Disco Sear drag...actually barrel bands

[ivanpros]

Anyone have information on how to get rid of sear drag on my disco? Is there any pictures on "how to" mods?

I have the brass trigger replacement, but I do not want to have to modify the stock with the marauder trigger.

Just want a decent trigger that I can either modify or purchase and drop in. My Disco is great with the exception of the sear, every time I squeeze slowly vs. fast.

Thanks.

[madmullet]

Have you polished all the internal sear surfaces and the hammer.  I just added the B&A trigger to my 2260 and gave it a good polish with 1000 grit sand paper and some flitz until they have a mirror finish on them.  It will defiantly help allot.  I know that Air guns of Arizona sells a adjustable sear that will work but they have a crappy E-Comerce site and I refuse to use it. 

[rsterne]

If you're getting sear drag, you likely have the overtravel adjustment adjusted too tight.... I've used a zillion 2260 / Disco triggers, and properly adjusted there is no problem....

Bob

[ivanpros]

If you're getting sear drag, you likely have the overtravel adjustment adjusted too tight.... I've used a zillion 2260 / Disco triggers, and properly adjusted there is no problem....

Bob

It was adjusted by by Tim at Mac1 so there is no overtravel; he adjusted for it. Also checked and there is no sear drag marks that I can tell on the hammer.

Well, I am looking at option 1, take it back to Tim to look at it or option 2 buy a new trigger mechanism from Crosman and try it on.

Here are 5 (3 shot groups) at 1.9K fill and 5 (3 shot groups) at 2.1k fill

Chrono check
1. 816
2. 817
3. 814
4. 809
5. 812
6. 815
7. 809
8. 814
9. 810
10. 809
11. 808
12.807
13.806
14. 799
15. 798

[rsterne]

Tim knows what he is doing.... but no overtravel is likely to cause problems with sear drag, in my experience....

Bob

[nervoustrigger]

Ivan, I second what Bob is saying.  Firstly that Tim knows what he's doing...everyone here knows that.  Secondly that some amount of overtravel is needed.  It's possible that, in a precision assembly with polished low-friction surfaces, that the overtravel may be hard to detect.  But it has to be there.

That last group of 15 shots...I don't see any velocity abberations indicative of sear drag.  Did you adjust it to allow more overtravel for that string?

[ivanpros]

Thanks for taking the time to work with me on this. This is my first PCP and I am somewhat over my head since switching from springer/nitro  rifles.

Yes, I adjusted for overtravel prior to both strings; based on Bob's advice. I was getting same hole groups for a while at 20 yards, but now it starts high after every fill and gradually moves to low; these were at 25 yards.

[nervoustrigger]

Your extreme spread in that last string was only 2.3% which is really good, and it started at a peak so you can probably fill to a higher pressure and get a longer shot string.  Perhaps more than twice as many shots.  It's not unrealistic to think you could get as many of 35 or 40 shots inside of 3% ES which would be really nice.

[ivanpros]

I was feeling down and out this week with not being able to figure this out, but I did some research on the forums and the light bulb went on again.

I noticed my vertical shift for POI changed when I added the 2nd barrel band. I thought it would be a easy fix by adding it and securing the barrel, but looks like it might take some tinkering to figure out the best adjustment. I will make some adjustments this weekend and see what happens.

Anyone have advice on best approach to test the barrel bands? I also saw mentioned to use tape in between; not sure how this work.

[ivanpros]

Happy to say I found it right here in GTA search and great feeback from you guys. I started with one barrel band standard ( where it normally sets) and added the second barrel band right before the end of the barrel. I was getting groups that looked like a stack of pelllet mud, on paper at 25 yards.

I went ahead and experimented and the best setting was one barrel band standard (where it normally sets) and one right behind it; almost touching the wood stock.

Lastly I noticed that 1.8k fill was the best fill so it does not expand and change my POI.

I am considering ordering the barrel bands with the extra screws. Is this something I can do at home with a drill or is it best to just order it from TKO?

Thanks.

Great Topics:
http://www.gatewaytoairguns.org/GTA/index.php?topic=23676.msg214238#msg214238

http://www.gatewaytoairguns.org/GTA/index.php?topic=43070.20

[C.ALLS]

Happy to say I found it right here in GTA search and great feeback from you guys. I started with one barrel band standard ( where it normally sets) and added the second barrel band right before the end of the barrel. I was getting groups that looked like a stack of pelllet mud, on paper at 25 yards.

