QB5-10 up grade to .22 cal. has anyone else tried this?

[JJ]

     I finally made time the other morning to take a crack at resealing my QB5-10. I was surprised at how simple that gun is, I don't know what I was afraid of.... I managed to make a temp. seal repair, until I find the right material to make a proper one. After I got it holding air and shooting (harder than it did when I got it!), I started to wonder what kind of mods. I could come up with. The fist thing I came up with, besides new Furniture, was .22 cal.. I looked around and found a few old barrels but the QB-78 (standard) Barrel had an incredibly close O.D. This is a good start...
 The List:
-Cut and polish barrel breach to fit receiver. Done
- Drill and tap new set screw for barrels ( old barrel was JB welded in place when I got it).
-barrel bands need a little reaming.Done
-drill out pellet shuttle, to fit .22 round ball only. For regular pellets, I will need to make a new "shuttle", and                   machine "shuttle track" still pondering this, I will see how the round balls shoot
-open up pellet feed tube and gate, with dermal.
-Remove ugly finger groves from pistol grip. Done
-new pump handle and pistol grip scales.
-scope mount.
- and last but not least, a Shroud, this will be easier with the longer barrel. 
- I will wait to see how it functions before I start to mod the valve...

     I managed to get the barrel in place to make a few (manually loaded) test shots. I think the additional barrel length is helping to make up for the drop in velocity when switching to a larger caliber. I don't have Chrony, but the "pine board test" is putting it pretty close to my .22 cal QB-78, with 8 pumps. I think this is going to work out well.
I plan on posting pictures and updates as the progress continues.
  If any body else has done this, I would love to hear what they came up with..
Thanks for reading!

[pantherpatrick]

That is really cool what you are doing

[Jaymo]

I need to dig mine out and reseal it. I thought about modding it to take a QB78 valve stem.  The original valve seal blew out pretty quickly.
I want to file down the finger grooves and Duracoat the pistol grip. Also want to make some thicker pistol grip slabs.
Maybe mahogany, maybe Micarta.

[JJ]

   I never thought about Micarta, That would be nice!
  There is a way to drop in a modified valve stem from crosman 13XX, with out modifying the valve it self. All you need to do is cut down the valve stem and add a O-ring or seal of some kind.. I have not tried this yet, but I know the stem fits nicely. I looked at the QB78 valve, but I thought the crosman needed less work.
   I am currently trying to find Roundball ammo in .22 cal or "F" lead shot. Seams like everyone is sold out lately..

[JJ]

  So I found some .22 cal. or "#F" lead shot on line last week, However I wasn't thinking that the bore of my replacement barrel for the QB5, would be a little tighter than .22".  They fed well threw the magazine, but they would jam in the breach of the old .22 cal QB78 donor barrel (narrower standard QB barrel).
   I am looking at ordering "#TT" lead tomorrow witch is .210", but there is also a Nickel plated Lead #F that is .215" = 5.6mm. Hmmm.. cant really get samples, so I will need to commit to 8lbs of one or the other.
  With the changes I have made so far, I think this is going to be a handy gun in the end. I like the way the round ball ammo shoots, It hits hard! 
    Oddly enough the Lead #F shoots really well in my QB78 witch the heavier 15mm barrel. There is a small amount of resistance at the end of the bolts travel, but when you pull the trigger that ball screams down range.

  I have read that the chinese don't change there tooling that much so the ID can change from barrel to barrel on the same model of gun.. Maybe that is what is happening here.