4140 vs. 4340 for pistol slide/frame

I have some questions on 4140 and 4340 regarding the suitability for use as material for a pistol slide/frame

1. How hard should the metal be to prevent peening of the breach face, locking lugs,firing pin retainer area,slide stop catch and muzzle lockup?

2. Will Melonite processing reach a temperature that would stress relieve the slide and frame?

3. Current idea is to rough machine the parts in an annealed state leaving enough material to do the final machining to avoid the inevitable movement/warp of the steel after quenching and tempering to desired final hardness.

4. Is 25-30rc hard enough for the frame and 35-40 for the slide? Looking to achieve durability and not become brittle, with the Melonite or DLC coating to handle the surface hardening for wear prevention.

We are looking at 416 and 17-4 as well for slide and frame for the stainless version.

I would use 4140 to whatever you what with 5 points between the two sliding parts to prevent galling.
Dunno about pistol frames but most bolt action receivers using 4140 are between 28 and 40 Rc.
4340 would have a small advantage in fatigue and toughness and IF you your parts were over 1" thick would be required for full depth hardness.


4140 doesn't become brittle, it only increases in yield strength the harder the tempered condition while decreasing in ductility.
So while it is possible to have the appearance of brittle failure it is only possible (assuming no heat treating cracks, sharp corners etc) when you have a load far, far beyond anything remotely reasonable and maybe with lots of slack to create an impact load.

17-4PH at H1025 ( RC 38) machines nicely and has no tendency to gall against 416 or 4140.
Melonite reaches 1075 deg F.

RWO

Doug W said:

I would use 4140 to whatever you what with 5 points between the two sliding parts to prevent galling.
Dunno about pistol frames but most bolt action receivers using 4140 are between 28 and 40 Rc.
4340 would have a small advantage in fatigue and toughness and IF you your parts were over 1" thick would be required for full depth hardness.


4140 doesn't become brittle, it only increases in yield strength the harder the tempered condition while decreasing in ductility.
So while it is possible to have the appearance of brittle failure it is only possible (assuming no heat treating cracks, sharp corners etc) when you have a load far, far beyond anything remotely reasonable and maybe with lots of slack to create an impact load.

Click to expand...

Thank you!

RWO said:

17-4PH at H1025 ( RC 38) machines nicely and has no tendency to gall against 416 or 4140.
Melonite reaches 1075 deg F.

RWO

Click to expand...

Thank you!