Chamber / Forcing cone

[Wayne Beals]

Please excuse me as I'm new. Would it really hurt the value of a Parker Trojan with a 2.5" chamber to lengthen the chamber to 2 3/4 and give it long forcing cones?

[Dean Romig]

If it's a 12 gauge probably not, unless it's in really nice condition. You wouldn't need to lengthen the forcing cones beyond the approximate 3/4" that were about the standard length. Incidentally, 2 5/8" chambers was the length for 2 3/4" shells and the 3/4" cone beyond that. The shell opens 1/8" into the beginning of the cone giving it a better gas seal.... or at least that was the school of thought when paper shells and fiber wads were standard.





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[Jay Gardner]

I would think so, especially if the gun is otherwise in good condition. With the availability of 2.5” ammo there really isn’t any reason to lengthen chambers and cones.

Best,

Jay

[Garry L Gordon]

With all the knowledge we have gained over the recent years on this issue, and with the great ammo available, I don't believe it's necessary to alter an original gun. Whether it changes the value negligibly or not seems a distance second question to keeping the gun in original condition. Then, there's the issue of getting someone truly competent to do the job.

[Bill Murphy]

An absolute waste of money to drill metal out of a perfectly good shotgun barrel, from either end.

[charlie cleveland]

are you sure the chamber is 2 1/2 it s probably eihter 2 5/8 or 2 3/4....if its a steel barrel gun i bet its longer than 2 1/2 inches...charlie

[Bruce Day]

Are you sure you need to lengthen the chambers when all you get is a pressure reduction of about 300 psi?

[Dave Noreen]

If it was intended for the 2 1/2 inch paper 20-gauge shells of the day it is going to be about 2 3/8 inch. That is what my 1930 vintage Parker Bros. VH-Grade is and a couple of my 20-gauge Ansley H. Fox doubles.

[Craig Budgeon]

Wayne, what problem are you trying to correct by lengthening the forcing cones? Removing material without a sound reason makes no sense.

[todd allen]

My understanding is that lengthening forcing cones takes a gun out of proof. Tapering forcing cones, does not. Not saying to do one thing or the other. That's was I've been told by Briliey's, regarding an old H&H that I had acquired.
That said, (especially when dealing with otherwise original Parkers) my position is; do no harm.

[Bill Murphy]

Tapering? Lengthening? What's the difference? Both are removing metal.

[Brian Dudley]

Do we even know what gauge the subject gun is???

[John Dallas]

There's no "Proof" in the US.

[Craig Budgeon]

There maybe no proof houses in the U.S. but manufacturers would be under constant litigation if they chose not to prove there guns.

[todd allen]

There's no "Proof" in the US.

I was referencing the H&H in the post. It came to me with 2 1/2" chambers. Briley's recommended tapering, as opposed to lengthening the forcing cones.
They told me that tapering the cones would not weaken the chambers.

[Russell E. Cleary]

Yes, how does one taper further what is already tapered without removing the material involved?

My crude rendering here of what I understand of Parker gun barrels (as per THE PARKER STORY and Larry Del Grego and Son).

[Drew Hause]

Because the angle of the cone exceeds the angle of the external taper of the barrel, there is more wall thickness within the cone than the end of the chamber.
The cone can be lengthened (BY AN EXPERT, who is removing metal) while maintaining a wall thickness equal to the end of the chamber

Courtesy of Hollowell

http://pic20.picturetrail.com:80/VOL1373/6511424/24519472/414147079.jpg

Lengthened chamber with the blacked in portions being the metal removed in the process.
Upper side shows a 5 degree angle to the cone. Lower side shows the cone cut parallel with
the outer wall yielding a cone length of approximately 1 1/2".
Courtesy of Miller Fulks as posted on DoubleGunBBS

http://pic20.picturetrail.com:80/VOL1373/6511424/24519472/414167872.jpg

This is a cross-section of a chamber lengthened from 2 5/8" to slightly longer than 2 3/4".

http://pic20.picturetrail.com:80/VOL1373/6511424/24519472/414172909.jpg

This MAY NOT APPLY to small gauge or light weight British 2 1/2" chamber game guns.

Bottom line IMHO is a 12g No. 2 frame "shooter" Trojan with a 2 5/8" chamber could safely have the cone lengthened by an expert.
I'm not aware of any benefit in doing so.
I would NOT mess with the chamber or cones of a short chamber 20g.

[Joe Graziano]

As I think you can see, among those most knowledgeable, if your gun is deemed safe to shoot by a competent gunsmith, have fun and shoot it. No need to mess with the chambers.

[Craig Budgeon]

The photo of provided by Drew depicts a badly chattering reamer and the taper does not appear to be concentric with the bore.

[William Davis]

Early in my Parker education I bought a Trojan 16 with Lengthened Chambers. It’s probably worth half what I paid, and the the guy that lengthened is out his cost to alter. Aggregate loss of value 500-750 even 1000 dollars.

The gun would have handled correct ammunition fine. RST or Reloads using published Hodgdon 2 1/2 inch data.

William

[Wayne Beals]

Its a 12 bore. I was thinking that lengthening the chamber / forcing cone would allow me to shoot 2 3/4 shells without cracking the stock. I have decided to leave it alone and order the 2.5" RST ammo.

[Brian Dudley]

Thanks for letting us know what gauge it was.
The chambers are not 2-1/2”. They are 2-5/8” which parker i tended to shoot 2-3/4” shells from.
So, shoot 2-3/4” shells. Shooting 2-1/2” is only to be cautious, which is fine too if you want.

