Parker DHE 12 ga Damascus Barrels

[B. Dudley]

There is no standard for what wall thickness "should" be. Thickness varies with every gun. Based on the amount of metal was removed in factory striking, and also if they have been refinished or not. The critical spot it around the tip of the forend, this is where pressures are greatest. Check out the couple threads that have been linked in above for more info. Wall thickness must be measured with special tools. Simply checking the muzzle end will not do it.

[Wild Skies]

Originally Posted by Brian Dudley

The critical spot it around the tip of the forend, this is where pressures are greatest.

Are you sure about that?

[Big Friend Ten (BFT)]

Pressure reaches peak in the chamber.

[charlie cleveland]

anybody ever see a gun that just the chamber area or the first 4 inches of chamber that they would deem unsafe to shoot... i have not...charlie

[B. Dudley]

Is it not generally accepted that the critical spot for checking wall thickness is 9-10 " from the chambers?

[Big Friend Ten (BFT)]

I measure the entire length of the barrel in several radials.

Having the forward hand at about 9" from the breach makes it a good place to check, assuming fingers are important.

Pressure is highest in the chamber.

[Big Friend Ten (BFT)]

Jent,

What pressure was the ammo that bulged those three #1 Frame Damascus barreled Parkers?

The term "Light Target Load" seems to denote low recoil and a lower weight of shot rather than low pressure.

Be it high or low, pressure and recoil are not necessarily the same.

[Wild Skies]

Originally Posted by Brian Dudley

Is it not generally accepted that the critical spot for checking wall thickness is 9-10 " from the chambers?

That may or may not be generally accepted, a barrel could have a thin spot anywhere along its length. A thin spot could have been caused by a myriad of reasons such as repairs to bulges, dents or even when it was originally manufactured. Here's a generic drawing of a 12-ga. barrel showing wall thickness contour along its length (all barrels are not created equal and any other barrel is likely to be different than this example), a thin spot relative to the pressure exerted at that spot anywhere along its length could cause bulges or bursts.

[Wild Skies]

Originally Posted by Mark Ouellette

Pressure reaches peak in the chamber.

Here is a chart, verifying what Mark stated, put out by Dupont showing pressure peaks in the first 1"-1 1/2" of the breech and then drops quickly as the load moves down the barrel. Many of us are shooting loads in our Parkers with pressures considerably lower than the loads that were tested by Dupont for this chart. I wonder if our nitro loads that develop ~4000-7000 psi behave similarly?

[Big Friend Ten (BFT)]

Greg,

Thanks for posting the barrel thickness diagram!

Toward what you stated, pressure in a contained space is constant. Since pressure is constant, the weakest (thinnest) area will rupture if the pressure is too high.