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Discussion Starter · #1 ·
Hello all, I was looking into getting a nitride salt bath treatment (like melonite qpq) for some parts my 582 mini. Ive seen people in other boards get it done on m14s with excellent results but I don't know if anyone has ever done it on a mini. Are they too different for comparison?
 

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Discussion Starter · #3 ·
The process is used on the barrels of some rifles like the bushmaster acr and sig556 in place of chrome lining. It increases wear and corrosion resistance. A similar process is also used on glock slides. I was originally planning to just get the barrel done but the blue finish comes off so easily I started thinking about getting the op rod and receiver done too.
 

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Nitriding offers a wide range of excellent properties achieved at lower temperatures than hardening with less distortion (500 degrees C). I see no problem with Nitriding all the steel parts of your rifle (except springs), if done to sufficient depth.

If the receiver and bolt are nitrided only to 0.002" as is common for barrels the core hardness could come down a little from the original tempering, without putting back the strength in the outer layer. 0.002" is OK for the barrel as that is not very hard anyway, but the bolt and receiver locking lug area I would want nitrided to 0.02".

I would only have nitriding done after the rifle has been used enough to prove reliable - if any cutting or polishing is required after it will be very difficult and would reduce the hard layer thickness.

Nitrided alloy steel has a hardness of 70 Rockwell C - harder than a file. It is also very slippery but does not smooth out roughness that was there before nitriding. It is better than hard chrome for corrosion resistance.

You may find that the cost of nitriding helps you make this decision... I would be very careful in choosing the company to do it and only use one that knows firearms and treats them on a regular basis.
 

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Pulled from a post on 1911 forum:

The tempering temperature for 4140 steel to reach the typical 1911 slide's 40 Rockwell C is almost 800 degrees F. The frame is softer and can stand even higher temperature before softening further.

See tempering temperature vs hardness chart taken from here: Heat Treating 4140 steel FAQ : anvilfire.com How-to.

SAE 4140 Steel Tempering

Tempering Temperature; Hardness Brinell; Hardness Rockwell; Tensile Strength

400°F 200°C 514 HB 55 HRc 297 KSI
500°F 260°C 477 HB 50 HRc 243 KSI
550°F 290°C 461 HB 48 HRc 235 KSI
600°F 320°C 444 HB 47 HRc 225 KSI
650°F 340°C 429 HB 46 HRc 217 KSI
700°F 370°C 415 HB 44 HRc 210 KSI
800°F 430°C 363 HB 39 HRc 182 KSI
900°F 480°C 331 HB 36 HRc 166 KSI
1000°F 540°C 293 HB 31 HRc 145 KSI
 
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