detune and increase shot count Discovery .22 by cutting spring but no chrony

[stanley1131]

I heard the easiest way to detune  and increase shot count for the discovery  is by cutting a bit of the spring but  i dont have a chrony so i wont know if i'm screwing up the power curve. Has anyone done this to a disco and recorded the results? I have no specific goal but right now my disco only get 15 shots from 2000psi to 1200 so any increase in shot count will be helpful.

[Rocker1]

You need some preload on the hammer, It would be best to change springs or make or buy a power adjuster. A power adjuster is not hard to make on a disco.  David

[stanley1131]

wouldn't more preload on the hammer give me more fps but less shot count?I always thought power adjusters were more for increasing the power. I need more shots per fill not fps

[Rocker1]

You can let off the spring pressure.  It works both ways sir.    One of the best mods you can do.  David

[stanley1131]

Okay ill get a power adjuster to play around with but the main issue is i dont have a chrony so  i wont know what kind of fps and how consistent the shot strings are at a given setting. I was hoping cutting the spring would be more precise such as cut one coil = x fps reduction. Also which power adjuster do you recommend? I saw the diy vid where you use  a 10-32 screw to add preload but wouldn't that only be useful to increase fps? If you back the screw all the way out it would be back at stock

[GLPalinkas]

I get what you are trying to do. I book marked a couple of posts so that when my Disco gets here I could do the same.

Here is the info you wanted.

http://www.gatewaytoairguns.org/GTA/index.php?topic=77272.0

[Ribbonstone]

Have shown targets like this several times.

You will not know how fast it is shooting, but you can figure out where it’s shooting as consistently as it can.

Until you buy a chronograph, it’s better than just guessing.

Better at longer range, but even short range (20-25yards) can work to spot the trend.

Target like below, 3 or 5 shots per dot, NO SCOPE ADJUSTMENTS during shooting. Shoot each target in order, left to right.


Idea is that velocity changes show up as trajectory changes.  Generally, slower hits lower.  We won’t know what that velocity is, just where it is fastest.




Can actually spot the rise and fall in the above target, but can make it more obvious by pasting the targets closer together.



Connecting the target centers with a line:



Which tells me that the targets from #2 to about #6 is where the “sweet spot” lives  for this tune-setting. Still don’t  know how fast, but would at least know where the rifle was shooting  most consistently and for about how many shots.

[zaphod621]

A power adjuster will not reduce the tension on the spring, it can only go from stock or higher. I did not cut the spring on mine I drilled out the end cap to reduce spring tension instead. I went .30" deeper so the spring tension is reduced but all that really does is lower my fill pressure on the bell curve. The best way of increasing shot count is to use a more restrictive transfer port. I bought one from Crosman that's for the Challenger rifle and I drilled it out to .110" and give the power adjuster 8 turns in of preload and my shot count went up to 40 shots within 4% of my peak with an average speed of 780fps with JSB 14.3 pellets @ just over 19fpe. I can get more shots if I back my adjuster off to zero but I like the power level its at now and 40 shots is pretty darn good and my bell curve is nice and flat like this as I am getting 18 shots within 2% right in the middle of the string. It makes my first generation .22 Disco the gun I always wanted it to be. Hope this helps.

[Rocker1]

Mine do reduce the spring tension and most I have seen will.  David

[stanley1131]

I get what you are trying to do. I book marked a couple of posts so that when my Disco gets here I could do the same.

Here is the info you wanted.

http://www.gatewaytoairguns.org/GTA/index.php?topic=77272.0

wow thanks thats the exact information i was looking for, I'm going to cut 1-2 coils in 1/2 coil increments and see what happens... I wish i got the info when i first got my disco, would have saved me a ton of pumping

[tjcib]

I cut three full coils off the stock spring. Used a pop rivet as a spring guide with the 10-32 screw. Getting 35 shots per fill at 680 fps using JSB 18s

[Tommy]

When I did this I did not have a chrony. I just read alot and decided what I was going to do When I got the chrony I was right where I wanted to be. When I screw in my PA to coil bind then out 1/2 turn I get my power then when I take out PA I get my plinking setting. Glad I could help.
I still think Disco should have their own sticky as they are very popular and new owners need a place to make their gun what they want
Tom



DISCOS RULE

[stanley1131]

What did you guys use for a spring guide and about what length should it be? In the youtube vid i saw the guy using a screw from a scope mount that he filed down, is there anything i can buy that'll be smooth?

[tjcib]

What did you guys use for a spring guide and about what length should it be? In the youtube vid i saw the guy using a screw from a scope mount that he filed down, is there anything i can buy that'll be smooth?

I used a pop rivet...I hammered out the pin...it's perfectly. I believe it was a 1/4 inch rivet.  But the head fits into the tube cap. Turned the power adjuster to where the gun wouldn't cock, then backed it out to a quarter turn out from no cocking.


Tommy, I think you and I had the "sticky" discussion before. See my signature, I just started to compile info...like last week.

[NickB79]

My Disco was shooting 9.8 gr Winchesters at 960 fps new, but only got 13 shots from 2000-1000 psi.

I cut two full coils off the hammer spring, and velocity dropped to 900 fps, but shot count went up to 22 per fill.

I'm satisfied.