26 773 701
27 770 703
28 770 705
29 767 698
30 760 698
31 693
32 692
33 687
34 684
Average: 773.4 698.5
Min: 759 684
Max: 788 708
Spread %: 3.7% 3.4%
(https://lh4.googleusercontent.com/-IYCqS4rxDUI/VM6lFv4Ea5I/AAAAAAAAF0M/sYyNrsNOy3k/w605-h340-no/jsb%2Bvs%2Bcphp%2B2-1-15.png)
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Nice tune, that will take any squirrel out with no problem. I used to shoot my Disco set at about the same tune and took a few varmints with no problem.
Nice job
William
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Yeah, that's a good looking tune you have there! :D
As to the effectiveness on squirrel, for brain shots I would say that is about twice as much energy as you need at modest ranges (say, out to 35 yards). Or about right for vitals shots...I would expect a pass through and two holes is more effective than one for such shots.
Case in point, I built a regulated QB78 for a buddy a few weeks back that was set to shoot JSB 18.1gr at about 29fpe. A friend at work invited me over to thin out the squirrels in his back yard one Saturday. In this suburban setting, the longest shot would be about 30 - 35 yards so on the night before, I dialed back the rifle to 15fpe and re-zeroed. The following morning, dispatched 6 in a row:
http://www.gatewaytoairguns.org/GTA/index.php?topic=78577 (http://www.gatewaytoairguns.org/GTA/index.php?topic=78577)
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Yeah, that's a good looking tune you have there! :D
As to the effectiveness on squirrel, for brain shots I would say that is about twice as much energy as you need at modest ranges (say, out to 35 yards). Or about right for vitals shots...I would expect a pass through and two holes is more effective than one for such shots.
Case in point, I built a regulated QB78 for a buddy a few weeks back that was set to shoot JSB 18.1gr at about 29fpe. A friend at work invited me over to thin out the squirrels in his back yard one Saturday. In this suburban setting, the longest shot would be about 30 - 35 yards so on the night before, I dialed back the rifle to 15fpe and re-zeroed. The following morning, dispatched 6 in a row:
http://www.gatewaytoairguns.org/GTA/index.php?topic=78577 (http://www.gatewaytoairguns.org/GTA/index.php?topic=78577)
It was strange that I didn't get a pass through on the squirrel. Only thing I can think is that it got the shoulder on the way out, but I didn't have time to autopsy the little guy, and I wasn't eating him because he's been eating insulation in my attic.
My backyard range, including the yards of my neighbors who all gave me permission to thin squirrels, is about 55 yards. So this tune will have a little holdover to that far fence, but I'll figure it out.
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Hitting them right is the trick, your energy level will work just fine.
Mass produced PCP (Considering the WalMarts/etc. Crosman probably sell more Discos than any other PCP) isn't going to be finely tuned out-the-box. Looks like the current Crosman trend is to set them up to be faster/more powerful than the early versions at the expense of good shots per fill.
No fault there, getting "mo'power" is pretty much what most of the buyers in the first years were looking for.
Think you got it as good as you'd ever need a Disco to be.
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How did you tune your disco?
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thats awesome i get roughly 15 shots out of my disco.. maybe 20 but i dont have a chrony
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How did you tune your disco?
My tunings:
Three screw mod
Polished leade
Lapped barrel
Cut three full coils from stock hammer spring
Hammered the "nail" part out of a pop rivet and used the other part as the spring guide
A standard 1.5" 10-32 screw for power adjuster (will bling out later)
Oddly enough, I stumbled on this tune. With all the power adjuster parts above, I reassembled, turned the PA screw until the gun wouldn't cock, then backed it out to one half turn less than max...
Strangely, I thought that max point was "coil bind" on the spring. What was actually happening was the pop rivet was very long, and was keeping the hammer from fully cocking I intended for the coil being maxed as in what most people do, and thought that was happening until I shot over the chrony and only got 685 fps.
I knew something was wrong because a different spring guide with the same cut spring got me 780 fps with the same pellets. But the pop rivet was the exact length to restrict the hammer to this tune velocity.
Strange how sometimes the best discoveries (no pun) are accidents...
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^^
Nice. What's your address? I need you to tune my disco!
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Nice job. Good direction for a Discovery tune.
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How did you tune your disco?
My tunings:
Three screw mod
Polished leade
Lapped barrel
Cut three full coils from stock hammer spring
Hammered the "nail" part out of a pop rivet and used the other part as the spring guide
A standard 1.5" 10-32 screw for power adjuster (will bling out later)
Oddly enough, I stumbled on this tune. With all the power adjuster parts above, I reassembled, turned the PA screw until the gun wouldn't cock, then backed it out to one half turn less than max...
Strangely, I thought that max point was "coil bind" on the spring. What was actually happening was the pop rivet was very long, and was keeping the hammer from fully cocking I intended for the coil being maxed as in what most people do, and thought that was happening until I shot over the chrony and only got 685 fps.
I knew something was wrong because a different spring guide with the same cut spring got me 780 fps with the same pellets. But the pop river was the exact length to restrict the hammer to this tune velocity.
Strange how sometimes the best discoveries (no pun) are accidents...
Post is getting old but.... what's the length of your spring guide (rivet)?
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How did you tune your disco?
My tunings:
Three screw mod
Polished leade
Lapped barrel
Cut three full coils from stock hammer spring
Hammered the "nail" part out of a pop rivet and used the other part as the spring guide
A standard 1.5" 10-32 screw for power adjuster (will bling out later)
Oddly enough, I stumbled on this tune. With all the power adjuster parts above, I reassembled, turned the PA screw until the gun wouldn't cock, then backed it out to one half turn less than max...
