12L14 steel strength

[Col. Batguano]

So what thickness is necessary at what pressure so that we aren't doing destructive testing when we shoot these things?

In other words, what pressure will make it fail at .010", which is what a lot of people feel is a minimum thickness to leave for barrel lug and sight cuts?

Similarly at .015, .020 etc?

 

[shguns]

Interesting question.
While I am aware of those that say it is not barrel steel at any thickness, I am also aware that well regarded barrel makers continue to use it. :stir:

 

[Vaino]

It seems you have your decimal points wrong....010, .015 and .020 thicknesses would fail w/ very little pressure. Do you mean .100, .150 and .200?

 

[Zonie]

If we are asking about what thickness does 12L14 steel need to be to prevent failure there is no one set answer.

The required thickness is dependent on the caliber, the internal pressure and the safe tensile stress per square inch of the material.

There are also several different formulas which are used and the proper choice depends the ductility of the material being considered.

I might add that the formulas are not simple and the resulting answer must be modified by multiplying it by the proper safety factor.

The typical safety factor for containing an explosion like black powder produces is 4.

 

[rich pierce]

Back in the day Don and John Getz breeched some short 12L14 barrel sections at both ends, drilled touch holes, loaded them, screwed on the breech, and lit the fuse. I hear they really banged around the room. No shrapnel. No failure. The big problem with barrels is when they are short started then fired without ramming the ball home. I don't worry about 12L14 barrels properly loaded. I worry about any barrel steel improperly loaded.

Regarding barrel wall thickness, it's thickness at the breech that matters when loads are rammed home properly. Barrels can be 0.062 at the muzzle like a nice fowling barrel with no problem.

 

[galamb]

12L14 is not a barrel steel - believe it is listed for making screws etc.

But, also as noted, with the exception of Green Mountain (and perhaps one or two other very small/less prolific operations), just about every black powder barrel out there is made with 12L14.

You get slightly differing opinions but the minimum wall thickness I have found recommended is .050" (usually the amount of "meat" recommended to be left under a dovetail or blind hole for a screw or a staple) - personally I don't go thinner than .080" - just because.

It is "tough" (but not impossible) to get more than 25,000 psi with most of the standard calibers using "reasonable" charges and in most cases the pressure is probably a little south of 15,000 psi.

Just about all of the barrel makers out there producing their barrels with 12L14 will go no "thinner" than .160-.170" at the breech.

So either someone has done some testing they are privy too or maybe that's just a rule of thumb.

I do know that Don Getz did some testing where, among other things, he installed a plug in both ends of a barrel and then touched it off and still didn't split the barrel (pressure came out the touch hole).

There are some that will tell you that 12L14 is totally un-suitable and should never be used for a barrel under any circumstance.

Unless you are willing to do your own testing, which then may only be applicable to the particular batch of metal used in the specific barrels you tested, I would simply stick to .170" wall thickness at the breech and minimally .050" of metal between the rifling in the bore and the bottom of a dovetail etc.

That formula seems to be working for the thousands of ML's out there shooting upwards of 120 grains of powder in the common calibers...

 

[M. De Land]

We hashed this around about a year ago or so and it seems to reappear from time to time.
12L14 has very poor shock load numbers but machines very well. It is brittle compared to other more suitable barrel steel.
I use Green Mountain barrels as they are made of 1134 a much more suitable alloy for barrel steel with very good shock load numbers. Mike D.

 

[Doug Lykins]

Okay, somebody fill me in.....why would ML barrels be made with a type of steel that is different from other rifle barrels? :hmm:

 

[Rifleman1776]

Here we go again.... :stir: :stir:

 

[Rifleman1776]

It is brittle compared to other more suitable barrel steel.

:nono: Destruction tests I have seen, including in Muzzle Blasts years ago, show the 12L14 barrels splitting to relieve gasses. Modern GBQS steels shattered like glass.

 

[jamesthomas]

Here we go again.... :stir: :stir:

Yep, once again the :stir: gets stirred. I have no problems what so ever using 12L14 for my gun barrel.

 

[Rifleman1776]

just about every black powder barrel out there is made with 12L14.

Yep, fer certain, fer sure.
BTW, I do wonder if tests have ever been done with original soft iron barrels. :hmm:
Or did they all blow up? :rotf:

 

[matt denison]

So what thickness is necessary at what pressure so that we aren't doing destructive testing when we shoot these things?

In other words, what pressure will make it fail at .010", which is what a lot of people feel is a minimum thickness to leave for barrel lug and sight cuts?

Similarly at .015, .020 etc?

Too many variables in your question. First I assume that you mean .100" rather than .010". That would depend on where it is on the barrel in relation to the breech. Breech wall thickness should (IMHO) be close to .200" (two tenths of an inch) Farther down the barrel where preasure drops off it is safer to dovetail in a sight or underlug at, say 9-11" from the breech. Pressure drops dramatically after 10 or 12 inches so having those .050 deep dovetails aren't so critical. I don't know of any certified testing having been done to compare 12L against 1137 either with or without dovetails in the barrels.

