DOM tubing is sometimes called "seamless" tubing but it is not seamless.
DOM tubing is also not a forged steel product.
DOM tubing is a butt welded tube made on an automatic welding machine which forms flat stock into a tube with the ends meeting. The welding fuses the two ends together. Following welding, it is draw over a die and a mandral to size the tube and to remove the visual and measurable weld bead resulting in a smooth uniform appearance with its size controlled to the tubing specification requirements.
This sizing is important because many fittings require a accurate, smooth diameter in order to seal with conventional fittings.
Most DOM tubing is made from low carbon 1020 or 1026 steel or a 300 series stainless steel.
The most common alloy steel tubing is made from 4130 steel which some refer to as chrome-moly tubing.
While 4130 can be a very strong steel it must be heat treated to obtain high strengths. The condition usually supplied as tubing is in its annealed condition which is about 60 percent stronger than 1020 steel. (98KSI vs 61KSI).
The potential problem with trying to build a gun with 4130 tubing is getting reliable certifications for the material. Without these certs, it is almost impossible for the average person to know if it really is 1020 or 4130.
On the question of using DOM tubing as the basis for a gun barrel one must realize that the published numbers for pressure ratings for tubing is referring to room temperature static pressures.
I've heard form numberless folks who say things like, "This tubing is good for 10,000 pounds per square inch so it must be good enough for a muzzleloader." What they don't realize is that 10,000 psi static pressure is one thing but the pressures guns are subjected to are far from static.
Even the most basic of formulas for calculating tubing strengths and wall thicknesses stresses the need to multiply the expected pressure by 4 if an explosive pressure is being considered.
Said another way, that 10,000 psi (static pressure) tubing becomes 10,000/4 or 2,500 psi tubing if it is being used as a gun barrel.
Most of us on the forum are well aware of the fact that pressures as high as 20,000 psi (and higher) have been observed in a .45 caliber muzzleloader loaded with black powder and shooting a slug.
The more complicated formulas delve deeply into the fluctuations in pressures and the speed of these changes and yes, they too use pressure correction factors of 4 or higher in their calculations.
For these reasons and more I do not recommend using real seamless tubing as a basis for a gun barrel and DOM tubing rates a poor second to real (and very expensive) seamless tubing.
The bottom line in my book is why would someone want to use DOM tubing for a gun barrel? To save money?
That $100 or $200 savings can easily be wiped out in a heartbeat by the $1,000's expense of having ones face reconstructed or being subjected to a life in total darkness because their eyes were blown apart, not to mention arms that don't work or even death.
Trying to save a few bucks on a gun barrel at the risk of these happenings (and worse) is often called, "being penny wise and pound foolish".
