GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: sr1sws on March 17, 2014, 08:40:23 PM
-
I've had my Disco about a month and did the 3 screw mod on it.
Recently I stumbled across the 'lower link mod' which involves drilling the pivot hole 1/4" forward.
Sounds easy enough to do. Apparently with the link mod, you do not use any of the screws.
Proponents of the link mod say the 3 screw mod promotes velocity variations due to sear drag on the hammer.
Before I tear my Disco apart again and try it, is there any general consensus on which of the two mods is better?
Thanks,
Steve
-
I did both mods and you need to so you can adjust the trigger, the lower link mod as you call it (not sure what it was when i found out about it) works freaking great, trigger pull is a lot easier and a little longer but can be adjusted with the 3 screw mod. Also I replace the little spring with one out of a ball point ink-pin (the one that pushes on the trigger) to make it a lot lighter pull. I did have to take my Dremel and grind off a couple little places on the trigger so as it would pivot enough, you can tell what needs ground or sanded off after you drill the hole and put it in place and try it, be patient it takes a few tries to get it just right and be careful not to over do it and cause an accidental discharge. I guarantee you, that after you do these mods to the trigger you will think you have a Marauder trigger on it. Best thing I ever did. Wish I would have videoed it showing the steps to help others, but look around on YouTube and you will find how to videos.
PS. Don't forget you will more than likely have to do some sanding on the trigger and some of the other parts so they can pivot and move enough for sufficient usage. Wish I had pics of what did, now i dont remember the parts I modified, and it doesnt take much grinding or sanding.
-
Awesome info, thank you!
Steve
-
Awesome info, thank you!
Steve
Your welcome, if you look at my profile you can find some post as to what i did to my Discovery in mods and things, Mine is a 22 cal. took me awhile to get it shooting due to a bad barrel at the muzzle end.
-
Forgive me if I'm not totally getting this mod, but I can't seem to find definitive directions. Is it basically doing only this? And does anyone know if it's a pretty safe mod? Seems easy enough...
(http://i57.tinypic.com/2a4ojtf.jpg)
-
Forgive me if I'm not totally getting this mod, but I can't seem to find definitive directions. Is it basically doing only this? And does anyone know if it's a pretty safe mod? Seems easy enough...
(http://i57.tinypic.com/2a4ojtf.jpg)
You photos match the description I read and is what I'll be trying.
Oh, the 'link' is supposed to be case hardened, so use a Dremel or something to grind through the surface, then center punch and drill (1/8").
While you have it apart, you might want to do the 3 screw mod and shim the parts to reduce lateral play.
Steve
-
Awesome info, thank you!
Steve
Your welcome, if you look at my profile you can find some post as to what i did to my Discovery in mods and things, Mine is a 22 cal. took me awhile to get it shooting due to a bad barrel at the muzzle end.
Thanks, I chased them down. One of your posts mentions polishing the leade... can you comment on how you did that? I have not removed my barrel from the breech block... the grub screw is really tight... guess I should use a little heat (probably a heat gun) - I was afraid to strip the screw head or the allen wrench.
Steve
-
Forgive me if I'm not totally getting this mod, but I can't seem to find definitive directions. Is it basically doing only this? And does anyone know if it's a pretty safe mod? Seems easy enough...
(http://i57.tinypic.com/2a4ojtf.jpg)
Thats is exactly what and how i did mine and yes it is safe, it just makes the trigger easier to pull due to giving you more leverage. But, as i mentioned above once you get it all back in place squeeze the trigger and make sure the trigger and other parts are not obstructed. Yours may not get obstructed, I just laid the plate on and held it down while squeezing the trigger to see if it hit anything.
Oh, I think I had to grind on some of the plastic on trigger and trigger housing frame, but not much at all You may not have too, just try and see.
(http://www.webexpressplus.com/disco/trigger/lowerlink.jpg)
-
K, good info. Thanks guys.
-
Awesome info, thank you!
Steve
Your welcome, if you look at my profile you can find some post as to what i did to my Discovery in mods and things, Mine is a 22 cal. took me awhile to get it shooting due to a bad barrel at the muzzle end.
Thanks, I chased them down. One of your posts mentions polishing the leade... can you comment on how you did that? I have not removed my barrel from the breech block... the grub screw is really tight... guess I should use a little heat (probably a heat gun) - I was afraid to strip the screw head or the allen wrench.
Steve
Do not use any heat, if you dont see anything wrong as mentioned just leave it together. If you have a bar clamp or a clamp you can squeeze the barrel and the pressure tube a little and that will loosen up the screw. Do this only if you have too.