Mr. Getz tried to blow a piece of 12L and failed. I also tried to blow one of my barrels with 240 gr. FFg and double patched ball. Did not change any dimensions internally or externally. I do believe it would take gross negligence to blow any barrel regardless of what it is made of. Not that it never happens but very rare and probably not the fault of the material the barrel is made of. Just my experienced opinion. :surrender:

 

[jerrywh]

This subject has been hashed over so many times it is pathetic. Zonie is correct. There are many factors and each individual case is different.
There are formulas but to be honest they are over my head. I have four friends that are engineers and I have conversed with them many times about this. I have conducted a lot of tests and have heavily overloaded some very thin barrels but have never had one fail or change
dimensions. all but two of the barrels I tested was made of 12L14 and loaded properly. One was seamless Shelby tubing and was loaded with 600 grains of ffg DuPont three times and three oz. of #6 shot. However a friend of mine blew a barrel up made from the same material with a load of only 80 grains of ffg GOEX. I never used that steel since then , That was over25 years ago.
I have absolutely no fear of 12L14. Or 1137. for black powder barrels.
The shape of a dove tail or a round hole does not weaken a barrel the same as if the whole barrel was that thin in a section. The possibility of the barrel bursting through that small spot is about the same as winning the lotto.

 

[Col. Batguano]

It seems you have your decimal points wrong....010, .015 and .020 thicknesses would fail w/ very little pressure. Do you mean .100, .150 and .200?

I think I did have the dimensions wrong. Thank you. A case in point would be a B-weight .50 cal. Waist thickness is .730. Take out bore thickness of .510 that leaves you with a wall thickness of .110 before cutting in a dovetail. A dovetail might be .030, so that leaves you with .080 at the tangent / thinnest place. Since this is considerably down bore from the breech, the pressure has probably dropped 60-80% from where it was at the breach (based upon an M1 Garand having pressure at the gas hole for the op rod of 10% of breach pressure 23" down barrel). I know BP has a different pressure curve than smokeless, but the theory is the same.

I know for shooting the fundamental rule of; "don't do anything stupid" always applies. I'm just trying to figure out where "stupid is (before) as stupid does" is, and why.

 

[galamb]

Okay, somebody fill me in.....why would ML barrels be made with a type of steel that is different from other rifle barrels? :hmm:

Breech pressures with FFF Goex under a standard roundball:

32 cal, 70 grains = 15,500 psi
36 cal, 70 grains = 15,300 psi
45 cal, 120 grains = 13,300 psi
50 cal, 120 grains = 11,800 psi
54 cal, 120 grains = 11,300 psi
58 cal, 140 grains(FF) = 9,800 psi

Breech pressure of a Winchester 308 = 62,000 psi

Any questions??? :idunno:

 

[kaintuck]

i'm thinking, we should contact the barrel makers...see what they can tel us about the specific barrels, and the safety factor considered by dovetails in they're barrels....
marc

 

[BrownBear]

Always good to go to a source with experience and firsthand knowledge. Listening to a bunch of guys speculate is free, but you get what you pay for.

 

[BillinOregon]

I believe Mr. Bill Moody used 12L14 for his fine muzzleloading target barrels with false muzzles.

 

[Zonie]

Okay, somebody fill me in.....why would ML barrels be made with a type of steel that is different from other rifle barrels? :hmm:

Breech pressures with FFF Goex under a standard roundball:

32 cal, 70 grains = 15,500 psi
36 cal, 70 grains = 15,300 psi
45 cal, 120 grains = 13,300 psi
50 cal, 120 grains = 11,800 psi
54 cal, 120 grains = 11,300 psi
58 cal, 140 grains(FF) = 9,800 psi

Breech pressure of a Winchester 308 = 62,000 psi

Any questions??? :idunno:

Carrying this on a bit, the bottom line is cost.

Barrels made to shoot modern smokeless with its high pressures are made from steels that are much more costly and much more difficult to machine.

These higher strength steels also require special heat treatments that add to their cost too.

The barrels shooting black powder which burns slower and makes lower pressures than smokeless powder do not need to be special high strength materials.
Many common types of steel will be strong enough to do the job providing the barrel walls are thick enough.

12L14 is very similar to AISI 1025 which is slightly stronger than common 1018 or 1020 low carbon steel but it contains very small traces of lead. The lead makes it much easier to machine without weakening it.

Some say 12L14 is more brittle and to a small degree, they are right.
The brittle nature of a material is gauged by its Elongation properties.
My reference gives a value of 10% for cold rolled 12L14 and 22% for hot rolled 12L14.

For common low carbon steel like AISI 1018, 1020 or 1025, the values are, 15% for cold rolled and 25% for hot rolled.

While on the subject of barrel steels, Green Mountains use of 1134 was mentioned.

This is also a free machining low carbon steel but it has higher tensile and yield strengths than the steels mentioned above.
As for its brittle nature, it's elongation is 12% for cold rolled and 16% for hot rolled making it very similar to 12L14.