Sunday, January 19, 2020

Project Updates: .25 Cal QB77

Still nipping away at the old QB77.  A year and a half ago, I converted it from .177 caliber to .25.  At the time, I made a quick carbon extension to hide the 12mm threading at the muzzle.  Didn't take time then to really refinish and blue the modified Benjamin .25 barrel where it fit into the breech.   That cold blue finish hasn't weathered particularly well and I'm now tired of trying to keep after it. 

Click on the pic and it will enlarge.   Here, I've loosened the barrel band and removed the carbon fiber barrel extension.  Follow the barrel back to the breech and you can see the discoloration and spot rusting.

Ordered a longer piece of 3K weave carbon fiber tubing (16mm OD/14mm ID) and waited patiently by the mailbox. 

Rough cut it to length with a hacksaw.  It'll run from the breech to the barrel band out by the muzzle threads.

Gingerly chucked it in the lathe and faced it to final length.

Razor sharp cutting tools are mandatory for working with carbon fiber, otherwise the material wants to splinter.

Some 400 grit paper put a good finish on the end.

Of course there was a snag--the carbon tube didn't quite fit over the barrel. 

Chopped a piece of delrin rod and cut a slit in the end for some emery cloth

120 grit worked well.  In about 20 minutes the tube was a snug fit over the barrel from muzzle to breech.

The barrel band will sit just aft of the muzzle thread.  The short piece covering the muzzle will butt against the band.  Should look like a continuous piece of carbon.

Backing up for a second.  This is what the QB77 looked like before all this madness started.  Pretty much a modern day version of the old Crosman 160/167.

This is where I'm at right now.

I've covered many of the modifications here on the blog.  The extended bulk fill gas tube, the AR2078 stock, adjustable recoil pad and barrel band...

At some point, I made a screw cup, fit an accessory rail, and made a knurled hand stop and cuff sling.

Took some time, but the QB has gone from a rifle I couldn't connect with to one of my favorites.   Not done yet.  There's some valve work on the horizon to find a bit more velocity for the .25 pellets. 

Thanks for checking in.