If you have a Dremel, with a small polishing tip or I also used Polishing compound on a tight patch. You need to check and make sure you do not have any metal burrs stick out into the chamber (lead-in) from where they machined in the air port into the barrel, my barrel had a burr sticking down into the pellet chamber, just polish it out or just barely touch it with sand paper then polish it, it doesnt have to be as slick as glass, your just getting out the really bad spots it there are any. I chambered a pellet and pushed it backwards back out of the chamber with a wood dowel rod or cleaning rod and looked for unusual nicks in the pellet.
-
Forgive me if I'm not totally getting this mod, but I can't seem to find definitive directions. Is it basically doing only this? And does anyone know if it's a pretty safe mod? Seems easy enough...
(http://i57.tinypic.com/2a4ojtf.jpg)
You photos match the description I read and is what I'll be trying.
Oh, the 'link' is supposed to be case hardened, so use a Dremel or something to grind through the surface, then center punch and drill (1/8").
While you have it apart, you might want to do the 3 screw mod and shim the parts to reduce lateral play.
Steve
I just drilled mine, go slow and the drill bit will cut through it, its not that hard!
-
Thanks... I did learn the 'bar clamp trick' and found the breech screw was loose... tightened that up.
The other day, I got a 2nd barrel band and located that in front of the breech - had to cut a section out of the sleeve/rear sight base "tube". It was at that time I attempted (not very hard) to loosen the barrel grub screw in the 'breech block'.
Oh further review, before attempting to remove the barrel, should the barrel/breech/receiver assembly be separated from the air tube?... does the transfer port tube extend to the barrel or just into the breech/receiver?
I re-crowned the barrel using the #6 slotted brass screw and valve lapping compound. Forward barrel band is about an inch behind the TKO LDC - tightly secured to the air tube, but the barrel screw barely touches the barrel. Rear barrel band is tight to air tube and barrel.
Overall, the gun shoots OK, but not quite a good as I think it could/should. It seems to like Crosman 10.5g 'brown box' Premiers best. I haven't found a wad cutter that it likes for more than about 2 shots.
I keep looking for something amiss, hence my question on polishing the leade.
I have a Mellonair 'long probe' bolt on order, but if he's really still 12 weeks behind it will be 3 months before that shows up. They are supposed to help with accuracy - cheap enough to try.
Thanks for the tips!
Steve
-
Thanks... I did learn the 'bar clamp trick' and found the breech screw was loose... tightened that up.
The other day, I got a 2nd barrel band and located that in front of the breech - had to cut a section out of the sleeve/rear sight base "tube". It was at that time I attempted (not very hard) to loosen the barrel grub screw in the 'breech block'.
Oh further review, before attempting to remove the barrel, should the barrel/breech/receiver assembly be separated from the air tube?... does the transfer port tube extend to the barrel or just into the breech/receiver?
I re-crowned the barrel using the #6 slotted brass screw and valve lapping compound. Forward barrel band is about an inch behind the TKO LDC - tightly secured to the air tube, but the barrel screw barely touches the barrel. Rear barrel band is tight to air tube and barrel.
Overall, the gun shoots OK, but not quite a good as I think it could/should. It seems to like Crosman 10.5g 'brown box' Premiers best. I haven't found a wad cutter that it likes for more than about 2 shots.
I keep looking for something amiss, hence my question on polishing the leade.
I have a Mellonair 'long probe' bolt on order, but if he's really still 12 weeks behind it will be 3 months before that shows up. They are supposed to help with accuracy - cheap enough to try.
Thanks for the tips!
Steve
Yes, The breech assembly has to be removed from the Air Tube, the transfer port tube goes through the breech and into the barrel, receiver must be removed from the air tube first. If not the transfer port will not allow the barrel to slide out.
My gun in 22 cal loves domed pellets and shoots great now, after a lot of modding, mostly my problem was the bad barrel!
-
Awesome info, thank you!
Steve
Your welcome, if you look at my profile you can find some post as to what i did to my Discovery in mods and things, Mine is a 22 cal. took me awhile to get it shooting due to a bad barrel at the muzzle end.
Thanks, I chased them down. One of your posts mentions polishing the leade... can you comment on how you did that? I have not removed my barrel from the breech block... the grub screw is really tight... guess I should use a little heat (probably a heat gun) - I was afraid to strip the screw head or the allen wrench.
Steve
You should order the stainless steel slotted breech screws from AC Customs --- http://www.accustommods.com/small-parts.html (http://www.accustommods.com/small-parts.html)
They are easier to remove and a whole HECK of lot better to screw in. I got 4 and I have removed them multiple times with any issues.