Strangely, I thought that max point was "coil bind" on the spring. What was actually happening was the pop rivet was very long, and was keeping the hammer from fully cocking I intended for the coil being maxed as in what most people do, and thought that was happening until I shot over the chrony and only got 685 fps.
I knew something was wrong because a different spring guide with the same cut spring got me 780 fps with the same pellets. But the pop river was the exact length to restrict the hammer to this tune velocity.
Strange how sometimes the best discoveries (no pun) are accidents...
Post is getting old but.... what's the length of your spring guide (rivet)?
Yep, can't wait to see what the rivet length is also.
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Here are two pictures of the rivet. You can see it is about 3/8" long and the head diameter is 1/4"
You can also see the the tension placed on the rivet (which is made from a little softer metal) is actually damaging the rivet and deforming it a little bit. I did use that same rivet in the heavier hammer spring and cranked it to coil bind...but I imagine the cut stock spring for this tune would have caused some deformation as well.
(https://lh5.googleusercontent.com/-VlmgDnl9LpM/VOv-ZuSSHfI/AAAAAAAAF14/7b8i19e0108/w333-h591-no/15%2B-%2B1) (https://lh4.googleusercontent.com/-yaYS4DXs8l8/VOv-Zo4xpII/AAAAAAAAF2A/kVyHFjvaOGQ/w333-h591-no/15%2B-%2B2)
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Nice. What's your address? I need you to tune my disco!
Other than the cost of the JB Bore Paste, my tune cost me less than $5...
Can't say I lapped it all that well, or smoothed the leade out like the pros would, but at least I can say I did it, and it shoots .35" groups at 30 yards, so I'm happy. Hopefully my experience can get you close to what you're looking for.
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Thanks for the info Trevor.
FedEx should be arriving at my door today. Purchased from a fellow GTA member. Can't wait to see where she shoots as it's an older Disco (2010, as far as I can figure). I might order a new spring and try your mod. Your getting exactly what I am after.
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I just used a bolt that wouldn't quite fit inside spring with threads, chucked it in my drill press and filed off threads. Then flipped around and held by the filed off part and reduced head of bolt and rounded with file so it went inside endcap. I also drilled out Philips head slightly so my knurled thumbscrew (PA) from Macmaster-Carr seated right inside it. I too left it too long originally and had cut it down to just under half inch. I have also just drilled out endcap and tapped to fit a 5/8 bolt that I had drilled on thru center on a lathe and then I tapped for the 10-32 thumbscrew. Now I can remove bolt and change springs without disassembling gun.
(http://i1305.photobucket.com/albums/s560/mooseslayerjc/IMG_20150222_172510_zps74718fae.jpg?1424786901828&1424786902542)
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I, too, have a PA on the way that can change springs without disassembling. Much more convenient.
I thought about doing your exact method with a socket head screw as the spring guide, too, until I stumbled on a box of rivets at home and figured they would do until I figured out what I want exactly.
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I am going to cut down my hammer spring on my Disco as well, as it stands Im only getting 12-14 shots from 2000psi down to 1000psi. Any suggestions on how many coils to cut off? I was thinking of starting with 1.5 coils and see if I can get a decent tune with the 10-32 screw PA. If I can get anywhere close to this with mine I'll be a happy camper, the more useable shots the better ;D
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OK,
Here is how I did my Spring guide using a power adjuster I got from Norm at Discos R US. I did have to do a little modding on the adjuster screw so the guide pin I made would go all the way thru the adjuster bolt, you can make the spring guide as long as you want, you can even make it long enough so when it is cocked it sticks out the back and you can see if it is cocked or not. Just drill the hole all the way through the adjuster screw a little bigger. You will have to grind and cut some but not much and when you get it done it adds a little weight to the hammer, it also helps keeps the spring nice and straight with no binding.
Just look at the pics below, if you want one you will figure it out. I can adjust my Disco from 500 FPS all the way to 900+ FPS.
William
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I am going to cut down my hammer spring on my Disco as well, as it stands Im only getting 12-14 shots from 2000psi down to 1000psi. Any suggestions on how many coils to cut off? I was thinking of starting with 1.5 coils and see if I can get a decent tune with the 10-32 screw PA. If I can get anywhere close to this with mine I'll be a happy camper, the more useable shots the better ;D
I cut two off of mine. I was getting about the same as you stock. After I cut off the two coils and installed a power adjuster I got the following string using JSB 18.1 I shot it down to 800 PSI. The adjuster was .33 out from bind.
SHOT FPS FPE
1 653.6 17.2
2 654.5 17.2
3 660.1 17.5
4 659.1 17.5
5 661.4 17.6
6 660.8 17.6
7 668.3 18.0
8 666.1 17.9
9 666.9 17.9
10 669.5 18.0
11 669.2 18.0
12 671.8 18.2
13 674.2 18.3
14 673.4 18.3
15 678 18.5
16 679.8 18.6
17 673.9 18.3
18 679.2 18.6
19 677.5 18.5
20 675.4 18.4
21 673.9 18.3
22 674.9 18.3
23 675.6 18.4
24 676.5 18.4
25 670.8 18.1
26 666.8 17.9
27 665.5 17.8
28 663 17.7
29 657.4 17.4
30 649.7 17.0
31 647.8 16.9
32 639 16.4
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Those are some really nice strings on those Disco's. Perfect for lots of shots for targeting or small game at moderate ranges. Just think those are from a 2000 PSI fill and still getting good FPS for plenty of enjoyment, that tank of air will last a long time or just plain easier to pump it up if using a hand pump!
