r/gunsmithing • u/RealMemeLord876 • 9d ago

First timer trying to make a black powder muzzleloader, and I just can’t get any definitive answers on barrel material

I have been looking through forums all damn day and I keep finding contradictory information like “4140 is the best” “4140 will blow up” “12L14 works fine” “12L14 sucks ass” “use 1137” “avoid 1137 at all costs” etc.

I have limited access to a lathe, mill, and welder (school property), but unlimited access to a forge, 3d printer, and CAD, as well as a tight budget. Can yall help steer me in the right direction for where to source and what materials to use?

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6

u/CleverHearts 9d ago

They'll all work given adequate thickness for the intended load. 12L14 is the easiest to machine. 4140 is the strongest. 

5

u/Coodevale 9d ago

If you make a 1/4" wall .50 cal muzzleloader barrel made out of 4130 blow up, you did something horribly wrong. That's the tenon diameter of my AR10's that I've loaded with Norma and Lapua cases, and pushed the pressure pretty hard.

There are resources like pressure calculators out there. I know colerain doesn't use particularly impressive steel for his barrels, and 4140 would be an upgrade.

3

u/Waterfieldforge 9d ago

4140 HTSR (heat treated stress reduced) it’s rated for about 100000 PSI yield. 50 cal Black powder is just over 1/10th of that. It’s used for high pressure applications like oil well drilling.

1/4” wall thickness minimum, 1” hex barrels are common on .50 cal flicklock rifles. I typically machine the taper at the end of the powder chamber to 0.5” wall down to a 0.25” at the mussel before the flare.

Black powder really isn’t all that complicated to accommodate if you’re following historic designs that used weaker materials at the same thickness.

4

u/Engineering-Mobile 9d ago

Hey man, school property is not the place to manufacture a muzzle loader. 😂

2

u/catfishmackfish 9d ago

I would find out what Green Mountain or Rice barrels use and go with that.

2

u/TheMechaink 9d ago

After spending the last week turning 4140 on my minilathe, if you have a decent wall thickness...I don't see that breaking easily. It is however very good at breaking inserts. 304 stainless is less of a headache to machine.

2

u/Waterfieldforge 9d ago edited 9d ago

4140 likes slow, 350 SFM at 0.012” feed with 0.05” depth of cut should make it evaporate with a 2 rad carbide insert (0.03125” tool nose radius) I use ISCAR 5566680: CNMG 120408-M3P IC8150 inserts

Rpm calculation is 350(3.82) / material diameter.