A Question For Gunsmiths

Major Khan

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Dear fellow forum members ,
I have been reading various articles on the internet and I have found something , which confused me a little .
There are many operators who own double barreled shot guns that originally possess 2.75 inch chambers . However , they make a gun smith lengthen these chambers to 3 inches , in order to accommodate 3 inch cartridges .
I was merely wondering ... Is this not a very unsafe thing to do ? I should think that lengthening a double barreled shot gun's chambers from 2.75 inches to 3 inches would put the gun's chambers and barrels out of proof .
As I am not a gun smith , this concept is a little alien to me .
Any assistance to aid me in understanding how this " modification " works would be greatly appreciated .
Yours sincerely ,
Major Poton Khan ( Retired )
 
I actually went looking for an answer to this very question when I was answering your PM this morning. I found this on one website:

You will run into many short-chambered double-barreled shotguns whose owners would like them rechambered for 3-inch ammunition. Although the barrels themselves would probably hold up to the pressure of 3-inch shotshells, there is no reason to think that the rest of the action could take the extra abuse. Remember, these shotguns were made long before advances in our ammunition propellants that give us the shotshell performance that we enjoy today. Never lengthen the chambers of a Damascus or laminated-steel shotgun barrel.

So it would seem that the question of the barrels/chambers being out of proof is definitely applicable to guns of a certain age/manufacturing technique, and I've heard a number of warnings not to fire the old "Damascus" barrels at all without using low-pressure shells, while there's an overall risk in older shotguns at least of the entire gun failing.

But some shotguns, like a modern pump-action Remington 870, can have its chamber lengthened for 3" shells and operate without trouble, so if it's not a double/single-barrel you'd need to take the action dimensions, ejection port, and gas system on semi-autos into account if you had one of those but the risk is somewhat lower versus older or lower-quality shotguns.
 
You can alter the chambers, from technical point of view this is fairly straightforward but “with great power comes great responsibility”. Can the action and the barrels handle the extra pressure? If I was to do such a thing I’d have the gun reproofed. Why? I have 10 fingers and I like it that way. Any modification to the chambering will invalidate the proof but this is just a legality, the real issue is the gun being able to handle the pressure increase. Some will and some won’t. Also, at this stage there aren’t all that many 3” shells out there. This doesn’t answer your question Major but personally, despite being a very poor scatter gun shot myself I don’t see a point of going above 2 3/4” in a 12G for hunting. If this isn’t sufficient enough a load than probably the problem is elsewhere, either the shooter misses, the choke/distance/shot size is very wrong or a whole different gun is needed. Few extra grams of shot won’t help.
 
I agree 9 1/2 fingers is not fun.
The only reason I go above 2 3/4 is when using steel shot, which is hard on the barrels of a side by side. So when I hunt waterfowl, I use 3 1/2 shells in a Remington 870 Super Mag.
 
The only thing I use a 3” 12 ga for is in a Remington 870 I have set up with a short full choke barrel and holographic sight strictly for wild turkey hunting. 3” #5 or #6 buffered loads. Ducks and geese my family won’t eat, so I don’t hunt them.
2 3/4” shells worked fine for many many years. As you increase the shot load, the shot column lengthens with more bore scrub deforming more shot causing worse patterns. JMO
Poton, please don’t mess with that fine Belgium SxS of yours! Buy another designed for 3” if you really need one! Again, JMO!
 
I agree 9 1/2 fingers is not fun.
The only reason I go above 2 3/4 is when using steel shot, which is hard on the barrels of a side by side. So when I hunt waterfowl, I use 3 1/2 shells in a Remington 870 Super Mag.

If the gun is strong enough why not, rifles run much higher pressures anyway but when converting a gun to handle higher pressures caution is advised. Some can do it easily others not so much.
 