I do know if I turn mine down to about those specs with my Double tube Disco it seems like it will never need another fill!
Good job ;D
William
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Hmm, interesting to see the varying results. I played with a lighter spring and PA from a Challenger and didn't care for the results. I ended up cutting a couple coils, (don't recall now how much), off the factory Disco spring and going back to the factory end cap with no PA. Now, with 18.1 gr. JSB's, I'm getting 18 shots that start and end at 730fps. Accidentally threw away the paper with the chrony results, so can't say exactly what the shot string was.
Seems like I should be getting more shots at that velocity, but maybe not.
I'm wondering if clipping another coil or more off, and installing a PA made from a screw and rivet, would be of any benifit? Are there other things I should be looking at to make the gun more effecient?
Accuracy's fine, so don't want to mess that up...
Ron.
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Would a 2240 hammer spring work in a disco with a PA? Or would it be way too light?
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Hmm, interesting to see the varying results. I played with a lighter spring and PA from a Challenger and didn't care for the results. I ended up cutting a couple coils, (don't recall now how much), off the factory Disco spring and going back to the factory end cap with no PA. Now, with 18.1 gr. JSB's, I'm getting 18 shots that start and end at 730fps. Accidentally threw away the paper with the chrony results, so can't say exactly what the shot string was.
Seems like I should be getting more shots at that velocity, but maybe not.
I'm wondering if clipping another coil or more off, and installing a PA made from a screw and rivet, would be of any benifit? Are there other things I should be looking at to make the gun more effecient?
Accuracy's fine, so don't want to mess that up...
As always, the question is: "What do you want to use it for?"
Starting and ending at 730 fps means your maxing out velocity at about 760 (assuming 4% spread). That is a lot more power over the full shot string than what I described in the original post. Anywhere from 5-10% additional energy (if my math is correct). As always, more energy means more air.
I imagine you could easily set a goal and meet it by detuning and using a PA to bring it back up to your goal.
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Would a 2240 hammer spring work in a disco with a PA? Or would it be way too light?
It's all about physics. You could use a lighter spring, or a lighter hammer, or both, or a heavier spring with a lighter hammer. You find guys using all kinds of combinations.
It all really just comes down to f=ma
However you get there is up to you. Other guys could maybe chime in about specifics. I've been happy with cut stock spring. Tried a heavier spring and didn't like it so much.
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Thanks William,
I think my next thing will be a Blaster stock especially after seeing yours!
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If I get time today I think I'll set up the chrony and shoot a string. I accidentally threw out all my notes, but there was something about the shot string that I wasn't happy with, just can't recall now. I had also tried a lighter spring and a PA out of a challenger. If I recall correctly, even down in the 600 range, I wasn't getting any more than about 20 shots. Then I somehow managed to screw up the PA so it won't screw in or out. Pulled all that off, clipped the original spring, and called it good.
I posted a thread about it, and I recall someone said it didn't sound like my Disco was shooting efficiently.
Guess I can either leave it be, or start from scratch again...
Ron.
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Can get a 30-40 shot string (under 4%) with a Discovery at about 20 foot pounds (call it 19-20), and there is an added bonus: using 1/2 the air per shot certainly makes it a good bit quieter. All in all, 20 foot pounds well suits the Discovery.
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I clipped 2 coils off my stock spring and took a few shots over the chrony but it gave me readings in the 950's so I stopped because light was fading and was standing too close to my chrony to avoid shooting it. Theres no way It shoots that hot. Roughly what setting will get me 30-40 shots at 20fpe? I would be thrilled with them numbers!
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Should I try turn the screw in until it won't cock and then back it off a couple turns and shoot a string? Is this just a trial and error process because everyone's springs will vary after they clip coils off?
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Should have been clear: a .22 Discovery.
In my case:
Lighter striker spring (about 2 1/2 coils cut from a standard spring).
Striker weight reduced by about 20-25%.
Power adjuster in order to set the spring tension.
Ends up averaging 19.4-20.2 foot pounds (depending on pellet weight) at 4% (the heavier pellets end up earning BOTH a little more energy and a few more shots per 2K-1K fill).
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Should have been clear: a .22 Discovery.
In my case:
Lighter striker spring (about 2 1/2 coils cut from a standard spring).
Striker weight reduced by about 20-25%.
Power adjuster in order to set the spring tension.
Ends up averaging 19.4-20.2 foot pounds (depending on pellet weight) at 4% (the heavier pellets end up earning BOTH a little more energy and a few more shots per 2K-1K fill).
I'm thinking that by lightening your striker weight, you've gained a big advantage over me. I'm getting something like 21 foot pounds with the 18.1 grain pellet, but only for 18 shots. That's with a clipped factory spring, and everything else stock.
Ron.
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This is the string I just shot with cphp 14.3's. I didn't use any preload on the spring just clipped 2 coils off. Shot from 2000psi down to about 900 so it seems I will get about 20 shots. Will I benefit from shortening the spring more or adding tension with the PA?
