sub 12 ft-lb Disco string-finally looks ok...

sub 12 ft-lb Disco string-finally looks ok...

Joined: May 14th, 2004, 4:11 pm

August 3rd, 2008, 1:01 am #1

After taking Steve from NC advice about achieving a sub 12 ft-lb Disco by reducing the hammer weight and using a lighter hammer spring(2260) I finally have a decent shot string.

Along with the reduced hammer weight and spring I added a Big Ed HDD as well. The Disco has a Mac1 power adjuster that I had turned out 1.5 turns from all the way in.

I started with a 1400 psi fill and ended about 800 psi. As you can see the 1400 was too much to start with but the middle to end of the string looks good to me. I got a 36 shot string that had an ES of 18.4 fps with an average velocity of 779.8 fps. with 7.9 cpls(10.6ft-lb). Once I figure out where to start my fill at I think I am good to go. Next, its an FT stock for the Disco.

705.4 shot-1
700.9
703.4
704.1
713.3
718.5
726.2
719.1
726.8
727.4 shot-10
739.9
750.3
747.9
755.8
748.8
750.8
737.2
750.9
743.1
761.9 shot-20
747.8
761.1
757.3
765.7
771.3
772.2
772.3
762.4
777.3-----------
777.2 shot-30
782.9
774.7
783.2
775.4
774.5
780.4
773.8
775.8
774.8
783.2 shot-40
785.8
772.9
777.3
776.1
783.2
781.2
781.7
779.6
778.0
789.9 shot-50
781.7
777.3
785.9
787.9
784.2
789.7
776.5
778.2
781.0
785.8 shot-60
783.7
771.5
780.8
777.5-----------
770.5
763.4
764.5
763.2
757.9 shot-69


Jeff P
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Joined: November 17th, 2006, 3:51 am

August 3rd, 2008, 1:09 am #2

And amazing that it was done using 600PSI. Believe this is a direction I'd want to go with the Discovery. Perhaps starting at 1200psi would minimize the "warm up" string?
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Joined: October 23rd, 2005, 6:49 am

August 4th, 2008, 9:46 pm #3

After taking Steve from NC advice about achieving a sub 12 ft-lb Disco by reducing the hammer weight and using a lighter hammer spring(2260) I finally have a decent shot string.

Along with the reduced hammer weight and spring I added a Big Ed HDD as well. The Disco has a Mac1 power adjuster that I had turned out 1.5 turns from all the way in.

I started with a 1400 psi fill and ended about 800 psi. As you can see the 1400 was too much to start with but the middle to end of the string looks good to me. I got a 36 shot string that had an ES of 18.4 fps with an average velocity of 779.8 fps. with 7.9 cpls(10.6ft-lb). Once I figure out where to start my fill at I think I am good to go. Next, its an FT stock for the Disco.

705.4 shot-1
700.9
703.4
704.1
713.3
718.5
726.2
719.1
726.8
727.4 shot-10
739.9
750.3
747.9
755.8
748.8
750.8
737.2
750.9
743.1
761.9 shot-20
747.8
761.1
757.3
765.7
771.3
772.2
772.3
762.4
777.3-----------
777.2 shot-30
782.9
774.7
783.2
775.4
774.5
780.4
773.8
775.8
774.8
783.2 shot-40
785.8
772.9
777.3
776.1
783.2
781.2
781.7
779.6
778.0
789.9 shot-50
781.7
777.3
785.9
787.9
784.2
789.7
776.5
778.2
781.0
785.8 shot-60
783.7
771.5
780.8
777.5-----------
770.5
763.4
764.5
763.2
757.9 shot-69


Jeff P
Just love them workning in such low pressure..

BSA Airguns Ultra .22 - Leupold EFR 3-9x33 VX-II
Benjamin Discovery 177 - Leupold EFR 3-9x33 VX-I
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Joined: May 14th, 2004, 4:11 pm

August 4th, 2008, 10:55 pm #4

I took a look at yours to see what kind of spread you were getting. Is the only change that you made was to the hammer spring? I'd like to see what the UK spring looks like. I didn't have good luck with the factory hammer and a lighter (2260) spring.

I ground the hammer down to reduce its weight. I used a 2260 hammer spring for the string above. However the more I shot it my beginning shots dropped in velocity slightly. I had the power adjuster screwed almost all of the way in(1.5 turns out) and maybe the spring began to fatigue? Anyway I went back to the factory spring and cut a few coils off. It is a stouter spring. Now the power adjuster is barely preloading the spring and I'm getting between 30-35 good shots with an average of 785fps with an ES of 24fps. Hopefully it will stay this way.

Jeff P
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Joined: October 23rd, 2005, 6:49 am

August 5th, 2008, 10:10 am #5


Just changed the spring drop-in style..

Here are the springs:

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BSA Airguns Ultra .22 - Leupold EFR 3-9x33 VX-II
Benjamin Discovery 177 - Leupold EFR 3-9x33 VX-I
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Joined: May 14th, 2004, 4:11 pm

August 5th, 2008, 2:44 pm #6

You wouldn't happen to know the wire dia. on the 12 ft-lb UK spring?

Thanks
Jeff P
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Joined: October 23rd, 2005, 6:49 am

August 5th, 2008, 10:30 pm #7


But I will take its measurements as soon as its out of the rifle again.

(Some day later in the week when my US stuff for this model arrives)

BSA Airguns Ultra .22 - Leupold EFR 3-9x33 VX-II
Benjamin Discovery 177 - Leupold EFR 3-9x33 VX-I
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