Joe
-
Overall, the gun shoots OK, but not quite a good as I think it could/should. It seems to like Crosman 10.5g 'brown box' Premiers best. I haven't found a wad cutter that it likes for more than about 2 shots.
I keep looking for something amiss, hence my question on polishing the leade.
I have a Mellonair 'long probe' bolt on order, but if he's really still 12 weeks behind it will be 3 months before that shows up. They are supposed to help with accuracy - cheap enough to try.
Thanks for the tips!
Steve
If you want better accuracy follow the link below:
http://www.tko22.com/info.html (http://www.tko22.com/info.html)
Adding the 2 screws and shimming the barrel bands (very important what he says about angle of the the barrel; you do not want to change this) changed my 25 yard groups from 3/8" to same hole accuracy.
-
The lower link, or transfer bar mod works great, I did not have any problem drilling the hole, did not seem hardened to me. It changes the leverage and helps a lot, plus, you are not compromising the sear engagement like you do when you add the third screw. polish the the parts a bit, switch the trigger spring with a ball point spring and you will be happy. If for some reason you don`t like it, move the pin back to the stock location.
-
Moving the pivot point on the link forward reduces the trigger pull when moving the sear, but increases the travel.... If you replace the coil spring behind the trigger with a lighter one, and make no other changes, you will immediately notice what feels like a 2-stage trigger, first as you compress the coil spring, and then as the link moves the sear which is loaded by the hairpin style spring.... If you install the upper back screw, as you screw it in, you will be tilting the trigger, moving the blade back at the bottom and shortening what you are perceiving as the 1st stage.... Eventually you will have no 1st stage, only the 2nd, harder stage as you begin to move the sear against the hairpin spring.... It is at this point in the movement that changing the pivot point changes the leverage, reducing the effort but increasing the distance the trigger will move during the second stage....
The lower back screw adjusts only the "over-travel" of the trigger (ie how far it moves after the gun fires).... and THAT is the one that can cause sear drag if set too close.... because it doesn't allow the sear to drop enough to completely clear the hammer.... causing erratic velocities.... DON'T SET IT TOO CLOSE OR YOU WILL HAVE PROBLEMS....
The third, front screw, if installed, requires drilling and tappng another hole in the space between the plastic lug and the front of the link lever, so that you can adjust the position of the front of the link lever.... Screwing it in moves the link up, pressing on the front of the sear, moving the back of the sear down and decreasing the engagement.... Taken to the extreme, it makes the gun unsafe as there is so little engagement that the gun will fire if bumped hard (or won't even cock).... If you redrill the link to move the pivot forward, the 2nd stage gets longer, and although the effort is less, you get a "creepy" trigger, which I find unsatisfactory.... You can compenstate by screwing in the third screw and reducing the sear engagement, but that will eventually make the gun unsafe....
So, what is redrilling the link accomplishing?.... It is reducing the 2nd stage pull (a good thing), but it is reducing the sear travel, causing more creep for a given (ie safe) engagement (a bad thing).... Is there a better way?.... IMO, yes, instead of redrilling the link, just reduce the angle between the legs of the hairpin spring about 5 degrees by bending it carefully.... Then you can have a safer sear engagement and yet reduce the weight of the trigger pull during the 2nd stage.... It doesn't take much to drastically change the trigger pull, try it and see.... Use a protractor, or simply draw lines on a piece of paper along the legs of the spring when stock, and then push the legs towards each other until the coils tighten up and the legs are at a slightly tighter angle when relaxed.... The tighter the angle, the less force required during the 2nd stage to move the sear.... Don't go too far, or you may make the trigger unsafe.... mind you it's an easy thing to bend the legs out again to change it....
The above assumes that you have replaced the coil spring behind the trigger blade with a lighter one, or you won't even feel the two stages.... I use a coil spring of the same diameter and length but made from 0.020" wire instead of the stock 0.028" wire, and find it just right.... If you want a really light 1st stage, you can go down to 0.016" wire.... Sometimes I don't even bother with the 3rd (front) screw, just replacing the coil spring, bending the hairpin spring, and installing and adjusting the two rear screws makes for quite a nice trigger, particularly for hunting.... For a target gun, adding the 3rd screw to reduce the sear engagement is nice....
Bob
-
If you bend the spring, does the safety still still have the correct tension?
-
Thanks for the tip on bending the hair spring/sear spring. Sounds easy enough.