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I just shot this string. I would call it my medium range' 14.3cphp 2200 psi fill a new full length spring and a new power adjuster
I got a new valve and made the exhaust hole .160 and angled the bottom of it back a little at the bottom of hole. I then took fine sandpaper and cleaned out the tp a little
845.2
860.5
853.2
863.9
858.8
866.4
876.4
875.6
873.0
882.0
890.0
887.2
886.0
888.1
887.2
881.2
880.6
881.1
874.2
856.0
859.5
843.3
Ending at 1200psi
Like I said this would be my medium setting meaning I can add or decrease tension and gain more shots or more power
Tom
Is this a good string?I would like to compare to others
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This is the string I just shot with cphp 14.3's. I didn't use any preload on the spring just clipped 2 coils off. Shot from 2000psi down to about 900 so it seems I will get about 20 shots. Will I benefit from shortening the spring more or adding tension with the PA?
Justin,
Your just so close to being there it isn't funny! To get 20 shots like you are showing at that FPS it pretty darn good for a Disco. If you want less power and more shots lower the fill and ease off the spring a little at a time, you may not have to cut the spring.
Personally I would leave it alone and drop the fill pressure a little very little.
Wish my stock Disco did what yours is doing at them settings ;D
William
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Ok, I don't know where I got the 730 fps, and I don't think my disco is very efficient, I dunno. Here's today's shot string, starting with 2,000psi per the pumps gauge. The gun's gauge is reading higher at that fill.
1)711.7 9)712.8 17)712.3
2)708.5 10)715.0 18)703.2
3)715.2 11)715.0 19)697.7
4)708.0 12)717.2 20)691.9
5)711.3 13)716.6 21)685.9
6)712.8 14)715.1
7)711.6 15)713.8
8)713.1 16)710.5
I can live with this, but it sure seems like at this velocity, I should be getting a lot more shots per fill. What do you guys think? Is there something else I should be looking at? It's not blowing air out the bolt, and it holds air forever.
Ron.
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Thanks William, I will try dropping the fill pressure a bit and see if that tightens the numbers up some. Then I'll just shoot it and shoot it and shoot it... :D
Martis, that to me looks like a very consistent shot string, I am still learning how to "read" shot strings but I don't think there is anything wrong with your Disco. What weight pellets did you use to chrony?
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Thanks William, I will try dropping the fill pressure a bit and see if that tightens the numbers up some. Then I'll just shoot it and shoot it and shoot it... :D
Martis, that to me looks like a very consistent shot string, I am still learning how to "read" shot strings but I don't think there is anything wrong with your Disco. What weight pellets did you use to chrony?
Those are with the 18.1 grain JSB's. They hit really hard, and I'm pretty happy. I'm just thinking maybe there's an air leak or something somewhere.
If you showed me this shot string and said this is what an average Disco does, I'd still buy it in a heartbeat, but if others are doing better, and I can improve mine, I wouldn't mind playing with it.
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Thanks William, I will try dropping the fill pressure a bit and see if that tightens the numbers up some. Then I'll just shoot it and shoot it and shoot it... :D
Martis, that to me looks like a very consistent shot string, I am still learning how to "read" shot strings but I don't think there is anything wrong with your Disco. What weight pellets did you use to chrony?
Those are with the 18.1 grain JSB's. They hit really hard, and I'm pretty happy. I'm just thinking maybe there's an air leak or something somewhere.
If you showed me this shot string and said this is what an average Disco does, I'd still buy it in a heartbeat, but if others are doing better, and I can improve mine, I wouldn't mind playing with it.
Its hard to say what an average string is on a Disco, seems like the newer ones have a stronger spring than the older ones do, mine new 2 years ago or so, was in the mid High 700 FPS range with 20 shots or maybe a little more. Any Disco that is pretty much out of the box with the older slightly weaker original hammer spring will be in the 760-780 FPS range with 20 - 25 shots per fill. The newer ones that somehow got the stronger spring on the hammer are around 900 FPS and only 10 - 12 shots per fill.
A good tuned disco for 15 shots is going to be pushing 15.9 JSB's at 880 FPS or a little higher. If it is getting 25 shots its around the 700 FPS mark as mentioned above. If it is getting 30 to 35 shots it is tuned at around 625 FPS.
You can get a Disco to shoot good in about any FPS depending on pellet used, but my Disco's prefer 15.9 grain JSB's at 825 to 940 FPS and will stack pellets under dimes all day long at 40 yards,,, well sometimes,,, lets not kid anyone here, not even the best shooter is that good at 40 yards, if so prove it,,, then I make offer $$$ for gun lol.
My Disco's will shoot any and all JSB's almost perfect every time no matter the weight, but the 15.9's are the best at 920 FPS for 25 to 30 shots and double tubed, but I am shooting a 3000 PSI fill, the gun is modified for safety to take a higher fill and is regulated at 1800 PSI.
Food for thought, have you tried the 13.43 grain Domed JSB's? they sometimes out shoot anything I have tried in a Disco!
The Disco, one of the best little guns around ;D
Boys they aint nuttin you can't do with a Disco, from pesting flies to killing hogs with a modded .30 cal barrel on it :o
Just pick your pot and a Disco can fill it ;D
William
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MArtis 1:
Pretty good shot count. Do think you could get another 4-6 shots.
IF your run from #12 to #20 is acceptable, then you would be able to start at 685-688 and work up at the start...which could amount to 4-5 shots at the front end of the shot count.
Thing is, to do that, would either have to:
A.Retune the gun slightly to a little lower striker spring tension in order to stay at a 2000psi max fill pressure and gain those early shots.
B.Leave the setting alone and fill to more than the recommended 2000psi (lets say to 2100-2200psi), testing along the way until the velocity reads about 685 for the first shot.
