How hard is OTC 4140 Chrome Moly

[epanzella]

Here is my situation. I'm getting ready to bore and thread a 4140 McGowen barrel blank for a breech plug. The hole is a bit complicated with multiple ID's and shoulders. A portion is also internally threaded. The OD has some threading as well. This will be a smokeless muzzle loader. As the tolerances in this hole are critical to avoid gas cutting, I would like to have a dress rehersal before opening night. This would require buying a piece of 4140 over the counter to practice on. (I have no extra barrel to sacrifice) Since 4140 can be heat treated I wonder what state a 4140 gun barrel blank is in when purchased vs an unpurposed piece of 4140 from a supplier. I have inqueries to both the barrel maker and my supplier but no response so far. Thanks.

 

[Stob]

You won't have any problem turning and threading a barrel blank. Whether stainless or chrome moly, they aren't that hard.

The only exception I've seen was a Lothar Walther barrel. I won't work on them.

 

[Defens]

How about just contacting the barrel maker and seeing if they could send you a couple scrap barrel ends? They must have a few odds and ends kicking around - 6-8" long.

 

[epanzella]

How about just contacting the barrel maker and seeing if they could send you a couple scrap barrel ends? They must have a few odds and ends kicking around - 6-8" long.

Good idea and worth a try.
Thanks,

 

[dave2176]

Tensile strength is about 70,000 psi. Brinell hardness 200. Should machine well.
Dave

 

[dulltool17]

You won't have any problem turning and threading a barrel blank. Whether stainless or chrome moly, they aren't that hard.

The only exception I've seen was a Lothar Walther barrel. I won't work on them.

Say what? Lothar Walther barrels are no harder than any other barrel. 4140 is 4140. HSS works just fine.

Obviously, you've had a different experience, but I didn't think they were terribly hard.

 

[epanzella]

THANKS, GUYS.

 

[Stob]

Say what? Lothar Walther barrels are no harder than any other barrel. 4140 is 4140. HSS works just fine.

Obviously, you've had a different experience, but I didn't think they were terribly hard.

In hardness, they may be no harder than any other barrel. But the steel is gummy. I haven't look at their website in a very long time, but they used to have their own "brew" of cutting oil to use because of the steel. It was equal parts of Rigid Cutting Oil, TapMagic and MolyDee.

It still didn't make things easier. I have done a few since the first, but I won't use any of my own reamers in one. A customers reamer, fine.

Edit:
Dulltool1, I did not realize you were refering to the CM barrels from LW. I have never chambered one of their CM. By far, the majority of barrels I work on are match grade stainless steel. LWs "stainless" is what tey call R700 not 416R.

 

[Rick Leslie]

I've done a few 'smokeless' muzzle loaders for friends as well as one that uses cut down .45 Colt brass for ignition. Most barrels are relatively soft, 28 to 32 Rockwell C I believe. For practice you can use most any carbon steel. Most mild steel turns the same or close to 4130 and 4140. I've always used HSS for threading barrel as well. (I've done enough of those that I quit counting about 25 years ago.) If you want barrel stubs to practice on, check ebay for gunsmith drops. I saw an auction for about 30 lbs. of drops for $10.00 plus shipping.

Good luck and have fun.

 

[dulltool17]

Stob- I've heard that about their SS barrels as well. Different materials; different experience.

Good for you with the SS barrels- I don't think I've got the patience or skills to deal with them

DW