On Tue, 13 Sep 2005 17:48:03 +0100, Peter Wiley
wrote:
In article , DoN. Nichols
wrote:
According to R. O'Brian :
The standard rim thickness for the 22 rf is .044" Therefore the headspace
in a revolver needs to be .044" + enough to allow free rotation of the
cylinder. I don't have the industry standard dimensions to hand, but
.048"-.050" should be plenty. A real headspace gauge looks like a short
cartridge case with the proper thickness rim machined on it. They are
commonly made in Go and NoGo sizes. In practice you can use a cartridge and
a feeler gauge since the actual dimension is not too critical in a revolver.
BTW, the ratchet teeth do not determine indexing. It is controlled by the
cylinder bolt in the bottom of the frame window locking into the bolt
notches on the cylinder OD. Thus, the indexing accuracy is determined by
the accuracy of the cylinder machining when it was made.
But the ratchet teeth need to move the cylinder to the proper
point so the "cylinder bolt" will drop into it. If the notch is not in
line, then the hammer will fall with the cylinder out of line. If it is
a *lot* out of line, the firing pin won't hit the primer, so there will
be no real problem (assuming that your life is not depending on the
thing firing when the trigger is pulled), but if it is just slightly out
of line, then the cartridge will fire, and it will (at best) spit a lot
of lead out one side or the other. With something as small as a .22,
and with as large a sensitive primer area (the whole rim), I could see
it being out of time by 1/2 the diameter of the bullet, which could be
quite nasty.
So -- make sure that when you are done, the locking lug
("cylinder bolt" above) falls cleanly into the index notch -- *before*
you ever put any ammunition in it.
Check what happens both with slow cocking and fast (as with
fast, it is likely that the momentum of the cylinder will spin it a bit
more, so the locking lug will drop in anyway as the notch tries to spin
past it).
And -- if it is double action -- see whether the behavior is the
same when it is driven by the trigger instead of the hammer (as wear in
the linkage between them could cause shifts in the timing, depending on
just how the indexing pawl is driven. Those that I have seen were
directly driven by the hammer, but a worn or sloppy bearing pin for the
hammer to rotate on could shift in different directions, depending on
whether the hammer is being pulled back by a thumb, or cammed back by a
trigger.)
So -- make sure that you know what it is going to do
mechanically *before* you let it fire live ammo.
Agree with all of the above. It can be a right fiddly PITA to do, too.
However, if you're only making one cylinder, or a couple, for the same
frame, here's what I did.
First, I cut the indexing star and made sure I had that right. Second,
I cut the locking bolt recesses and checked the cylinder locked up
tight. At this point I had a solid cylinder with indexing star and
locking bolts. I'd sorted end shake, headspace etc etc as well.
Then I made an accurate threaded barrel stub with reamed slip fit hole
on centre. Custom made centre punch to fit the bore. Remove barrel,
substitute barrel stub, bring cylinder to lockup, then use the punch to
mark the cylinder face. Ditto for all chambers. Worth doing it a couple
of times, not being too heavy handed, to check repeatability.
Now you *know* the centre of each chamber, at the important end - where
it lines up with the barrel. Pick up the centres, drill/bore/ream each
chamber. For a 22, using 4140, call it done.
Worked for me.
PDW
Greetings Peter and DoN,
I have decided to nix the extra cylinder. I feel that the smaller
pistol is too light weight for .22 mag and the other, top break pistol
may be too weak at the top for .22 mag. However, the smaller pistol
does need some work done on the cylinder system. As DoN suggested, the
indexing may be different faster or slower, trigger vs hammer. And
this is true. When using the trigger or hammer slowly it will index
perfectly. However, using the trigger fast will sometimes cause the
cylinder to index incorrectly. When this happens the trigger jams, as
does the cylinder. Fortunately, the hammer locks in a safety position
before the cylinder jams. So the hammer can't fall on the round. It
doesn't always jam. Just maybe one out of 40 or 50 trigger pulls. So
it's obvious that work needs to be done to this pistol. So, the first
thing to do is get the cylinder back in shape as mentioned in a
previous post. Then the indexing will be addressed. It looks like I'm
gonna be real familiar with this pistol when it's finished. Thanks for
the good advice.
Cheers,
Eric
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