C.Lighten the weight of the striker (which decreases the force of the hit to the valve...like choice A...but also tends to save a little air in the process).
Persoanlly, I tend to stay at or below 2K just to keep to one of the nice concepts of the rifle and go with either A or C. Others here fill to 2.1-2.2K. Tempting in your case as you would have to do NOTHING to the rifle.
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Ribbonstone,
I think that of the options you presented, I'd go with lighter spring tension. For that, I'd have to clip another coil off the spring and install a PA, which I already have parts for.
I'd be afraid of pumping it up any further because now I'm pumping it to 2,000 psi per the Benji pump's gauge, which puts the Disco gauge just into the red. As I'm not sure which gauge is correct, I don't want to go any higher.
Lightening the striker is something I have no idea how to do, so that's out too. ;)
I did try all the other weights of JSB pellets, except for the 15 grainers that everyone seems to find best in their Disco's. That's the one weight that didn't come in the sampler pack. If I recall correctly, most of them shot fairly well in my gun, but the 18's were the most consistent when I moved out to 50 yards.
Actually, the second best pellet, by a very, very, narrow margin, were the Crosman 13grain domes. If and when I can con the boss into letting my buy a .25 cal marauder, I'm thinking of de-tuning the Disco way down and shooting just the Crosmans as a back yard gun. As "back yard friendly" as the Disco is now with the 5" TKO, I can only imagine what it would be like shooting a 13 grain pellet at around 500 fps...
Ron.
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That would likely do it, but your max. speed will also likely be a little lower...maybe losing 10fps. Not a significant amount. Considering the small amount of change you want, could just grind both the ends a bit and end up just a touch shorter.
Noise level (with or without an LDC) is more proportional to air use per shot that anything else...so low speed guns using a small "blip" of air per shot are a lot quieter than the same rifle using a big "burrrrp" of air per shot.
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I decided to put my chrony on a tripod so I don't have to stand so close to make sure Im shooting over the darn thing. And I can do some accuracy testing at the same time! My chrony manual said for the best results keep the muzzle 10 feet from the chronograph though I think that's for PB's? Anyway I got better results this time using JSB 18.1's
1) 736
2) 738
3) 737
4) 741
5) 742
6) 744
7) 745
8) 746
9) 744
10) 756
11) 753
12) 747
13) 752
14) 746
15) 745
16) 744
17) 740
18) 736
I started at 2000psi and after 18 shots I hit 1000 my 19th shot was 725fps I think Im happy with this for now it seems pretty consistent but I wouldn't mind a few more shots per fill. So If I filled to say 2100psi my first shots will be slower?
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Excellent shot count.
Yeah..adding more pressure would likely result in lower speeds at first.
All non-regulated PCP's shoot a kind of flat topped bell curve, so adding pressure would likely push it to the up-slope and shooting to lower pressure would move it to the down slope of the curve.
As it is now, you are starting and ending still on the 1% plateau.
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Thanks Ribbonstone, with an ES of 20fps I should get 18 shots with just a little POI difference at 50 yards? I'll have to see what Chairgun has to say about it :D Will different pellets change the ES or just the average velocity?
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See this is exactly what I'm talking about. Justin's gun is getting 18 shots with the 18 grain pellets that are a good 30 fps faster than mine for the same shot count and same pellet. I don't know if that's just the normal difference between two guns, or if mine's dumping air some place.
I think at least for now, I'll just leave my gun the way it is.
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See this is exactly what I'm talking about. Justin's gun is getting 18 shots with the 18 grain pellets that are a good 30 fps faster than mine for the same shot count and same pellet. I don't know if that's just the normal difference between two guns, or if mine's dumping air some place.
I think at least for now, I'll just leave my gun the way it is.
Every little aspect of each gun makes a difference in shot count, FPS and POI.
One barrel a little tighter than the other, TP ports size, hammer preload, hammer weight and spring power. Is your gauge correct in PSI or maybe some leakage of air when shooting.
I had one barrel that shot 875 FPS and all I did was stick another new barrel on the gun and that barrel shot 800 FPS. If a pellet is too tight it will cause extra friction down the barrel and slow it down. Heavy pellets will sometimes give you more shots and sometimes lighter pellets will give you less shots but more speed, why? A lighter pellets seems to allow more air to escape faster due to it not holding back on the pressure, at least thats the way I see it.
You need to experiment with a good Chronograph and a preload adjuster as well as air pressure fills.
Below is something for you to read, not all chronographs are accurate, you cannot compare your FPS to someones unless they are lined up and shooting over them both at the same time.
Chronograph Accuracy
Any chronograph that relies on sunlight to achieve a
velocity reading is governed by the amount of sunlight
that is received by the unit. Since sunlight is an
electromagnetic radiation2
(EMR) source of Visible,
Infrared (IR) and Ultraviolet light (UV, among others,
that changes with atmosphere concentration and
density as well as it’s angle (time of day). Variables in its
power and composition exist thus affecting the read out
of these chronographs. To put it simply, if your
chronograph relies on sunlight, expect variable results
from day to day and sorry to say hour to hour. The
read-outs can vary up to 30fps when a cloud simply covers the sun.
You may also experience sporadic readouts before 10am and after 3pm.
https://www.precisionshooting.com.au/wp-content/uploads/2014/02/chronographaccuracy.pdf (https://www.precisionshooting.com.au/wp-content/uploads/2014/02/chronographaccuracy.pdf)
So don't get upset of a few FPS 20 to 30 FPS means nothing sometimes, heck yours may be faster than you think....
