"Tim Wescott" wrote in message
...
Ed Huntress wrote:
"Louis Ohland" wrote in message
...
On 3/14/2010 09:55, Snag wrote:
Wes wrote:
Louis wrote:

What are you making?
Andrew VK3BFA.
Small rifle action @ 22LR / 5mm / 22WMR / 22 K Hornet
What type of action?

Wes
Enquiring minds want to know !

It's a bit odd. A cylindrical falling block design from Bill Holmes.
Roughly 1" wide, 2" tall, 4" long. The falling block, er, shaft, is
.750" diameter.

Frank DeHaas ("Mr. Single Shot") designed one like that many years ago,
to be made with a lathe, for people who didn't have a shaper to carve out
the rectangle in a conventional falling-block action. Supposedly, it
worked very well. I still have a falling-block action for .22 Hornet, a
semi-replica of a Farquharson, that I'm saving to finish when I retire.
That may be after I'm dead. g

I was talking to my neighbor about it, and there may be some EDM and
heat treating shops in the ares. EDM would make a rectangular falling
block so much easier.

Caution. I have investigated this at considerable length. I also was once
pretty knowledgeable about EDMed surfaces, although I'm somewhat behind.
EDMed surfaces under shock and tension in a rifle action are not a
healthy mix. If you want to know more, we can discuss it.

Can you fix that with shot peening or other treatments?

No, not completely. The essential problem is that EDMing causes microcracks.
Peening just covers them up.

There's a lot more to it. The best equipment and the best techique can, for
all important purposes, get rid of microcracks. But the surface is still
remelted steel (the recast layer), and I would lap it off even using the
best EDM techique.

You may see photomicrographs of EDMed surfaces that show complete removal of
the recast layer, and no microcracks. But read carefully about how those
surfaces were accomplished. Generally they're the result of using the most
sophisticated techniques, in the hands of experts.

So the answer is, it can be done. But the typical toolmaker using typical
equipment may not do it, even if he thinks he is, because his molds and dies
never crack. The receiver of a falling-block rifle, which has to withstand
50,000 cup, is not a lunchbox mold.

I wouldn't shoot the gun, unless it has been proof tested multiple times. It
just isn't worth it. If you used good technique and left at least 0.002" for
mechanical finishing, it would be a different story. I've schemed up ways to
lap the surface but I've never tried it.

Before building a single-shot rifle, anyone should read deHaas's books. He's
the expert. His son has one or more books out, too. I haven't read them but
his dad knows his stuff, so they're probably good. DeHaas also is an
experienced critic of the common single-shot actions, and a designer of
several well-regarded ones himself. I'd stick to one of his designs or make
a straight replica of a Winchester Hi-Wall.

--
Ed Huntress