I went ahead and experimented and the best setting was one barrel band standard (where it normally sets) and one right behind it; almost touching the wood stock.

Lastly I noticed that 1.8k fill was the best fill so it does not expand and change my POI.

I am considering ordering the barrel bands with the extra screws. Is this something I can do at home with a drill or is it best to just order it from TKO?

Thanks.

Great Topics:
http://www.gatewaytoairguns.org/GTA/index.php?topic=23676.msg214238#msg214238

http://www.gatewaytoairguns.org/GTA/index.php?topic=43070.20

I just finished doing the additional set screws in my barrel bands. If you're going to try it at home you'll need a drill press IMO.

[Ribbonstone]

Long-long ramble about Crosman barrel bands.



Going to add to your confusion: haven’t found one way that always works.  Am thinking that there are several ways to deal with barrel bands and stability, and so long as your results are good, doesn’t much matter how you got there.

 LOOK FOR OTHER PROLEMS FIRST:

#1.  Take a good hard look at how the breech fits to the air tube.  Some of them seem to have a transfer port that’s a little high, so the breech never really has a chance to be pulled down into full contact with the bottom tube. 

#2.  Some barrels are crooked/bent.  Hard to get the system working right if your barrel is bent up, down, or to one side or the other.  Understand, a curved barrel can still shoot well, but it plays *(&^ with the barrel band system. 

So if you find that you have to “spring” the barrel into alignment in order to slide on a barrel band, chances are you have one of the above two problems (or both).


LOTS OF ROADS TO THE SAME PLACE:

Doesn’t seem to be one universal cure, everyone seems to have a favored way, but there are several paths and each one can work.  Guess it’s the rifle that has the final say so, and some folks are lucky enough to have a Discovery that needs only a little bit of work to get stable and others have a bigger job to get it there.

Lot of Disco owners just add a 2nd band.  Can use a Disco band or one for a 2240/2260 (although as you can see, the polish level is different). This was my first Discovery, and adding that 2nd band was all it needed to act right.




WHAT DOES A BARREL BAND REALLY DO?

Lot of match guns and high accuracy sporting PCPs have bands, but mostly they are set up DIFFERENTLY than the Discovery.  Match/high end sporter PCPs with bands generally have the bands inletted/anchored to the stock and allow BOTH the air tube and the barrel to slide freely in and out. Those bands are aligning the barrel and tube, but not restraining either.

You can’t have that with a Disco (without a good bit of modding).  Discovery air tube is going to expand/contract/lengthen as pressure changes, and it’s better if those changes aren’t transmitted to the barrel. So I’d want “tight to the tube” to avoid point of impact shifts from band rotation, but not tight to the barrel (no slack, but not tight).

IF you want to try adding two more screws (for a 4-screw band) or adding 4 more screws (for a 6 screw band),  then add them at an angle going though the thick middle section of the band where the screw can gain a long length of threads.

4-screw band:






6-screw band is the same as above, but with two more screws angled “up” to tripod the barrel.




((((((  I’D PASS ON THE 6-SCREW BAND.  Easier to do the 4 screw mod, polish the inside of the band where the barrel rides, wrap the barrel with Teflon tape until it’s a slide fit. ))))))



Adding a barrel band just ahead of the breech works well to fix the breech more solidly, which has done good things for keeping the point of impact stable. That horrible little breech screw isn’t so crucial with this set up (in fact, can remove it and not really notice a difference).







Challenger PCP uses a rear barrel band  like above, and a front one.  Front one is special, it’s much too large to capture the barrel and doesn’t have an upper set screw. Front band’s job is a “bumper guard”, in this case with a good bit of space.



Challenger front band probably has way more "slack" than really needed:



So I ended up setting my Discovery up pretty much like a Challenger  tight rear barrel band at the breech to pull that breech down hard and stabilize the rear end of the system, and a barrel band at the front that fits tight to the tube but allows the barrel to slide in and out.

[ivanpros]

Thanks, I did look at the barrel and is straight. Also looked at how the barrel sits in the breach and it is slightly tilted upward; barely noticeable. The barrel bands fit loosely, but I did tighten the air tube first and only slightly tightened the barrel. I guess I will try the quick and dirty fix with 1/2 in. aluminum can shims.

My Disco is now worthy of JSB down the barrel.