William
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With your shot string being so consistent It doesn't seem like your guns leaking Ron, I would think your velocity and POI would be off a lot from shot to shot if say your bolt o ring was bad or TP wasn't sealed up. I don't think theres any specific thing to do with these Discos to achieve a specific tune setting you may just have to tinker with a PA until you get to a Velocity/shot count you like. I have an extra 10-32 screw if you would like it also have an extra rivet piece you can use for a spring guide just let me know. Also as Ribbonstone and William have said, you can try different starting fill pressures but for more velocity you may need more tension on the spring? You could get a new stock Disco spring and try cutting a little off at a time until you get to a desired fps?
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I am wondering if anyone saw the string i posted earlier in this thread. If interested my mod is in my gun list.And the new mod is in the thread if anyone is interested tomorrow I will post a picture of the pa and spring I am using
Discos Rock
Tom
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Thanks guys!
As to chrony accuracy, I have my doubts about the consistency of mine, as it's inexpensive and finicky. With pellets, the only way it'll give a reading is if I'm using it in full shade, and with the plastic sun shades off. Also, in working up loads for my 7mm-08, it was giving me wild velocity fluctuations that just didn't make sense considering the loads I was shooting.
I have the bolt and rivet to make a PA, I'm just avoiding tearing into it again...
One thing that bugs me about this particular gun, is that the barrel doesn't line up well with the receiver. By that I mean that in order to zero the scope, I had to install a second barrel band and twist the barrel to the left a ways. It's enough that you can see that it's not centered over the air tube. I'm wondering if I can remove and re-install the barrel and have it straighter? I've never removed the barrel, so I don't know what's involved...
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Ron,
Your barrel may have a little bend to it, or the receiver is not bore perfectly in line, it only takes a couple thousands to be noticeably off at the other end.
I have bent a barrel until it was correct, I don't recommend it if you are not sure what you are doing or if that is the problem!!
Putting a Spring adjuster in is pretty simple, you just have to remove the rear plug which is 2 screws i believe. then add what you want in spring and guide, slip the rear plug back on and screw in the 10-32 screw....
William
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William,
As my rifle groups very nicely, I will probably leave the barrel alone and just not look too closely at it. ;)
I ordered the PA and spring from a challenger and installed it for awhile. I eventually removed it because I just couldn't get it to do what I wanted and somehow the threads eventually bound up on it.
I did pick up a 10/32 allen head bolt, and have a few pop rivots if I decide to use the factory spring, (cut shorter), and a PA.
Come to think of it, I think I have a spring from a Challenger and one from a 2260. I think I ordered the 2260 spring, but the Challenger PA came with a spring too. I have two lighter springs. The lighter of the two was silver and the other black. I tried installing the silver spring, but with the PA all the way in, it was shooting down around 500 fps. Couldn't hardly hear the gun go off, and the shot count was so high I didn't even bother running it down to 1,000 fps. Be a fun, strictly back yard gun, but not practical overall.
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I have a spring that I think came from a 1377 I may try in my disco next time I have the stock off, I think its probably a bit lighter than the disco but not as much as a 2240 spring
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I try to think in terms of percentage when it comes to velocity variations/shot strings in order to keep a more level playing field between 600fps airguns and 900fps airguns.
But I think for the 18 shots /ES 20 you get, the major accuracy factors are NOT the velocity variation. A few MPH or wind change or wind direction change (or both) are the most likely suspects.
LAst time I had the Discovery out, managed this (shooting the last of a box of out-of-date 16gr. pellets, but it's pretty close to 15.9gr. JSB's)
(http://i157.photobucket.com/albums/t50/ribbonstone/Disco/037bd439-2180-4204-a2ab-b3af05d1a206.jpg) (http://s157.photobucket.com/user/ribbonstone/media/Disco/037bd439-2180-4204-a2ab-b3af05d1a206.jpg.html)
It likes the 15.9gr. JSBs a bit better:
(http://i157.photobucket.com/albums/t50/ribbonstone/Disco/3a308a6f-0b69-4afd-9476-c67148abb660.jpg) (http://s157.photobucket.com/user/ribbonstone/media/Disco/3a308a6f-0b69-4afd-9476-c67148abb660.jpg.html)
Not that the JSB's really bave a better 4% shot count, but they gave a much better 1% shot count. For about 17-18 shots, they stayed inside 1% variation (7-8fps).
BUT the important part concering your question is this: I CAN"T TELL THE DIFFERENCE ON PAPER. If I limit my longer range shooting to the 1% area of the shot count, get about the same results (average of groups) as when I stick to the 2% or 3%. The 4% does show up a bit as a few low shots, but even that doesn't exclude it from hunting at 40-50yards.
At 50 yards, the barrel is more of a limitation than the vel. variation. Never have gotten that barrel to average tiny groups, more like 3/4" at that range under great conditions. But that's OK by me, I'll normally limit myself to about 40-45yards, and it works as well as the expensive rifles at that range.
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William,
As my rifle groups very nicely, I will probably leave the barrel alone and just not look too closely at it. ;)
I ordered the PA and spring from a challenger and installed it for awhile. I eventually removed it because I just couldn't get it to do what I wanted and somehow the threads eventually bound up on it.
I did pick up a 10/32 allen head bolt, and have a few pop rivots if I decide to use the factory spring, (cut shorter), and a PA.