[Bruce Day]

Sherman Bell, DGJ:

[Bruce Day]

Here’s what I use. The eights are quail or target shot and I use sixes for pheasant, last week limiting on wild not released pheasant.

[Bruce Day]

Or a person can always use the loads that Parker intended to be used:

[John Davis]

I too like the Remington STS light target loads for trap, but prefer them in 1 1/8 oz. (1145 fps).

[Russell E. Cleary]

Drew:

I get your point that “The cone can be lengthened (BY AN EXPERT, who is removing metal) while maintaining a wall thickness equal to the end of the chamber”. And those are very helpful graphics you provide to illustrate the result.

But would not GREATER, not equal, wall thickness tend to be called for when the reducing the area that a powerful charge has to travel in a tube? There is, after all, greater FORCE that is created and has to be contained by a “Forcing Cone”.

Even if lengthening the chamber is going to actually reduce pressures, as Bruce says, maybe by 300 psi, are these trade-offs feasibly calculable so as to determine net benefits when dabbling in invasive surgery on the most important part of any gun (the barrels)?

I know that this is a recurring topic and may well be tiresome for some. But since it relates to safety, i.e., the avoidance of maiming oneself and others, and can have consequences that risk besmirching the reputation of the entire sport, it is worth a solid understanding.

[Drew Hause]

Russ: a couple of very helpful graphs.

This from 1931 shows the pressure-distance curves with vintage powders; FFg, Ballistite (Dense) and Schultze & DuPont (Bulk) and DuPont Oval "progressive burning smokeless powder"

http://pic20.picturetrail.com:80/VOL1373/6511424/24488932/409804775.jpg

The pressure is falling at the forcing cone, though less so with DuPont Oval

Modern powders peak and fall much more rapidly so the pressure at the forcing cone is even lower

http://pic20.picturetrail.com:80/VOL1373/6511424/24488932/412289224.jpg

So there would be no safety justification for more wall thickness in the cone compared to the end of the chamber (where pressure is higher)

And to clarify Bruce's point, Bell's study compared 2 1/2” chamber with a 7/16” forcing cone vs. 2 3/4” chamber with a 1” forcing cone and showed the pressure decrease was about 400-1200 psi depending on the load and vv. the pressure rise could be as much as 1200 psi
A summary is here about 1/4 way down
https://docs.google.com/document/d/1ZIo0y746UsSRZIgRuuxwAbZjSBHitO_EanvwLYc-kGA/edit

[Craig Budgeon]

For the forum members that are not aware there exist 2 types of reamers. There are chamber reamers that lengthen the chamber and reduce the taper of the forcing cone and forcing cone reamers which lengthen the forcing cone only. Your eyes, hands, and gun proceed with caution if at all.

[Joe Graziano]

Y’all are way to smart for me. I just run light 2 3/4 shells through my Parker or I stock up on RST shells at a shoot. If I’m shooting a non-Parker 16 ga with 2 1/2 chambers, I buy 2 1/2 shells. It’s pretty simple, but I’m a simple guy:) Lengthening the chambers costs money, decreases the value and don’t do a dern thing for the shootin. Ain’t gonna do that.

[Ronald Scott]

Or a person can always use the loads that Parker intended to be used:

Is this info in The Parker Story? Thanks

[Drew Hause]

We can even choose loads that reproduce the ballistics of the loads for which the guns were designed

DuPont Ballistic Table published in Parker Brothers' “The Small Bore Shotgun” c. 1920 http://parkerguns.org/pages/PDF%20Documents/Small%20Bore%20Shotgun.pdf
It is clear that this table converts Long Tons to PSI simply by multiplying by 2240; NOT using Burrard’s conversion
p. 7
“All powders referred to on these pages are of the bulk nitro kind ranging from 12 (“New Schultze”, New “E.C. Improved No. 2”) to 13 1/3 (original DuPont Bulk) grains per dram…”
Original “E.C.” and “Schultze” were 14 grains/dram

http://pic20.picturetrail.com:80/VOL1373/6511424/24488932/414020464.jpg

Numbers were measured by crushers and require adding 10 - 14% for modern piezo transducer pressures.
12 gauge
3 Dr. Eq. 1 1/8 oz. = 8,110 psi
3 1/4 Dr. Eq. 1 1/8 oz. = 8,960 psi
3 1/2 Dr. Eq. 1 1/4 oz. = 9,900 psi
16 gauge
2 3/4 Dr. Eq. 7/8 oz. = 7,035 psi
3 Dr. Eq. 1 oz. = 8,980 psi
20 gauge
2 1/2 Dr. Eq. 7/8 oz. = 12,655 psi (Modern SAAMI limit is 11,500 psi)
DENSE Smokeless Powder pressures would be 1000 - 1,500 psi higher

[Daniel G Rainey]

II kill just as many birds with 2 1/2 shells as I do with 2 3/4 shells and with less recoil.

[Drew Hause]

Parker Service and Proof Load table published in the 1930s and reproduced in the "The Parker Story" p. 515. 12g 2 3/4" shell Service Pressure is 10,500 psi. Definitive proof is 15,900 psi or 7.10 Long Tons. The pressure was measured using LUP and modern transducer values would be about 10% higher.

http://pic20.picturetrail.com:80/VOL1373/6511424/24488932/408978095.jpg

[Ronald Scott]

We’re getting off topic from OP but while we’re at it here’s some interesting proofing info from TPS

[Drew Hause]

Thank you Ron. Those Lifter charges are of course for Black Powder and would have run about 1/2 of Bulk Smokeless introduced early 1890s.