Breech wall thickness

[Ezra]

Guys,

Is there a general consensus regarding minimum breech wall thickness on currently made barrels?  I know there are different types of steel used, but is there a kind of accepted rule of thumb?  Specifically for a rifle.

Thanks.

Ez

[Acer Saccharum]

I don't think there is anything published, to my knowledge.

Original thin walled fowler barrels usually have very heavy breech sections. Rifles were generally pretty stout-walled, too. This may have been because the metallurgy was not as good as it is today. While there may not have been a lot of rocket science behind barrel design, the was a lot of proof testing and documentation.

You're also not going to get someone on the ALR recommend a minimum wall thickness. Too many unknowns, and too much liability.

[Ezra]

Yes Acer, you are probably right.  Besides, someone was kind enough to send me some common sense guidelines to go by via PM.  I will not go smaller than any current barrel-maker will with the specific steel they use.   Better to err on the side of safety always.  

Ez

[Ryan McNabb]

Look at the dimensions for the lightest currently made barrels...the thinnest contour with the biggest bore.  That will give you a rough idea of what the professionals are comfortable sending out the door to be loaded by the general public with who knows what kind of charge.

[galamb]

Most of the barrel makers will make a 45 cal with a 13/16" barrel.

If you allow for the rifling, say .012 per side, plus the "hole" (.45) that would leave =

(13/16) .8125 - .45 = .3625" - .024" = .3385"/2 for a wall thickness of .16925 (without any dovetails cut etc).

A 7/8" (.875), 50 cal, with .016 rifling likewise would be .875 - .532 = .343/2 for a wall thickness of .1715"

So it "would seem" that the current (commercial) BP barrel makers will not go thinner than .170'ish inches for a wall thickness.

[Mark Elliott]

This isn't directly related to your question, but Don Getz told me once that in designing barrels,  they assume a dovetail slot depth of .040".   That is probably a more important number to keep in your head as a gun builder.    I have process for hand cutting dovetail slots that normally produces a slot of .040".   I was chiseling a little low on the last barrel I worked on and ended up with slots uniformly .045" deep.   It , of course, was an A weight barrel.  I never go deep on heavy barrel.   

[stuart cee dub]

On thin walled barrels like the .50 cal at 7/8'' and .45 cal at 13/16th those walls
don't offer much support  for a threaded percussion drum ,best to concider them suitable for flint only . Others have suggested that a patent breech might be OK if you wanted a percussion gun . I took that advice .Better safe than sorry.