Rich - I got the .22 barrel....

[vinceb]

and MAN did the job give me heartburn! This is a very late-model Shadow, BTW.

I warmed up the breach block just like you said, and it did NOT want to come loose. Only when I clamped the barrel directly into the vise did it finally cooperate - sort of.

As turned the breach block, I could hear and feel metal being ground and torn up. As the barrel started coming out, I could see that the threads on the old barrel were completely destroyed. I frequently had to stop, give it a turn in the other direction, and then continue unscrewing it.

Finally it came apart, and I could see that the first 1/4" of the 14x1.0 threads in the block were mangled. I took my dremel-type grinder and just ground that first 1/4" away until the threads were gone... and the new barrel would not go in.

It turns out that the front of the block was constricted - the ID was about .4mm smaller than the OD of the new barrel threads. A fair bit of work with the grinder took care of that, and using a small 7x1.0mm tap as kind of a rotary file, I was able to debur the entrance to the remaining threads. I finally got it so that the new barrel screwed on easily... much to my relief!

Fortunately, I didn't really lose anything with the missing threads - since the barrel threads do not go all the way to the base of the finished part of the barrel anyway I didn't need all those threads in the block. In fact, by my measurements I only lost about 2 threads worth of engagement.

Near as I can tell, the original barrel was screwed in so tightly that it actually smashed down the forward part of the breach block and mashing the threads together. There is actually some mushrooming on the original barrel where it met the block.

Obviously, my .177 barrel is ruined... but at least I've got the .22 barrel successfully installed.

So whaddya think happened? A fluke, or is Gamo trying to make sure that we don't go swapping barrels like this?

If it starts to turn and you hear that noise you can spray with WD40 and it will free it up. I had one do the same thing on me now I have a can of WD 40 handy.

 How bad is the .177 barrel messed up? I can machine down the O.D. to a little smaller size and fix it. I screwed one up  but only on the muzzle end so I just shortened it to 15 1/2 inches and screwed it into my old shadow .22 and it shoots great.

[vinceb]

BTW - I neglected to say "Thanks!" for getting it out as quickly as you did. I really appreciate it!

In any case, I don't think some WD40 would've let it come out much easier. Like I said, the front 1/4" of the breach block was too narrow to accomodate the new barrel, even after I ground out those threads. I really had to hog it out. Once I got past that first 1/4", it was fine.

Here's a shot of the old barrel:

[vinceb]

...and open-sight accuracy certainly seemed good enough, especially since I was using mostly Gamo Hunter pellets (not the best in the world).

Velocity was a bit low (660-680 with Gamo Match), and the gun had some barrel droop that I didn't notice before.

After shooting, I decided to see about the droop - and discovered that the breach end of the barrel stood proud of the breach block face... to the extent that it was hitting the mating receiver face and preventing full breach closure. Of course, it looked like the breach seal was not able to seal properly.

I filed it down level with the block face, and no more droop! Since the breach now seems to be sealing the way it should, I suspect the velocity will improve.

Tomorrow will tell...

I have measured a bunch of barrel pivot blocks of shadows and hunters and the difference in them was from .003 to .006. It might have been from the original barrel being screwed in so hard it crushed to pivot block a bit.

680 is not that bad for those pellets, at 14.2 grs.

Gamo says 750 fps but I have never heard of one that will do much over 700.

[vinceb]

A few weeks ago I tried putting my .22 cal B19 barrel on my very healthy Quest (doing 930 with CPL's), and got a few shots to hit 750 (most were around 740) with the same pellet. That's why I was a wee bit disappointed - but, like I said - I suspect that the velocity will come up a bit now.

I suspect that you are right about the barrel/block mismatch. As you can imagine (from the picture of the old barrel), the forward face of the breach block was gouged pretty badly. I'm sure that's got something to do with it. If Gamo actually sole PARTS, I would have liked to have gotten a whole new block.