Author Topic: 12 Ga. inside barrel diameters.. (Read 555 times)

DonT · « **on:** April 05, 2006, 04:13:58 AM »

Tired of waiting for the Remington 45-70's SXS to get here so I am looking at a "project".

I have recently picked up a Stevens 311D double. My thought was to shorten the barrels to 20". Then turn down a 45cal or 38 cal blank to fit inside one fo the barrels, probably the left one as I am right handed. This would leave the right barrel a cylinder bore shotgun barrel for shot or slugs.

I know the "sleeve" would need to have the shape of a 12ga. shell at the back, minus the rim. Then I would need to figure out how to use the gun extractor to lift the 45-70 (or 38-55) rim which should not be too tough.

What I need to know is if any of you folks know the inside dimention of most 12 ga. barrels (prior to the choke)? I need to see if this will be feesable dimension wise.

My thought would be to anchor the sleeve using Acraglass or one of the other heavy duty epoxy comppounds after using some shims between the inside of the shotgun barrel and the outside of the sleeve to regulate it.

I understand that you will need to stay close to factory limits when it comes to loading so as not to loosen the action, but the Remingtons (if & when the get here) are the same way.

I have done some hobby smithing in the past and have access to a lathe and mill. Gettin tired of sittin on the couch at nite watching the tube and need a challenging, but doable, project. :grin:

Thanks for your help...
DonT

gunnut69 · « **Reply #1 on:** April 05, 2006, 12:18:54 PM »

The nominal bore diameter of a twelve guage shotgun bore is .729 inches. Yours may differ!! In a person thought, I don't believe the project you contemplate is a safe undertaking. Procede at your own risk.

DonT · « **Reply #2 on:** April 05, 2006, 12:47:26 PM »

I would be interested in hearing you thoughts on why you feel it would not be a wise persuit. I always like to learn.

My thought is that Tangliofoli sells a sleeve that slips into a Baikal SXS 12 Ga. for shooting 45-70's in and in essense I am doing the same except making it a "permanent sleeve. The Stevens shtotgun I would use is a 311D which is one of the later models...

I am probably missing something, please I would appreciate your thoughts...

DonT

gunnut69 · « **Reply #3 on:** April 05, 2006, 06:40:33 PM »

Some of the 311's were made with cast iron frames. They were designed to contain 8000 to 9000 PSI tops and most often less. They were were not designed to contain the 15,000 to 20,000PSI loads of the 45/70. Also .729 inches minus .458 gives .271 divided by 2 gives .1355 which gives a barrel wall thickness of just over 1/8 inches. The sleeve has to contain the pressure as the shotgun tube will not be supporting. If the tube ruptures the gas will first be released between the insert and the shotgun tube, which will immediately rupture also.. I believe the iron frame will eventually fail or the insert will rupture. Either would be devastating.. I've some of the older doubles fail while firing standard pressure shotshells of modern make. Even though the thrust area of the 45/70 casehead is significantly smaller eventuall the receiver will fail..and with a cast iron frame the is usually no bending. They simply break or shatter. The reult is much like the WWII pineapple handgrenade, also mde of cast iron. It is possible that modern made doubles constructed of cast steel may stand the strain but they would need be restricted to low pressure loads unless modifications such as bushed firing pins were done to handle more pressure. I guess my concern is that this not only has to survive but has to survive over time. Pressure stresses are repetative and accumulate.. in a receiver not made to handle that level of stress. There is also the liability issue. If this is built and someone does something stupid and fires one of the higher pressure loads in it, the builder and the owner will all end up in court..

DonT · « **Reply #4 on:** April 06, 2006, 03:02:10 AM »

Gunnut69,

Thanks for the valuable information. Guess this project goes into the scrap heap and I will continue to wait for one of the Remington Doubles or look for a one of the combos or drillings.

Again thank you for your sharing your wisdom and input, it is appreciated.

DonT

gunnut69 · « **Reply #5 on:** April 06, 2006, 06:32:09 AM »

I've seen this done but would not fire one myself.. I've seen too many fine older doubles destroyed by simply using modern ammo..let alone rifle ammo.. Actually I've an Ithica in the shop now..belongs to a friend. Frame is cracked from the corner of the water table and the standing breach completely around under the receiver. It's undoubtedly ruined. I'll weld it back together for a wall hanger.. No one was hurt by this one but the gun literally fell apart in the field..

gunnut69 · « **Reply #6 on:** April 06, 2006, 06:32:43 AM »

I've seen this done but would not fire one myself.. I've seen too many fine older doubles destroyed by simply using modern ammo..let alone rifle ammo.. Actually I've an Ithica in the shop now..belongs to a friend. Frame is cracked from the corner of the water table and the standing breach completely around under the receiver. It's undoubtedly ruined. I'll weld it back together for a wall hanger.. No one was hurt by this one but the gun literally fell apart in the field..