QB-57 sighting in/consistency issue

[zartoon]

Greetings all,

I have a QB-57 in .177, and have been working on it, to make it into a shooter.
I disassembled it, and did a lube tune by doing the following:

- disassembled and used brake cleaner to clean out all the soy-based grease
- used sand paper to polish up the ends of the spring
- de-burred the pistol and cylinder using sand paper and barillo pad
- used automotive moly grease to lube the spring
- used a mixture of Beeman moly paste and pelgunoil to lube the synthetic seal
- assemble back up
- drilled the scope mount and the barrel wood stock all the way through and bolted using 6-32 counter sunk bolts with nylock/blue thread lock
- Leapers 4x32 scope with base, and drilled a hole in the scope mount for the lock pin on the rear scope ring.

I can zero it in, and it looks like its shooting 1/2" at 25 yards...then I get flyers...quite often.
I'm using RWS Diablo Basic pellets.

I have about 100 rounds through this..but it sometimes diesels.

can dieseling cause scattering of the pellets?

Any help or ideas would be greately appreciated.

-Z

[gamo2hammerli]

Well, it seems like you know what you're doing.  The only thing I would think you should've done is use Heavy Tar on the spring instead of Moly paste.  From my very limited knowledge Moly is to reduce friction between parts....and Heavy Tar is to dampen the vibrations (In the spring in this case)....which will probably extend the life of the spring too.  And you're right....dieseling will affect accuracy.  When the lubes burnt off abit.....maybe your gun will settle down.  Hopefully some tuners will chime in to help you out.

[zartoon]

I dont have any heavy Tar, and dont know what that stuff is.  
I guess at some point I need to buy some, but cant imagine moly-greaseing the spring is causing any issues..
I think the most it will do (not do) is get rid of the twang...

Any thoughts?

[daveshoot]

Are the fliers themselves in any kind of pattern? Tighten and loc-tite to the trigger guard stock screw?

Vertical patternsseem more likely to suggest velocity issues, which could be either the dieseling or the seals. right? If the seal was inconsistent, the velocity would be inconsistent, and therefore we'd expect elevation changes.

All-over sprinkles or horizontal, hmmm, we have a takedown barrel with a notoriously imprecise screw-down thingie. How's that holding up? If mine isn't reefed down hard,I can get rotation of the front halffairly easily. These things do not lock up very positively and there is a lot of playbetween the indexing pin and the keyway (my terminology for the alignment lock up thingies). Some herehave built those up to get a tighter fit. It would not take much rotation for POI to shift.

In the spirit of amateur guesswork, did youtry a crown inspection and polish? A small burr would gash outbound pellets with unpredictable results. Easy fix but I didn't see it mentioned, worth a shot if not.

[zartoon]

The fliers are all over...scatered.

I need to locktite and tighten the stock/trigger screws.
and I will examine the crown.  If its bad, I'll have to get a long brass screw and do the brass screw/polishing compound trick..and see if that works.
i'll probably end up taking the thing apart, and put it back together with heavy grease on the spring, and a mixture of silicone grease (dielectric grease) and pelgunoil on the seal. I'll then take care to not let much of he lube in the chamber to reduce detonation.

After that..i'm kinda at a loss...

[daveshoot]

Can you twist the barrel section much when it is "locked" down?

After all that, I guess the scope would be a suspect too. The 57sare pretty mellow shooters (especially after all your work) but they are still springers... if something was loose in the scope at the micro level, could that be it?

