Author Topic: Rimless 12 guage?  (Read 11521 times)

Magoo541

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Rimless 12 guage?
« on: October 30, 2012, 09:52:11 AM »
I've had some time on my hands (bored out of my gourd waiting for other people so I can do my 2 hours of work) and have been thinking about 3-Gun and the shotguns available.  The limiting issue for mags seems to be the rimmed 12 guage shells.  Anyone ever heard of a rimless 12 Guage?  I am sure its been tried, gun guys are tinkerers by nature.  But I think it'd be the "bees knees" for 3-gun, just need to get a reloading set-up and a supply of hulls along with a gun and mags.  Doesn't seem as impossible a task as it may have been 20 years ago.

Thoughts? Ideas? Comments?
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TAB

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Re: Rimless 12 guage?
« Reply #1 on: October 30, 2012, 10:00:48 AM »
How would you head space them?  You can't use the case mouth.   all the other issuses could be fixed.   
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MikeBjerum

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Re: Rimless 12 guage?
« Reply #2 on: October 30, 2012, 10:19:47 AM »
When comparing a handgun to a shotgun you run into the issue that a handgun case has a given length.  The comparable on a shotgun shell would be the base height.  This would mean to go with a rimless shell the gun would need to be hull specific - High base, low base, medium base.  It could be done, but it would mean a total mindset change and very limited market.

Question:
What is it about the rim that makes it a limiting factor?
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tombogan03884

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Re: Rimless 12 guage?
« Reply #3 on: October 30, 2012, 10:48:22 AM »
If you are careful loading, make sure the rim of the cartridge is forward of the rim below it, you'll have no problem as with the .22 rimfires, Coonan .357 and Saiga 12 guage.

Magoo541

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Re: Rimless 12 guage?
« Reply #4 on: October 30, 2012, 01:10:56 PM »
Question:
What is it about the rim that makes it a limiting factor?

When loading mags the issue Tom mentions above is part of it.  Another issue is with a rimless design, or a rebated rim, magazines could be relatively straight and possibly double stacked to get the capacity up.  I've seen rotary mags that have 4 separate tubes that you can index which is cool but to swap those "magazines" out has to be time consuming where a box magazine would be a lot like a carbine mag change.  I've had some time to exercise my Google-foo and everyone is concerned with head spacing but I thought shot guns head spaced of the rim, why couldn't they head space off the base or rebated rim?

This is more a thought excercise that may lead to something else because I'm bored  ;D
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Re: Rimless 12 guage?
« Reply #5 on: Today at 12:31:47 AM »

Solus

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Re: Rimless 12 guage?
« Reply #5 on: October 30, 2012, 01:38:56 PM »
When loading mags the issue Tom mentions above is part of it.  Another issue is with a rimless design, or a rebated rim, magazines could be relatively straight and possibly double stacked to get the capacity up.  I've seen rotary mags that have 4 separate tubes that you can index which is cool but to swap those "magazines" out has to be time consuming where a box magazine would be a lot like a carbine mag change.  I've had some time to exercise my Google-foo and everyone is concerned with head spacing but I thought shot guns head spaced of the rim, why couldn't they head space off the base or rebated rim?

This is more a thought excercise that may lead to something else because I'm bored  ;D

There needs to be something to physically stop the forward travel of the round at the right place to assure proper headspacing.

Since there are multiple base sizes, the chamber can't be made to have a physical stop for all different lengths.

A rebated rim on a rifle cartridge is to allow something for the extractor to grab.  The round would most likely heads pace on the shoulder.

Semi-auto pistol cases like the .45 ACP head space on the front edge of the case.  That is why a taper crimp is used on them rather than a roll crimp.

Some cartridges are belted ..a band around the case ahead of where the rim would be.  It is used for head spacing...and would probably result in the same issues as the rimed shell when used in a magazine.

Any of these methods would require a new standard for shotgun chambers and the separation of the 'old' design ammo from the 'new'...  a major undertaking and potential safety hazard.  
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fightingquaker13

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Re: Rimless 12 guage?
« Reply #6 on: November 02, 2012, 09:29:41 PM »
How much ammo do you want to carry? The Saiga 12s seem to have a pretty good rep and have a ten round mag you can get. Much beyond ten rounds of twelve gauge and its going to get heavy, rims or no. I'd rather carry 4 or five mags in a tac vest or the like than have one monster  drum type deal. Plus, the saigas are relatively cheap (not so much for the ten rounders though).

tombogan03884

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Re: Rimless 12 guage?
« Reply #7 on: November 02, 2012, 11:24:33 PM »
The Saiga can also use a 20 round drum but they were $140/ea last time I checked.

fightingquaker13

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Re: Rimless 12 guage?
« Reply #8 on: November 02, 2012, 11:29:25 PM »
The Saiga can also use a 20 round drum but they were $140/ea last time I checked.
Yep, and you can load and fire at least four ten rounders in the time takes to reload that drum, plus no reliability issues. I'd rather have several stick mags to one drum any day.

tombogan03884

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Re: Rimless 12 guage?
« Reply #9 on: November 03, 2012, 10:32:34 AM »
I'm not recommending it, I'm just saying it's available.
For the price of 3 you could get another Saiga .

 

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