Anyone put a Lothar Walther barrel in .177 or .22 QB78?

[Gerard]

I've only had to smooth over that entry point at the rifling on one barrel, and old-stock Winchester .22lr barrel I picked up last year. It would scrape off shavings from bullets pushed through the bore. Not nice. So I wrapped some fine paper around a dowel with a short bit at the end tapered (in the drill, using a file) a little and pushed it in slightly as I spun it in the hand drill, working the roughly 1/4" long taper across that sharp edge for half a minute in each direction. Followed up with steel wool on the same dowel tip. I was careful not to push more than about 1/8" into the rifled portion and because of the taper didn't change that surface.

I don't see a problem with opening up the groove if you have a tougher O-ring to use, so long as it doesn't weaken the probe tip too much.

Here's a picture of the ring I put on my QB78D's probe. As you can see mine's red, not like the McMaster Carr stuff. Not that it matters. I got a 1" dowel of it a foot long a few years ago when thinking of trying to make a new seal for my Baikal 46m pistol. Unfortunately that didn't work out, too complicated for my skills at the time with this difficult material which tends to push before it cuts. Might try again some day. The slightly rough surface is typical of the finish I get with this material. Some day I hope to be able to turn it smooth, but dang it's difficult.

[imadunatic]

Gerard,

Took about 40 seconds in the lathe with a 1/8" die grinder and a felt bob to remove that burr. Thanks for the suggestion, funny how simple it can be sometimes yet we can't see it!

 Hope to have time at lunch to finish easing that leade transition. May even be able to test it out tonight if the weather cooperates!

Kevin

[imadunatic]

Well, ended up waiting until I had my full tune done (~12 FPE on CO2.... happy with that, especially on a .177) to put it back together and I can honestly say this story had a happy ending. I was able to hold ~1.5 MOA out to 60 yards with the JSB Exact Heavy.

What ended up being the ticket was washing out the last ~.500" of the barrel with ultra fine scotch brite until that tight spot was gone. Once I did that it started to hate the CPHP and CPUM pellets even more, but every other pellet tightened up at every range and the JSB Heavies started putting together tight groups at every range (.048" @ 10m, .148" @ 20m, .861" @ 40m and .796" @ 60m) and I am positive this gun and pellet combo is outshooting my optics and me and that is all I could ask for.



Thanks to everyone for the discussion and ideas. This rifle only needs a shrouded barrel and an SSG and I'm probably going to call it done for now. It may get a Delrin valve stem and regulated HPA this winter, but getting around 12 FPE on CO2 is pretty "dang" good and I'm not sure I want to toil. How much free time I have this winter will probably dictate that.

Kevin