Come to think of it, I think I have a spring from a Challenger and one from a 2260. I think I ordered the 2260 spring, but the Challenger PA came with a spring too. I have two lighter springs. The lighter of the two was silver and the other black. I tried installing the silver spring, but with the PA all the way in, it was shooting down around 500 fps. Couldn't hardly hear the gun go off, and the shot count was so high I didn't even bother running it down to 1,000 fps. Be a fun, strictly back yard gun, but not practical overall.
The 10/32 screw is what I have in my one Disco, it is modded for a 3000 PSI fill and I have it cranked up to full power and 920 FPS wiith 15.9 JSB's. I think I get about 25 to 30 shots between 3k and 1800 PSI. I do turn it down when the Grand Children come to visit so they can shoot and shoot and shoot, gosh at 600 FPS that thing never runs out of air!
This has been a really good thread for everyone, you all have showed a lot of details in setup for shot count accuracy and power for a good medium tuned gun. Even some of you have some higher FPS's that are really great on shot count.
Thanks everyone for a great time, the fun that comes from a Disco can never be beat ;D
William
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I almost hate to ask, as it just sounds like a road I shouldn't be headed down, but how does one mod a Disco to safely handle a 3,000 psi fill?
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I almost hate to ask, as it just sounds like a road I shouldn't be headed down, but how does one mod a Disco to safely handle a 3,000 psi fill?
You change the 3 screws that hold the valve in-place which are 8-32 to 3 high tensile strength 10-32 screws, you have to remove the valve and have the screw hold drilled a little out and taped for the 10-32 ones. You may can buy a complete valve from Norm at Discos R US that is already setup for the 3k fill.
The D.P.V. (Disco Power Valve) Valve is made for a 3000 PSI fill. http://discosrus.net/disco/ (http://discosrus.net/disco/)
Contact Norm and he should be able to take care of it if you want too fill higher, you can just modify your valve if you want! Best to let someone do it that is experienced! I tried and messed up a valve...
The weakest point on a Disco is the 3 valve bode 8-32 screws, changing those to a bigger one increases the Safety margin a good bit.
William
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I almost hate to ask, as it just sounds like a road I shouldn't be headed down, but how does one mod a Disco to safely handle a 3,000 psi fill?
You change the 3 screws that hold the valve in-place which are 8-32 to 3 high tensile strength 10-32 screws, you have to remove the valve and have the screw hold drilled a little out and taped for the 10-32 ones. You may can buy a complete valve from Norm at Discos R US that is already setup for the 3k fill.
The D.P.V. (Disco Power Valve) Valve is made for a 3000 PSI fill. http://discosrus.net/disco/ (http://discosrus.net/disco/)
Contact Norm and he should be able to take care of it if you want too fill higher, you can just modify your valve if you want! Best to let someone do it that is experienced! I tried and messed up a valve...
The weakest point on a Disco is the 3 valve bode 8-32 screws, changing those to a bigger one increases the Safety margin a good bit.
William
Thanks!
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I almost hate to ask, as it just sounds like a road I shouldn't be headed down, but how does one mod a Disco to safely handle a 3,000 psi fill?
You change the 3 screws that hold the valve in-place which are 8-32 to 3 high tensile strength 10-32 screws, you have to remove the valve and have the screw hold drilled a little out and taped for the 10-32 ones. You may can buy a complete valve from Norm at Discos R US that is already setup for the 3k fill.
The D.P.V. (Disco Power Valve) Valve is made for a 3000 PSI fill. http://discosrus.net/disco/ (http://discosrus.net/disco/)
Contact Norm and he should be able to take care of it if you want too fill higher, you can just modify your valve if you want! Best to let someone do it that is experienced! I tried and messed up a valve...
The weakest point on a Disco is the 3 valve bode 8-32 screws, changing those to a bigger one increases the Safety margin a good bit.
William
i was thinking of buying this but isn't $85 sort of expensive? I'm pretty sure the valve from crosman is $15 and the only modification he does as far as i can tell is retap it for bigger screws.
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I almost hate to ask, as it just sounds like a road I shouldn't be headed down, but how does one mod a Disco to safely handle a 3,000 psi fill?
You change the 3 screws that hold the valve in-place which are 8-32 to 3 high tensile strength 10-32 screws, you have to remove the valve and have the screw hold drilled a little out and taped for the 10-32 ones. You may can buy a complete valve from Norm at Discos R US that is already setup for the 3k fill.
The D.P.V. (Disco Power Valve) Valve is made for a 3000 PSI fill. http://discosrus.net/disco/ (http://discosrus.net/disco/)
Contact Norm and he should be able to take care of it if you want too fill higher, you can just modify your valve if you want! Best to let someone do it that is experienced! I tried and messed up a valve...
The weakest point on a Disco is the 3 valve bode 8-32 screws, changing those to a bigger one increases the Safety margin a good bit.
William
i was thinking of buying this but isn't $85 sort of expensive? I'm pretty sure the valve from crosman is $15 and the only modification he does as far as i can tell is retap it for bigger screws.
The price on that valve it reasonable, takes a lot of machine work to make those valves.
You can use your present factory Valve, it is just not easy to drill and tap for the 10-32 screw, you can do it yourself but you need to be very careful as not to go very deep.
The hole needs drilled out but it is very little drilling needed. What you do is find the screws (I recommend getting them from Norm at Discos R US) they must be the correct high tinsel strength and the correct length, which you can do yourself, then you need 2 10/32 taps, 1. Regular tap to just start the threads and the 2nd one is a bottom tap to finish it up. It is better to let someone do it in a vise and a mill machine to keep it straight. If you go too deep you put a hole in the bottom and into the valve air chamber then you need a new valve.
