Barrel too small for 1/2" threadding?

[cohunt]

Unfortunately, some people buy a light weight barreled rifle because they want the rifle as light as possible. The down side of this is recoil
due to the light weight and then they decide to go with a muzzle brake to tame the recoil, or load up the but stock with weight (Which defeats the original reason for buying a light weight rifle. Most light weight rifles come with small contours two small to safely install a threaded brake.

I hate the looks of the clamp on brakes, but they are an option to prevent weakening the muzzle for light weight barrels. I have also seen a few of these light barrels split from the muzzle end that apparently was not restricted and split along the rifling. The typical muzzle pressure is 18,000 to 22,000 PSI unless you are using a slow burning powder that cant be consumed by the cartridge/ barrel combination producing more pressure at the muzzle. when a fire ball comes from the muzzle, this normally means that all of the powder is not burned in the barrel and pressures can be higher at the muzzle.

Also most light weight barrels were not designed for a muzzle brake and have just enough barrel wall for the cartridge used.

J E CUSTOM

I found some info online about muzzle pressures--of course this is different depending on what bullet weight, powder burn rate, barrel length, etc--but it is a generalization of information to chew on: in a magnum cartridge, the muzzle pressure would be in the neighborhood of 18000psi, but with an 30-06 it would be around 10,000 so clearly there is a large difference in muzzle pressure and therefore a difference in "safety factor" when trying to figure out if 7/16" threads would be safe for a .308 bore rifle

if you use your metallurgy numbers of minimum wall thickness for 50,000psi=.123", and 60000=.148"--then for 10000psi it would only be .025" so in effect, .308+.025"+.025"=.358"-- the minor diameter of a male 7/16" thread is .3949" so technically it would be safe for 308w or 30-06 but for magnums with a muzzle pressure of 18000ish you would need around .045" minimum--which is the minor diameter of unef 1/2" threads

 

[DSheetz]

There are a number of outside influences that play into the grain structures of any given metal .2 1/4 chrome molly has a temperature range for working it as does 416 Stainless steel . They will both work harden as well once you have changed the micro structure then they will need to be heat treated to naturalize the grain structure . Cutting threads will most likely not alter the grain structure by heat but can work harden the metal a good sharp properly ground cobalt cutting tool with a good quality cutting fluid and paying attention to the depth of each cut will not compress the metal or over heat it . Using a die to cut the threads can and will often compress the metal and cause heat to build up as well as not give you a relief at the shoulder where the threads end . It takes time and experience to learn how to grind cutting tools and use them properly that is why we have trade schools and apprenticeship programs for craftsmen as well as all the differing metallurgy that goes into the trades that go into being a good crafts person .