I guess the good thing about all of these mods is they are reversible :)
Steve
-
Overall, the gun shoots OK, but not quite a good as I think it could/should. It seems to like Crosman 10.5g 'brown box' Premiers best. I haven't found a wad cutter that it likes for more than about 2 shots.
I keep looking for something amiss, hence my question on polishing the leade.
I have a Mellonair 'long probe' bolt on order, but if he's really still 12 weeks behind it will be 3 months before that shows up. They are supposed to help with accuracy - cheap enough to try.
Thanks for the tips!
Steve
If you want better accuracy follow the link below:
http://www.tko22.com/info.html (http://www.tko22.com/info.html)
Adding the 2 screws and shimming the barrel bands (very important what he says about angle of the the barrel; you do not want to change this) changed my 25 yard groups from 3/8" to same hole accuracy.
Been there, done that. I'm now using 2 bands - one at breech and one ~1" from barrel end. No shims. Rear band is tight to air tube and barrel, front is tight to air tube only. It's better, but I want better still... until I know it's me that's making that pellet go "there" :)
Steve
-
All the hairpin spring does for the safety is keep it from falling out and act as a detent.... You only need to bend the spring about 5 degrees, if you bend it maybe 15 degrees it won't work at all and the safety will fall through the hole and you will have no spring tension to reset the sear.... A little bit changes things in a hurry, the good thing is, it's easy to keep trying until you get the pull you want.... If you haven't got a protractor, draw lines on a piece of paper to start with and after each change so you can compare the angle to what the trigger feels like....
Bob
-
Overall, the gun shoots OK, but not quite a good as I think it could/should. It seems to like Crosman 10.5g 'brown box' Premiers best. I haven't found a wad cutter that it likes for more than about 2 shots.
I keep looking for something amiss, hence my question on polishing the leade.
I have a Mellonair 'long probe' bolt on order, but if he's really still 12 weeks behind it will be 3 months before that shows up. They are supposed to help with accuracy - cheap enough to try.
Thanks for the tips!
Steve
If you want better accuracy follow the link below:
http://www.tko22.com/info.html (http://www.tko22.com/info.html)
Adding the 2 screws and shimming the barrel bands (very important what he says about angle of the the barrel; you do not want to change this) changed my 25 yard groups from 3/8" to same hole accuracy.
Been there, done that. I'm now using 2 bands - one at breech and one ~1" from barrel end. No shims. Rear band is tight to air tube and barrel, front is tight to air tube only. It's better, but I want better still... until I know it's me that's making that pellet go "there" :)
Steve
You may need to start experimenting with the position of your bands. Barrel resonation is a vibration in the barrel that actually cycles up and down the length of the barrel once the gun goes off, and if the barrel is resonating at or near the muzzle when the pellet exits, it is going to do terrible things to accuracy. Changing the position of the bands will change this. I would also consider lapping the entire barrel. I lapped mine, 6 screwed the band, and thought it was gonna shoot great. Much to my dismay, it didn't change a bit until i tried moving the band around and changing how i was loading the barrel with the set screws. Now, about 1.5" forward of the original position, with the screws set right, its a tack driver.
-
You may need to start experimenting with the position of your bands. Barrel resonation is a vibration in the barrel that actually cycles up and down the length of the barrel once the gun goes off, and if the barrel is resonating at or near the muzzle when the pellet exits, it is going to do terrible things to accuracy. Changing the position of the bands will change this. I would also consider lapping the entire barrel. I lapped mine, 6 screwed the band, and thought it was gonna shoot great. Much to my dismay, it didn't change a bit until i tried moving the band around and changing how i was loading the barrel with the set screws. Now, about 1.5" forward of the original position, with the screws set right, its a tack driver.
Any magic formula for determining band position - or is it simply trial and error?
Steve
-
You may need to start experimenting with the position of your bands. Barrel resonation is a vibration in the barrel that actually cycles up and down the length of the barrel once the gun goes off, and if the barrel is resonating at or near the muzzle when the pellet exits, it is going to do terrible things to accuracy. Changing the position of the bands will change this. I would also consider lapping the entire barrel. I lapped mine, 6 screwed the band, and thought it was gonna shoot great. Much to my dismay, it didn't change a bit until i tried moving the band around and changing how i was loading the barrel with the set screws. Now, about 1.5" forward of the original position, with the screws set right, its a tack driver.
Any magic formula for determining band position - or is it simply trial and error?
Steve
Definitely trial and error. I tried 2 bands, one in the original position and one at the end of the muzzle, and my shots were off with any pellet. I went back to one band about a 1/2" from the barrel sleeve and no issues since. So basically my barrel floats. That works for my setup. This past weekend I again tried a second band about an 1" away from the muzzle, and same issue with shots being off.
