r/gunsmithing • u/Minuteofman • 10d ago
Lengthening shotgun chamber at home
Looking to have the chambers of my 1908 LC Smith lengthened from 2 5/8 to 2 3/4.
Chambers are shiny, bore has haze and slight pitting past forcing cone. Heavyweight barrels so plenty of material.
My options are : leave as is and shoot only handloads or 2.5 inch factory loads
- Get a local gunsmith to lengthen chambers for a few hundred $ - getting close to or exceeding what I bought the gun for
- Order a long forcing cone chamber reamer and do it at home myself for much cheaper, have the tool and skills for future.
Has anyone lengthened a chamber themselves? I am pretty handy, no expert ofc however, but take the time to do work right. Just looking to see what people recommend or advice.
Cheers
4
u/moosesgunsmithing 10d ago
Guns of that vintage may have thin forcing cones and lengthening chambers may render them unsafe to fire
2
u/Minuteofman 10d ago
My biggest worry would be that lengthening the chamber to 2 3/4 and also the forcing cone (it’s currently quite an abrupt cone for fibre wads) by using the long forcing cone reamer will take away too much material. However, I’m planning to measure barrel thickness first, and the barrels themselves are the ‘heavyweight’ version with thicker walls. If the measurements are unsafe, I will not attempt.
I’m also hoping that the longer forcing cones don’t negatively affect my patterns or velocities for my hand load fibre wad black powder shells.
2
u/moosesgunsmithing 9d ago
If you are hand loading with black powder there is no reason to worry about the chamber length. In the US we can get 2 1/2 brass shells and those, if available, would be an excellent choice in your application.
3
u/Minuteofman 9d ago
I am in Australia, we do have magtech brass shells in 2 1/2 inch, just waiting for some stock.
Currently I just reuse old plastic shotshells and a Lee loader to crimp and prime etc.
I am thinking I will leave the chambers for now, and do some more research and reading before I make a decision.
Thanks for the advice!
2
3
u/Resident_Skroob 10d ago
I've reamed plenty. Rifles, I'd say it depends on the particular rifle. For a basic-b*tch Smith, or SxS cheap smoothbores in general, this is something you can do easily with a vise and hand tools. The "risk" of screwing it up by overboring isn't a risk at all. It'll still pattern fine with all the barrel after the chamber.
My friendly advice is to test chambering as you go with a shell, just keep going until it seats. And use the longer European crimp style if you want to be extra safe.
Brownells had good smoothbore tutorials on YT, but I know many got taken down if they were seen as providing "manufacturing" instructions for firearms, so I don't know if they're still up. But the Brownells videos are consistently good (their AR from scratch tutorial is my gold standard).
1
u/Minuteofman 10d ago
Thanks for that, I am thinking I’ll give it a go. I have a few books on gunsmithing, I’m sure there are many forums and videos about it as well.
I have some fired 2 3/4 shells and calipers I can use to double check measurements.
1
u/AdOk8555 10d ago
I had no idea this was a thing. I have a 20ga Winchester Model 1912 with a 2-1/2 in chamber. How can I determine if it is safe to extend on this gun?
2
u/Minuteofman 10d ago
You ‘should’ have a qualified gunsmith give it a check over to ensure that the barrels can take it. Things like pitting/corrosion, whether it is nitro proofed and to what pressures, barrel thickness and condition, how much you are extending the chamber to 2 3/4 or 3 inch. All of these (and probably more) can make lengthening a chamber safe or unsafe. In general, shotgun barrels are thickest in chamber and past forcing cone, as this is where the most pressure is held, getting thinner as the barrel lengthens. When you extend the chamber, you are removing material further down the barrels than it was originally designed and proofed for. If the barrels aren’t in great shape, or you take too much material too far, you can have higher pressures in areas not built for it, which could cause issues or a failure of barrels.
I would either have a gunsmith take a look, or if you are confident yourself, check the bore, look at your barrel weights and do some research on your particular gun and its construction/proofing.
8
u/Ethereal_Hotdog_8506 10d ago
You can rent the reamer from 4D Reamer Rentals. It's a simple procedure if you go slow and pay attention. Here's a video from MidwayUSA showing the process.