Source for 4340 bar stock?

Do you really need 4340? I think the major difference between 4340 and

4140 is hardenability. If you need maximum strength all the way thru a large section 4340 is indicated, if not, short pieces of 4140 flat will be easier find.

Looking to heat treat to Rockwell C 35, Tensile strength 160,000psi, yield 138,000psi, or there abouts.

You are exactly right on 4140 being easier to find...

It looks to me as though you might be able to get Rc35 all the way thru a 1" thick 4140 piece, but 4340 would certainly be more reliable.

BTW, I'm looking in "Modern steels and their properties," the best reference I've seen for this sort of data on alloy steels. Unfortunately I can't find an online copy.

I just go to my local steel stockholder (no help to you, in the UK)

AISI4340/EN24 is a standard product and should be available at least, in hot-rolled rectangle form. Only issue is that a steelyard will want you to buy a complete length. This is how you build up stock for future projects :-)

Mark Rand RTFM

What are you making? Andrew VK3BFA.

Small rifle action @ 22LR / 5mm / 22WMR / 22 K Hornet

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.

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.

What type of action?

Wes

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.

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.

I have at least three of DeHaas' books. My dad got wired up on this Bill Holmes design.

The significant question is how do you machine the passage for the block so it's got somewhat square corners? Or is a slight radius OK? I see the square broaches, but isn't an acutely square corner a good place for a crack to start?

One approach would be to drill four holes at the corners of the block passage, broach them square, then use a hole saw for gross metal removal, followed by a 1/2" mill to square up the sides. Is there a less manly-man way of doing it?

Before someone mentions casting, that is not an option.

For those up on DeHaas, look at the Chicopee RF. Problems: 3/16 CRS plates welded or silver soldered to barrel area. I like the swinging block, but I'm not sure it would do well with the 5mm. Look at the Chicopee CF action, and the bolt locking arrangement goes from a milled shaft (RF) to sort of a rolling block design (CF).

The drill the four corners, milling, some filing, and then figuring a way to lock the spindle of your vertical mill so you can mount a sharpened piece of HSS to use your mill as an ArmStrong vertical slotter comes to mind.

Wire EDM has issues. Ed Huntress has posted on this at various times. The jist of it is if they go slow, maybe not so bad but if they rip through it, you are likely going to have micro cracks. Now that I think of it, John, who runs a shop with big machines had some splines cut and the subject going too fast came up iirc in RCM.

I'm curious as in a question to the group, would the slotting device Bridgeport made to mount to the rear of the turret have the stroke to slot his receiver or more interesting to me, a Winchester/Browning 1885 High Wall receiver?

I'm still kicking myself for not getting to North Carolina with my uncle in time to pick up his free standing slotter he left in his basement when he divorced and moved away. Oh well his son got 1100 bucks for it on Ebay and the money financed his securities license. Son didn't think dad wanted it and after it turned out as it did, Dad felt good about his son getting benefit out of it. Sure would have been nice though to have it in my shop. Oh well, sometimes you win, sometimes you loose. Hard to feel bad on how that one turned out.

Wes

Wes

FWIW, my 1885 Browning (ne. Winchester Hi-Wall), which I no longer own, had radii of around 1/32" or maybe slightly more in the corners. My Farquharsen replica is about the same.

I don't have Frank's books anymore (I loaned them out and never got them back), but didn't he address that issue somewhere?

Bandsawing is one way it's done. There was a woman on the Outdoors Forum of CompuServe a couple of decades ago, an aerospace engineer, who made falling-block actions by drilling a start hole, bandawing the rectangle, and then finishing with a shaper. She made her actions out of 17-4 precipitation-hardening stainless.

Another guy I know bought my desktop shaper from me specifically for making single-shot actions. I'd start with wirecut EDM, leaving about 0.005" on each side, and finish with a shaper and lapping.

going to have

securities license.

my shop. Oh

========= From the more modern work [after most single shot actions were designed] on stress distribution, the corners contribute very little to the strength. Therefore it would appear that within reason a radius would be better as this avoids a stress riser [inside corner] as well as being easier to machine. see

?qid=29690

for pictures see

Sounds like a fun project. Let the group know what you decide.

Unka George (George McDuffee) .............................. The past is a foreign country; they do things differently there. L. P. Hartley (1895-1972), British author. The Go-Between, Prologue (1953).

Oh, the latest and best have. They've been able to produce a near-perfect surface for at least ten years. But it still takes some expertise with the particular material. And for a rifle receiver, I'd want to see a test coupon and photomicrographs.

Or plenty of proof loads run through it. Microcracks are insidious.

How about making everything slightly undersize and the applying Moglice or Turcite for the final fit-up. Should be a very slick action and if the Moglice is only a few thousandths thick the compression should be tolerable. Anyone know how Moglice/Turcite is for impact loads? If it works on ultrahigh speed million dollar machine tools, it should work on an small bore rifle action.

FYI

some hits for