Joe
-
Great, thank you. Trial and error it is. May wait until the scuba tank comes from hydro... could be a lot of pumping otherwise! :P
Steve
-
Joe, you are definitely right. I moved my barrel bands and did 10 shot groups and it is amazing what a difference it makes. I probably did about 6 positions (60 shots) until I got it right. After all this the shimming is what finally got me where I needed to be.
-
Joe, you are definitely right. I moved my barrel bands and did 10 shot groups and it is amazing what a difference it makes. I probably did about 6 positions (60 shots) until I got it right. After all this the shimming is what finally got me where I needed to be.
Nice, glad to hear that you got it shooting right. How are your groups?
Joe
-
No more than 1/4" at 25 yards benchrested on a Caldwell bag. This is just plinking; if I do my part they are same ragged holes conistently for 22 shots.
-
No more than 1/4" at 25 yards benchrested on a Caldwell bag. This is just plinking; if I do my part they are same ragged holes conistently for 22 shots.
Sweet! That's what I want for mine... at the least the gun being capable, with me as the limiting factor.
Steve
-
Well, I must add that this also includes sorting my JSB 8.44 pellets using a skirt sizer, a great guy on these forums made for me, and using the yrrah roll method.
-
I've never sorted...maybe I might give it a go.
-
Thank you. Armed with this info and a baker triger, I now have a good trigger setup on my maximus.
Moving the pivot point on the link forward reduces the trigger pull when moving the sear, but increases the travel.... If you replace the coil spring behind the trigger with a lighter one, and make no other changes, you will immediately notice what feels like a 2-stage trigger, first as you compress the coil spring, and then as the link moves the sear which is loaded by the hairpin style spring.... If you install the upper back screw, as you screw it in, you will be tilting the trigger, moving the blade back at the bottom and shortening what you are perceiving as the 1st stage.... Eventually you will have no 1st stage, only the 2nd, harder stage as you begin to move the sear against the hairpin spring.... It is at this point in the movement that changing the pivot point changes the leverage, reducing the effort but increasing the distance the trigger will move during the second stage....
The lower back screw adjusts only the "over-travel" of the trigger (ie how far it moves after the gun fires).... and THAT is the one that can cause sear drag if set too close.... because it doesn't allow the sear to drop enough to completely clear the hammer.... causing erratic velocities.... DON'T SET IT TOO CLOSE OR YOU WILL HAVE PROBLEMS....
The third, front screw, if installed, requires drilling and tappng another hole in the space between the plastic lug and the front of the link lever, so that you can adjust the position of the front of the link lever.... Screwing it in moves the link up, pressing on the front of the sear, moving the back of the sear down and decreasing the engagement.... Taken to the extreme, it makes the gun unsafe as there is so little engagement that the gun will fire if bumped hard (or won't even cock).... If you redrill the link to move the pivot forward, the 2nd stage gets longer, and although the effort is less, you get a "creepy" trigger, which I find unsatisfactory.... You can compenstate by screwing in the third screw and reducing the sear engagement, but that will eventually make the gun unsafe....
So, what is redrilling the link accomplishing?.... It is reducing the 2nd stage pull (a good thing), but it is reducing the sear travel, causing more creep for a given (ie safe) engagement (a bad thing).... Is there a better way?.... IMO, yes, instead of redrilling the link, just reduce the angle between the legs of the hairpin spring about 5 degrees by bending it carefully.... Then you can have a safer sear engagement and yet reduce the weight of the trigger pull during the 2nd stage.... It doesn't take much to drastically change the trigger pull, try it and see.... Use a protractor, or simply draw lines on a piece of paper along the legs of the spring when stock, and then push the legs towards each other until the coils tighten up and the legs are at a slightly tighter angle when relaxed.... The tighter the angle, the less force required during the 2nd stage to move the sear.... Don't go too far, or you may make the trigger unsafe.... mind you it's an easy thing to bend the legs out again to change it....
The above assumes that you have replaced the coil spring behind the trigger blade with a lighter one, or you won't even feel the two stages.... I use a coil spring of the same diameter and length but made from 0.020" wire instead of the stock 0.028" wire, and find it just right.... If you want a really light 1st stage, you can go down to 0.016" wire.... Sometimes I don't even bother with the 3rd (front) screw, just replacing the coil spring, bending the hairpin spring, and installing and adjusting the two rear screws makes for quite a nice trigger, particularly for hunting.... For a target gun, adding the 3rd screw to reduce the sear engagement is nice....
Bob