Forcing Cones Question

[EddyDehmer]

I have a 12-gauge DHE that I’m looking at extending the forcing cones to achieve 2 3/4” is there any recommendations on minimum breach to barrel thickness that is recommended to make sure you are not ruining the gun? I was trying to find some information on this before I have this work done to the gun.

Thanks Eddy

[Milton C Starr]

Not sure how helpful this is but ive seen other forum members say Kirk Merrington can evaluate your barrels and tell you what is or is not possible .

[David Gehman]

Don’t do it, why take a nice DHE and violate it. Shoot proper shells in it. Yea may be more expensive, but really how many shots do you shoot through it, not withstanding SC.
If you want to shot big shells get a proper gun. Just my feelings, but at this time you are the caretaker of the gun.

[Rick Losey]

I agree, you don’t need to do it

But Just a small terminology point

You would need to lengthen the chambers to accept 2 3/4, it’s not just the forcing cone

[Daniel Carter]

What does the chamber measure now?

[Drew Hause]

1. There is no justification for lengthening 2 5/8" chambers to 2 3/4"
2. There might be some advantage in lengthening vintage 1/2" - 5/8" forcing cones...BY AN EXPERT. Done wrong = ruined barrel

http://pic20.picturetrail.com:80/VOL1373/6511424/24519472/408857932.jpg

Scroll down about 1/3 here for a summary of Sherman Bell's study which suggested than pressure might be decreased somewhat with a longer cone.
https://docs.google.com/document/d/1ZIo0y746UsSRZIgRuuxwAbZjSBHitO_EanvwLYc-kGA/edit
Because the angle of the cone is greater than the external taper of the barrels, in thick walled U.S. maker's 12g (but possibly not light British 12g game guns or small bores) there is usually greater wall thickness in the cone than at the end of the chamber (breech to right)

http://pic20.picturetrail.com:80/VOL1373/6511424/24519472/414172908.jpg

I still wouldn't do it ;)

[Garth Gustafson]

Have your barrels inspected by a knowledgeable double gunsmith for safe wall thickness and be sure to shoot loads the gun was designed for. No need to lengthen chambers. This load data sheet has been posted here before.

[Rick Losey]

I am always surprised to read that there was not much difference between paper and plastic 2 3/4 hulls when used in 2 5/8 chambers- to my non expert mind - I tend to think the thinner plastic hull would result in less pressure all else being equal

[EddyDehmer]

Currently the barrels are at 2 9/16" when I measured them. Originally when the gun was purchased it was stated to be a 2 3/4" shotgun. Remington era after they took it over from Parker. However the barrels were not what was quoted. So I did get a very sizeable refund and the from the all the specs everything lined up in the books on the serial numbers across the board on the entire gun. I was looking for a newer Parker so I can reload 2 3/4" as I do a fair amount of waterfowl and pheasants that needs steel so obviously I buy RST shells in Bismuth. I have another DHE that is an older gun around the 1908 timeframe that is 2 9/16" that I love to shoot and the barrels all tested exact per purchasing. My question would be where do you send barrels to get looked at. I do have a barrel thickness gauge and I do measure the barrels, breach, etc. But where do you send barrels off to get inspected for cracks etc. I want to keep the integrity of the original state, but you have to go through a lot of guns to find guns that have not been tampered with. I appreciate all of your ideas and thoughts.



1. There is no justification for lengthening 2 5/8" chambers to 2 3/4"
2. There might be some advantage in lengthening vintage 1/2" - 5/8" forcing cones...BY AN EXPERT. Done wrong = ruined barrel

http://pic20.picturetrail.com:80/VOL1373/6511424/24519472/408857932.jpg

Scroll down about 1/3 here for a summary of Sherman Bell's study which suggested than pressure might be decreased somewhat with a longer cone.
https://docs.google.com/document/d/1ZIo0y746UsSRZIgRuuxwAbZjSBHitO_EanvwLYc-kGA/edit
Because the angle of the cone is greater than the external taper of the barrels, in thick walled U.S. maker's 12g (but possibly not light British 12g game guns or small bores) there is usually greater wall thickness in the cone than at the end of the chamber (breech to right)

http://pic20.picturetrail.com:80/VOL1373/6511424/24519472/414172908.jpg

I still wouldn't do it ;)

[Garth Gustafson]

Pat Laib in Spicer, MN works on Parkers and he can inspect and measure your barrels. Kirk Merrington is in Tx and he comes highly recommended. For a complete list of member recommendations see the FAQ section on the PGCA home page.

[EddyDehmer]

Garth, thanks as I have to run another gun up to Pat Laib as he has checked my first Parker I originally bought. I appreciate the help with this. Do you know where people send barrels out to get inspected for cracks that can’t be seen? I’m just curious about that.

[Garth Gustafson]

The experts will chime in but typically cracks are much less of a concern with modern fluid steel barrels than with Damascus or twist barrels. A visual inspection and measurements by a qualified smith for bulges, deep pitting and any imperfections in the metal combined with the use of reasonable loads should put your mind at ease.

[Bruce Day]

All this concern over a 5 percent chamber pressure increase ?

[Drew Hause]

http://parkerguns.org/forums/showthread.php?t=29213

[Bruce Day]

Who would have thought that MRI analysis of a Damascus or Twist composite barrel would show hundreds of linear density differences?

[Drew Hause]

No steel in the Magnetic Resonance Imaging room Bruce. That donut thingie is a giant magnet :eek:

This is a negative image radiograph (X-ray; not MRI) of a damascus barrel. The difficulty is in differentiating pits from defects within the wall.

http://pic20.picturetrail.com:80/VOL1373/6511424/24519472/408815326.jpg