I just don’t use anything more than a 1 1/8 ounce target load or 1 1/4 high brass for hunting, bar waterfowl. I never saw a need. For waterfowl we must use non toxic shot, I use steel. With Patternmaster chokes (non restrictive) I get good patterns. I use the 3 1/2 shells to keep the pellet count up with the BBB shot for geese
 
The only thing I use a 3” 12 ga for is in a Remington 870 I have set up with a short full choke barrel and holographic sight strictly for wild turkey hunting. 3” #5 or #6 buffered loads. Ducks and geese my family won’t eat, so I don’t hunt them.
2 3/4” shells worked fine for many many years. As you increase the shot load, the shot column lengthens with more bore scrub deforming more shot causing worse patterns. JMO
Poton, please don’t mess with that fine Belgium SxS of yours! Buy another designed for 3” if you really need one! Again, JMO!
But Ridge Walker .... my " Old Belgian " already has 3 inch chambers from the very beginning . Look .
FB_IMG_1575727191567.jpg

I have been using 3 inch Eley Alphamax magnum cartridges in my " Old Belgian " safely for the last 61 years, with utter impunity .
I was merely asking this question from an academic stand point . While randomly browsing through the internet a few nights ago ... I came across a few pages on the internet , where " aspiring gun smiths " were talking about increasing the chamber length of shot guns with 2.75 inch chambers to 3 inch chambers . I immediately got curious about this , because ( much like yourself ) I could never consider this to be a good idea under any circumstances whatsoever .

ALTER MY " OLD BELGIAN " ?! What blasphemy is this ? I would much rather die than make any so called " modifications " to the grand, old gun which has been giving me more than 61 years of flawless service . I consider it to be 1 of my most prized earthly possessions . Just look at it ! In the last 61 years , I have not even let a single scratch befall my trusty , old shot gun .
FB_IMG_1575727193927.jpg

Ridge Walker , I am truly disappointed in you ! It is like you do not know old Poton , at all .
 
Last edited:
I actually went looking for an answer to this very question when I was answering your PM this morning. I found this on one website:

You will run into many short-chambered double-barreled shotguns whose owners would like them rechambered for 3-inch ammunition. Although the barrels themselves would probably hold up to the pressure of 3-inch shotshells, there is no reason to think that the rest of the action could take the extra abuse. Remember, these shotguns were made long before advances in our ammunition propellants that give us the shotshell performance that we enjoy today. Never lengthen the chambers of a Damascus or laminated-steel shotgun barrel.

So it would seem that the question of the barrels/chambers being out of proof is definitely applicable to guns of a certain age/manufacturing technique, and I've heard a number of warnings not to fire the old "Damascus" barrels at all without using low-pressure shells, while there's an overall risk in older shotguns at least of the entire gun failing.

But some shotguns, like a modern pump-action Remington 870, can have its chamber lengthened for 3" shells and operate without trouble, so if it's not a double/single-barrel you'd need to take the action dimensions, ejection port, and gas system on semi-autos into account if you had one of those but the risk is somewhat lower versus older or lower-quality shotguns.
Why thank you so much , Webley ! It is truly a shame , as to how many unappreciative operators these days alter the chamber length of their beautiful 2.75 inch chamber side by side shot guns to 3 inches , merely because they feel that the 2.75 inch cartridge is not " good enough " . These so called " Shooters " need to be taught a lesson in shooting , they do !
 
I guess some actions would take the 3 inch shells, and some would not. I wouldn’t be willing to take the risk. Just buy a modern shotgun.
I could not agree more , Master Smith . Fortunately , both my " Old Belgian " and the semi automatic Wischo shot gun which dear old Tobin had gifted me ... are equipped with 3 inch chambers .
FB_IMG_1575727193927.jpg
IMG_20191207_175344.jpg
 
The best answer would sound like this: "what u cant kill with a 2 3/4 inch shell, will not die from a 3 inch shell"!!!

But some guns can be altered to a 3" chamber.
This is an inescapable truth , austrianhunter .It is truly a shame , as to how many unappreciative operators these days alter the chamber length of their beautiful 2.75 inch chamber side by side shot guns to 3 inches , merely because they feel that the 2.75 inch cartridge is not " good enough " . These so called " Shooters " need to be taught a lesson in shooting , they do !
 
