Hand working steel for rifle action

Greener Jim · Dec 7, 2017

New member here, hoping you guys can help.
So I’ve had a little bit of a baby over the last year or so, I’ve designed a rifle action in my off watches at sea.
The receiver ring will be machined and the bolt head is a Savage item. However there is a few bits which aren’t pressure bearing, but must be tough, which I wish to make by hand (files and a small amount of pillar drill)
What steel could I use for this? I would of course be using whatever steel it is in the annealed state. 4140 is easy to get and will be what the receiver ring is made from but I’ve never tried hand working it.

Thanks in advance,
Jim

Anthony · Dec 7, 2017

Will the parts that need to be tough be toughened or heattreated? If yes, medium carbon steel. If no, low carbon steel.

In any case you will absolutely need a good file card.

MIBill · Dec 7, 2017

Greener Jim said:
New member here, hoping you guys can help.
So I’ve had a little bit of a baby over the last year or so, I’ve designed a rifle action in my off watches at sea.
The receiver ring will be machined and the bolt head is a Savage item. However there is a few bits which aren’t pressure bearing, but must be tough, which I wish to make by hand (files and a small amount of pillar drill)
What steel could I use for this? I would of course be using whatever steel it is in the annealed state. 4140 is easy to get and will be what the receiver ring is made from but I’ve never tried hand working it.

Thanks in advance,
Jim

Jim,

I would not even waste my time with 4140 annealed... Get pre-hardened ("4140PH") It is VERY easy to work with standard hand tools through the 30's Rhc. It is easy to find pre-hardened 4140 in a variety of hardness ranges from about 28 - 31Rhc through 35 - 38Rhc. It cuts well with a file and IMHO is easier to drill and mill than annealed.

Pre-hardened dosen't necessarily mean hard to work with.

Greener Jim · Dec 8, 2017

Well that does make things easier Bill. I love in England so it’ll be EN19T but it’s the same stuff. I can get it easily and cheaply in the T condition you see so using that does make it easier.
Makes it easier for final heat treat also.
Will I need any special bits for the pillar drill?

MIBill · Dec 8, 2017

Greener Jim said:
Well that does make things easier Bill. I love in England so it’ll be EN19T but it’s the same stuff.

That is my understanding as well.

Greener Jim said:
I can get it easily and cheaply in the T condition you see so using that does make it easier.
Makes it easier for final heat treat also.

The point of using a steel that has already been heat treated is that there is no need for a final "heat treat". This eliminates the concerns of warping during heat treatment. Shape the part and go. It is how most of the firearms industry does it, at least in this part of the world.

Greener Jim said:
Will I need any special bits for the pillar drill?

The short answer is, as long as you stay in the Rhc 38 and lower range any GOOD HSS drill bit will work just fine. Where problems start to occur is in the low to mid 40's Rhc. With that said I typically use HSS tooling on the lathe with 4140HT but use cobalt tooling on the mill (including 135° split point drill bits). If surface finish is important I would drill slightly under finished size and ream to final size.

Greener Jim · Dec 8, 2017

The reason I was planning on final heat treat is because 4140T/EN19T is, as you stated, 28-31Rhc but most custom actions seem to run 38-40Rhc.
If I’m good to go with out the box EN19T then that does make my life easier.
The main reason I’m trying to work all this out is so I can do the calculations so I can add final dimensions to the design. I can’t do that without the metal.
At work they just give me specs and I go from there, never had to spec the material myself!

billzweig · Dec 8, 2017

I am not a gunsmith, though I did a fair number of custom work - mostly on bolt action rifles - and did make a few actions as well. In most cases I prefer to use mild steel and to deep case harden it after machining. For springs or parts that flex I use A2 or D2 steel heat treated to the necessary temper on the finished part.

MIBill · Dec 8, 2017

You SHOULD be able to find 4140HT pre-hardened to Rhc 34-36 without to much trouble. Actually MOST firearms parts made from 4140 would run somewhere in the 28 - 38Rhc neighborhood. I think it would be rare to go above 38Rhc. I built a prototype action in .50 BMG (The finished action is on hold pending the move of my shop in the spring/summer) out of 4140HT and the hardest piece was 35Rhc. There is no compelling reason to much if any harder than that for firearms parts made from 4140. Of course there are parts that are best made from much harder materials like some components in the lock ("trigger") mechanism. But for the action, bolt head and cosmetic pieces, I don't see the point.

You never said WHAT exactly you were looking to make from this steel...

MIBill · Dec 8, 2017

billzweig said:
I am not a gunsmith, though I did a fair number of custom work - mostly on bolt action rifles - and did make a few actions as well. In most cases I prefer to use mild steel and to deep case harden it after machining. For springs or parts that flex I use A2 or D2 steel heat treated to the necessary temper on the finished part.

For cosmetic parts, case harden mild steel will work well enough. I never went that route since until recently I was a blued steel kind of guy. It can sometimes be a major pain to match the bluing on a receiver with blued mild steel... I just have stuck with making anything on the outside from 4140 out of habit.

Greener Jim · Dec 8, 2017

Unfortunately in the UK 4140 is very rare, EN19 is easy to get as stated but everything I’ve looked at is 28-30Rhc. We simply don’t have the same variety as you guys.
I ran some numbers and I think it’ll be ok but I’ll enquirenwith my steel guy and see if anything a little harder is possible.

As for the rifle, it’s my own design but similar principle to a Cogswell and Harrison Certus (bolt handle at the front of the bolt) but built much tougher. Will feed from Accurate Mag bottom metal. The case is 338 Lapua necked up to .458”, I call it the 45-120 Rimless but it’s similar to a 450 Rigby really.

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