Just buy a Crosman valve and send it to Norm and let him do it, he doesn't charge much. Or a machine shop, but they will charge about what a D.P.V would cost.
William
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I do believe there are additional mods on a DPV than just the retaining screws. I cant quote exactly, but I believe he bored out a bunch. Since it is his business, I wouldnt expect him to share specifics, but he might.
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I do believe there are additional mods on a DPV than just the retaining screws. I cant quote exactly, but I believe he bored out a bunch. Since it is his business, I wouldnt expect him to share specifics, but he might.
I believe that valve is made from a Crosman valve. Either way, the Crosman valve will do just fine if you want to mod for more power. Drill out the TP port, Barrel Port and Valve Port. Make the hole bigger in air gauge block to allow more air flow to the valve or use a Prod gauge block.
Very cheap to do as far as cost and once your done you have a very powerful Disco capable of shooting 15.9 grain pellets at 950 fps with no problem. Or turn it down for plenty of lower power shots.
William
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Am I understanding right that with the change in the three screws you can safely fill the standard Disco tube to 3000 psi?
Ed
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Am I understanding right that with the change in the three screws you can safely fill the standard Disco tube to 3000 psi?
Ed
Yes you are correct, changing it to the Proper Tensil strength screws will allow you to safely fill to 3000 PSI. I have both my Disco's setup that way.
There is a thread here on the GTA about doing the modification...
William
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The DPV valve is a highly modified factory Disco valve and being able to get 30 great power shots in the low to high 40 FPE will not be easy to match.
JSP Monsters 25.39 gr. at 49.46 with 30, shots is pretty amazing from a Disco
Norm
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The DPV valve is a highly modified factory Disco valve and being able to get 30 great power shots in the low to high 40 FPE will not be easy to match.
JSP Monsters 25.39 gr. at 49.46 with 30, shots is pretty amazing from a Disco
Norm
Just wanted to say hello Norm, how have you been? Thank you for posting the valve info. Those are some outstanding numbers thats for sure. Yes I still have both my custom Discos I got from you and I love the 920 FPS 15.9 JSB dime size groups all day at 40 yards. I get 25 shots on the single tube and around 35 shots on the double tubed one. Everyone should have a Disco or two in the house, I think it should be a law that you have to own one, it is a great little rifle to do anything you want with it!
Thank you,
William
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A big hello to you William
Yes a good Disco, and it is not too difficult to make them extremely good should be a must for everyone.
My little Disco FTs are going to be a winner! You may just need one. ;D ;D ;D
Norm
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A big hello to you William
Yes a good Disco, and it is not too difficult to make them extremely good should be a must for everyone.
My little Disco FTs are going to be a winner! You may just need one. ;D ;D ;D
Norm
LOL, I have been lucky so far, the wife has not caught on yet, she just thinks I keep dressing up the same gun all the time, what a shame because I have 7 total counting 2 springers.
Boy if I get caught I am not going to be feeling well for a long time lol
William
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I almost hate to ask, as it just sounds like a road I shouldn't be headed down, but how does one mod a Disco to safely handle a 3,000 psi fill?
You change the 3 screws that hold the valve in-place which are 8-32 to 3 high tensile strength 10-32 screws, you have to remove the valve and have the screw hold drilled a little out and taped for the 10-32 ones. You may can buy a complete valve from Norm at Discos R US that is already setup for the 3k fill.
The D.P.V. (Disco Power Valve) Valve is made for a 3000 PSI fill. http://discosrus.net/disco/ (http://discosrus.net/disco/)
Contact Norm and he should be able to take care of it if you want too fill higher, you can just modify your valve if you want! Best to let someone do it that is experienced! I tried and messed up a valve...
The weakest point on a Disco is the 3 valve bode 8-32 screws, changing those to a bigger one increases the Safety margin a good bit.
William
i was thinking of buying this but isn't $85 sort of expensive? I'm pretty sure the valve from crosman is $15 and the only modification he does as far as i can tell is retap it for bigger screws.
85.00 is cheap...I bought a Cothran Machine PowerHouse valve for 120.00 and it is a BEAST!!!!!
http://www.cothranmachine.com/WhatNew.HTML (http://www.cothranmachine.com/WhatNew.HTML)
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yeah I guess if the valve is highly modified $85 is more than reasonable... I thought it was simply a stock valve but retapped for bigger screws. 30 shots at 40 fpe.. wow! is that with the standard disco airtube or a bottlefed one? If its the first one i will definitely have to pick one up..might be awhile though since i'll need to sell my pump for a scuba setup since pumping to 3k psi sounds like some pain
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I dunno. Seeing how much power there is in a 3,000 psi scuba setup and what kind of very immediate damage can be done at that pressure when something isn't built or serviced correctly, I'd say $85 for a professionally customized part is a small price to pay. I'm not a machinist, and I think for me to try and modify a part to take that kind of pressure would be foolish. With that in mind, I think if I ever have a hankering to ramp up my Disco in such a manner, I would probably just box it up and send it off to Norm.
Just sayin' ;)
Ron.
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yeah I guess if the valve is highly modified $85 is more than reasonable... I thought it was simply a stock valve but retapped for bigger screws. 30 shots at 40 fpe.. wow! is that with the standard disco airtube or a bottlefed one? If its the first one i will definitely have to pick one up..might be awhile though since i'll need to sell my pump for a scuba setup since pumping to 3k psi sounds like some pain
Bottlefed.