doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Lengthening forcing cones....good or bad?

In my opinion, British Proof is a load of manure once the gun exits from the proof house. Brits are famous for grinding the wall thickness from the outside, leaving the inside "in proof". A hundred dollar wall thickness gauge is worth ten times what a proof stamp is worth. Also in my opinion, two identical shotguns, one original 2 1/2" chambers, the other drilled out to 2 3/4", if fired with progressively stronger 2 3/4" bullets, the drilled out gun will burst first. Of course, the drilled gun will recoil less.

I sure have a lot of doubles with original chambers and forcing cones with wall thicknesses way below .100" at the end of the chamber.

Fox A grade 16ga, 26" barrels, 2-7/16" chamber, 0.085" and 0.086" minimum wall thickness at the end of the chambers, .734" and .734" diameter at the end of the chambers, 5/8" long forcing cones, #4 barrels, gun weighs 5lbs 9oz, serial 302XXX.

Parker VH O Frame 16ga, 28" steel barrels, serial 134XXX, 2-9/16" chamber, .082" and 0.085" minimum wall thickness at the end of the chambers, 0.730" and 0.732" end chamber diameters, 3lbs 2oz unstruck barrel weight, gun weighs 5lbs 14oz.

Fox XE 16ga, 30" barrels, serial 301xxx, .072" and .080" minimum wall at chamber ends, 2-7/16" chambers, .733" and .733" end chamber diameters, gun weighs 6lbs 3oz

Parker DHE 16ga, 32" steel barrels, serial 212XXX, 0.090" and 0.092" minimum wall thickness at chamber ends, 2-9/16" chambers, .735" and .736" diameter at chamber ends, barrel unstruck barrel weight 3lbs 11oz, gun weighs 7lbs 4oz.

Lefever H grade 16 gauge, 28" twist barrels, .090" and .092" minimum wall thickness at chamber ends, 2-5/8" chambers, .729" and .728" diameter at chamber ends. Gun weighs 6lbs 4oz

Ithaca Flues Grade 4E 16 gauge, 28" Krupp fluid steel barrels, 0.091" and 0.092" minimum wall thickness at the end of 2-5/8" chambers, daimeters of .728" and .730" at the end of the chambers, gun weighs 6lbs 6ounces.

Parker DH 12 bore, 28" Damascus barrels, 1 frame, .086" and .090" minimum wall thickness at end of the 2-5/8" chambers, gun weighs 6lbs 14oz. Serial #84XXX, My Skeets gauges are in capable of measuring the diameters at the end of the chamber.

Bissel Birmingham boxlock, 20 gauge, 25" steel barrels, made in the 1920s, .084" and .092" minimum wall thickness at the chamber ends, 2-1/2" chambers. My Skeets gauges are in capable of measuring the diameters at the end of the chamber. Weighs 5lbs 7oz.

Best,

Mike

Those dimensions are good reason to not lengthen the chambers, IMO.

I just wanted to make the point that many old doubleguns left the factory with substantially less chamber end wall thickness than .100"

I may want to trade or sell one of these light guns someday and would certainly hate for the general perception to be that they were too thin in the chambers. Bore gauges and wall thickness gauges are becoming ubiquitous and things that didn't used to get checked get checked now.

Best,

Mike

Here is another data point:

AYA #1 20 bore sidelock, factory 2-3/4" (70mm) chambers, 30" barrels, built and proofed in 2006, .092" and .091" minimum wall thickness at the end of the chambers. Skeets gauges unable to measure chamber diameter. Gun weighs 5lbs 13oz.

Best,

Mike

Drilling out a gun with .090 wall thickness at the end of the chambers is absolutely silly. Paying someone to do it is way more than silly.

Just for the record, I am not advocating chamber lengthening. I am contending that old light SxSs shipped from the factory with chamber end wall thicknesses substantially less than .100"

I don't lengthen or have lengthened chambers or forcing cones in my old doubles.

Best,

Mike

Edit - what I meant to say: I don't lengthen or have the chambers or forcing cones lengthened in my old doubles.

Couple more data points:

My shooting student Joe Wood checked his minty Webley 700 6lb 4oz 12 bore, .092" and .090" minimum wall thickness at the end of the chambers. Factory 2-3/4" original chambers.

One of his DH 12 bore 1 frame Damascus 28" barreled guns weighs 6lbs 8oz and has .092 and .095" at the barrels. Original 2-1/2" chambers.

eightbore, your engineering terminology is grating on my nerves.
The rest of you make sure your guns are mechanically sound and just shoot them.
Leave well alone, Greener did most of the experimenting and research and got well paid for it, don't pay someone to experiment and don't waste your life experimenting, get out afield hunting fishing and shooting. Your a long time dead.

They're all unsafe, Mike. Sell them immediately. How many of those guns (other than the AyA) were made after 1930? By that time, we'd switched to higher pressure shells. Lengthening chambers AND shooting higher pressure loads might be a bad combination.

Eightbore, re your comment on British proof . . . the drilled-out gun you suggest would likely burst first (and I think tht's a good bet) would have to be submitted for reproof--where it might have failed without endangering the shooter.