[zartoon]

once locked down, you cant move the barrel assembly.
Also, I've tried it with a Leapers 4x32 scope with the rings, as well as a leapers 3-9x40 scope with a lockdown base/rings (one piece) and its the same results..
I'm thinking itts either the power plant...or your bur theory on the crown is right...
I'll examine the crown today, and I'll take the action apart when my delrin spring guide gets to me next weekend....so hopefully that will tame her...
Am I missing anything else....?
I'm new to airgun tunning..but I cant imagine there is any voodoo to it......(or is there?)_

[longislandhunter]

I was just reading the other day that pellgun oil is in fact a petroleum based lubricant, something I didn't know.  If you used it, mixed with moly, to lube your piston seal I think you may be having a bad dieseling / detonation problem.   It would easily explain the randomly placed flyers you're getting.  I have 2 QB-57's,  .177 and .22 , and they are both extremely accurate with no accuracy problems at all.  Also, the crown on both of mine were fine.   Anyway, just thought I'd mention the pellgun oil fact.....

Jeff

[zartoon]

Jeff,

thank you for that.
What did you lube your seal with?
I can just use dielectric grease (silicone grease I thnk it is) which is supposed to be ok for O-rings.
I also have some RWS chamber oil that I can use...

what do you recommend/use yourself?

[longislandhunter]

If you're QB has the synthetic piston seal you can use the moly paste,,,, just don't mix it with the pellgun oil.  

You can also use the dielectric grease if you'd like, works fine.  Matter of fact I'm pretty sure that's what I used on mine....

Jeff

[zartoon]

Thank you Jeff,

I'm waiting for my Delrin spring guide next weekend, so once that gets in, I'll go ahead and take her apart again, and do the B3 spring change (the one from the QF-2 kit), put the new spring guide in, clean the seal (which is synthetic), put dielectric grease on the spring, automotive moly grease on the spring ends, and the moly paste on the synthetic seal.
I will also, at this point, blue locktite the stock screws.

One question I have is, should I shorten my spring guide, when putting in the B3 upgrade spring? or leave it stock length?

Thank you again,

-Z

[longislandhunter]

I  don't think there's any reason to shorten it.  If there is a benefit to shortening it that I don't know about I'm sure someone will chime in and let us both know      I did the QF-2 kit upgrade on my 3 B-3's and left  the spring guide length as it was,,, worked fine.  

Even though I don't really "need it"..... I'm thinking of ordering one of the "newer" style B-3's and tuning her up.  Something about the new stock and longer cocking handle just caught my eye and I keep going back and looking at the pics....

Jeff

[zartoon]

I'm' considering getting one of the B3-1s..and doing a tune on that....
so we'll see

[zartoon]

I'm still not able to get this thing to group at 25 yards..
the only thing I can think of, is that the wooden forearm stock that is supposed to be fixed to the barrel is not stable.
I tighten the two screws..but i'm not sure it is working.

My thought is to get rid of the wood in the equation and find a way to mount the scope, with some type of clamping bases that mount on the barrel itself..

Does anyone have any ideas or experiance with this type of mounting?

I was thinking of getting rid of the wooden forearm stock, maybe get two of these, with some 1" weaver/picatinny rings
http://www.pyramydair.com/s/a/UTG_Deluxe_Tri-Rail_Barrel_Mount/1785

and go that route...

Anyone have any better ideas..or suggestions for maybe a one piece barrel clamping type scope base/ring combo that would work and is affordable?

Any  help would be greately appreciated.

thanks,

-Z

[zartoon]

So I bought a pair of #4 Metric screws, these are the ones that index the barrel to the wooden forearm stock.
I chucked them up in my cheapie drill, and put the drill in my Bench Vise.  I ground the screws down till I had the pin the right size, and I replaced the screws this way. Now the barrel/wooden forearm are well fused.

So now, I'm thinking of two possible reasons for the scattered groups.

1. the piston assembly has a bent from the factory spring guide..and it pushes the spring into the "wall" of the piston.  
A replacement spring guide is on its way.

2. The pellets!!
I was using RWS diablo basics (7gr) and am now using crossman pointed field pellets (not premiers).
they both fit very loosely in the breech. maybe I need something that is a bit larger..and fits in the breech with more reistance...other than that..I'm running out of ideas fast...

what do you guys think?