You can alter the chambers, from technical point of view this is fairly straightforward but “with great power comes great responsibility”. Can the action and the barrels handle the extra pressure? If I was to do such a thing I’d have the gun reproofed. Why? I have 10 fingers and I like it that way. Any modification to the chambering will invalidate the proof but this is just a legality, the real issue is the gun being able to handle the pressure increase. Some will and some won’t. Also, at this stage there aren’t all that many 3” shells out there. This doesn’t answer your question Major but personally, despite being a very poor scatter gun shot myself I don’t see a point of going above 2 3/4” in a 12G for hunting. If this isn’t sufficient enough a load than probably the problem is elsewhere, either the shooter misses, the choke/distance/shot size is very wrong or a whole different gun is needed. Few extra grams of shot won’t help.
You have attempted to answer my question , Opposite Pole .... and that is what counts . And I could not agree with you more . It is truly a shame , as to how many unappreciative operators these days attempt to alter the chamber length of their beautiful 2.75 inch chamber vintage side by side shot guns to 3 inches , merely because they feel that the 2.75 inch cartridge is not " good enough " . These so called " Shooters " need to be taught a lesson in shooting , they do !
 
This is an inescapable truth , austrianhunter .It is truly a shame , as to how many unappreciative operators these days alter the chamber length of their beautiful 2.75 inch chamber side by side shot guns to 3 inches , merely because they feel that the 2.75 inch cartridge is not " good enough " . These so called " Shooters " need to be taught a lesson in shooting , they do !

For most rough shooting, a 28 Gauge is with me - 7/8 Oz. of No. 6s or 5s do the trick easily. Also the .410 works if you know, what you are doing.4

Many instructors tell you when to shoot or how to shoot (forget about them) - the real art of shooting (rifle, shotgun, handgun, ... you name it) is to learn WHEN NOT TO SHOOT.
 
To me a 2.75" gun is preferred. If you want to mess with the insides, check out if it will benefit from. work on the forcing cones. Work on the pattern, work on the shooting. Work on the right pattern for the shooting you do. Are the left and right the correct choke, is the barrel length correct. Regulation. Does the gun fit. Is the action smooth. What about the trigger. Learn to reload shells for pattern optimization. Everything but the shell length.

On the question itself. With relatively similar guns of modern steel, it would probably work out if wall thickness was in a reasonable range. Start by comparing the external diameter in the area of the work. Keep in mind that the tensile strength of the wall is a second order function of wall thickness. What might not seem a like a large difference in barell diameter, is possibly a large difference in wall thickness. And doubling wall thickness will quadruple strength. So look at barrel diameter. If that is encouraging, then you may also want to investigate further. Though I would leave it alone.
 
There is relatively little benefit from using 3" cartridges over 2-3/4" cartridges. There is considerable downside to altering shotgun chambers/barrels. On classic guns barrels are 'tuned' to handle certain shot loads and are so proofed and marked. Altering them will put them out of proof. This will also decrease resale value.

The chamber length and shot load specifications for a gun are mainly about pressure tolerance. I used to trim hulls and make short loads, but I have found that loading 2-3/4" hulls with loads that are match the pressure profile of 2-1/2" loads work very well in my 2-1/2" 12 and 16 gauge Brit doubles. A careful reading of Gough Thomas or Sherman Bell will show that this does not increase pressure levels beyond specifications. It also saves me a great deal of money over buying 'special' cartridges.

I have had (in my youth) a couple of Brit shotguns lengthened from 2-1/2" to 2-3/4" chambers. This move provided no benefit and decreased to value of the gun, as well as putting me at more risk of unwanted 'accidents'.

When I shot a lot of waterfowl (several hundred birds per season) I simply used short magnums (1-3/8 oz. of shot) in my old 2-3/4" chambered Browning Superposed. I ended each season with the second finger of my trigger hand looking like a cooked sausage. Shooting an even heavier load seemed like a bad idea.Still does.
 

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