Is this to thin to be safe?

[Dean Weber]

This has been an interesting topic for me for years and I have kept a log of all guns I have measured. I believe the OP is getting reasonable and valid responses from others.

That said I have always been amazed at some of the measurements I have found (using Hosford gauge) on original chambered guns between chamber and forcing cone. Here are a few which cause me to ponder my personal limits since I would consider these original chamberings.

**Measured at point between chamber and forcing cone

1894 Parker (Dam) 16 gauge, 0 frame, 2 1/2 ch - .070/,075
1923 Parker (fluid) 16 gauge, 1 frame, 2 1/2 ch - .084/.084
1905 Parker (Dam) 16 gauge, 0 frame, 2 1/2 ch - .088/.096
1902 Parker (Dam) 20 gauge, 0 frame, 2 1/2 ch - .086/.089
1920 Parker (fluid) 20 gauge, 0 frame, 2 1/2 ch - .080/.097

I am in no way giving advice on personal limits. I am just pointing out there are original Parker small bores without modification which would not conform to some of our personal limits.

[B. Dudley]

Shooting a gun does not wear down the wall. The walls get thinned out either by honing, backboring, exterior refinishing or… they were just made that way.

An obstruction will blow out a thin walled barrel and also a heavy walled barrel.

You need to get measurements at other more critical locations on the barrel set to make a completely informed decision.

[Cold Spring]

Here's a pic that follows on my post of yesterday. C-Grade Fox 12 ga with Krupp steel barrels, honed oversize by a hacker despite agreeing to a lesser overbore. Before the work he claimed to have a precision Sunnen hone but miking after the work showed an irregular succession of thin spots here and there. Wall thickness on this tube was .018" at the leade of its choke, and less that 50 shots with lighter factory ammo caused the bulge with its heavy choking. The other barrel was .020" thickness at the choke leade and it also bulged. As I'd posted .... lesson learned on thin barrel walls along with heavy choking; and who to trust for barrel mods. After this episode all my necessary bore honing has been done by Briley. Always uniformly dead nuts on sizing as requested.
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[Clark McCombe]

So, plan is to get a Hosford gauge, measure barrels, especially those where the chambers are 2 3/4, and not have any more work done to them.
Shooting them will not wear them out.
Use only light loads, even in repro Parkers.
As I am learning, heavier really doesn’t mean any better to break a clay.

[Double Lab]

Originally Posted by Clark McCombe

So, plan is to get a Hosford gauge, measure barrels, especially those where the chambers are 2 3/4, and not have any more work done to them.
Shooting them will not wear them out.
Use only light loads, even in repro Parkers.
As I am learning, heavier really doesn’t mean any better to break a clay.

Now you got it. Especially the not needing heavy loads to break a target and beat your shoulder.

[Mike of the Mountain]

Originally Posted by Clark McCombe

So, plan is to get a Hosford gauge, measure barrels, especially those where the chambers are 2 3/4, and not have any more work done to them.
Shooting them will not wear them out.
Use only light loads, even in repro Parkers.
As I am learning, heavier really doesn’t mean any better to break a clay.

Now you’re digging where the taters are! For 12g, keep the loads 1 oz or less and ideally around the 1150-1180 FPS range and you’ll have soft shooting and a scoresheet full of XX!!

[Craig Larter]

I believe Jon Hosford recommends .090 minimum in front of the chambers on 20 and 16 ga guns.

[Dean Romig]

I should post a picture of Oscar Gaddy’s assessment of my Damascus 16 gauge barrels back in about 2005 or so. I have it at home but I’m not there right now.
And he signed his name to it.




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[Steve Hodges]

Dean, please post when you have a chance

[Drew Hause]

Here ya' go Dean. You sent me this long ago.
I would be less enthusiastic than Dr. Gaddy about a .066" end of chamber wall thickness. We are blessed today to have lots of measurements with which to determine original factory numbers, and that's the lowest (of non-chamber lengthened) I've seen.
That said, it is difficult to get the wall thickness gauge pin exactly at the end of the chamber. And because the angle of the forcing cone is more acute than the external taper of the barrel, forcing cone numbers are often slightly more than the end of the chamber