Shotgun converted to .45 suppressed rifle

W

Willie Sutton

Moderator
Been toying with a way to use a Form 1 at home. Have been thinking this over for several years and wanted to share it.

Going to manufacture a barrel insert for a 12 gauge single shot 18 inch BBL shotgun, that will slip into the chamber. The adapter will comprise a .45 long colt chamber, a 18 inch long rifled BBL, and a muzzle centering flange that will keep the entire thing lined up. The BBL will be reduced diameter for the portion ahead of the chamber and to right behind the muzzle centering flange at the front end. I'd port the BBL and machine slip-over baffles to stack over the ported BBL and into the inner diameter of the BBL. Methinks this would make a really interesting subsonic carbine. Fit with some decent sights and enjoy. The hard work is going to be milling a slot in the side of the chamber adapter area for the extractor, and making a longer extractor (or a second mechanism actuated by the existing extractor to be the extractor for the new chamber). I have a lathe and a Bridgeport milling machine so it's not going to be a kitchen table and a file sort of process.

Host weapon would be your average every day available by the dozens at any gunstore for $75 used single shot hammer type 12 gauge shotgun of indeterminite origin... :cool: Really, a H&R type 12 gauge would be the ticket here.

Using .45 LC you would have the ability to push a BIG bullet at subsonic speeds. Call it a "quiet thumper". Rimmed cartridge would be easiest to make an extractor as opposed to .45 ACP, etc. If I really want to make a Thumper, I might actually chamber it to .460 S&W, and use 300+ grain lead bullets at about 850 FPS. Hmmm...... :)


Same system would work for many other cartridges. .38 SPL and .22 LR both come to mind.



Ideas?

Willie

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Shotgun barrel inserts are nothing new. There are several varieties available from simple reducers to competition Skeet tubes. (If you really want to shoot something with big sub-sonic bullets, consider a modern 12-ga repeater with a rifled slug barrel, work-up reduced slug loads, and forget about the .45 Colt. Of course, it wouldn't work with an internal can, and I suppose that's your main idea.) Google Purbaugh tubes to see how the extractors were done before captive extractors became the standard. I agree, a 10-ga would be easier for the can work.
 
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"Sounds interesting if you can make it work. Would a 10 gauge work better?"

More volume for the can (barrel substituting for a can) would naturally be better, but host guns would be very rare. I can't think of the last time I saw a single shot break-open 10 gauge for sale. 12 gauge platforms are as common as dirt. I've looked at the internal volume available, bearing in mind that the length of the can is fairly long, and it's definately adequate. Compared to most of the .45 ACP cans it's positively overkill. The trick will be to space the baffles so that they are positioned correctly while not eating up internal volume. Still playing with that part of the plan.

To the second poster: Yes, I am very aware of BBL inserts of all sorts. While I appreciate your thoughts, they stray very far away from the design idea that I want to persue. It's just one tax stamp cost risked to see how it works. Nothing ventured, nothing gained. I will look at the extractor that you mention.

Any positive ideas on baffle design would be appreciated.


Willie

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One of the biggest problems I see with using a 12 gauge is having enough space. Before you start adding baffles, etc., you need to account for the .45 diameter and the thickness of a barrel strong enough for the 45acp. Don't forget, you won't want any flex in a carbine-length .45 barrel, so it can't be super thin. I would think the outer diameter of the .45 barrel insert would be pretty close to the inner diameter of a 12 gauge. You might have 1/8th inch on either side of the od of the 45 barrel to play with - is that really enough for baffles?
 
First you might try a 12" barrel insert and no baffles. Shouldn't need a tax stamp for that, and you can work on the extractor/ejector. The rest of the (24"?) shotgun barrel will be an expansion chamber; not sure if it needs to be vented or not.

OTOH, the shotgun barrel might make a nice resonator and you can screw a little horn on the end like Sledge Hammer's "loudener" :)
 
Zippy, thanks for the info on the 10 gauge.

Good ideas in the last post, trying a shorter BBl and then adding a stack of baffles on top of that with a retention plug at the end (think threading internally as for a removable choke) might be an option. The trial BBL would be unported as a test-mule for extraction. Great idea!

It's lathe-time... might try .357 just to get more internal volume.....


Willie

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Before I got full length tubes, I shot with short inserts (Savage Four-Tenners). As I recall, there was little difference from the expansion chamber effect.

At the shotgun forum, short 12-ga inserts, in rifle and pistol calibers, are discussed from time to time. As I recall, nobody commented on the sound signature being significantly different when shooting the shorties in 12-ga barrels.

The aforementioned H&R 10-ga comes with a screw-in choke. You might fab a wiper assembly to replace the choke. It could work in most 12-ga guns, too.
 
Thanks... I'm leaning towards a stack-o-baffles dropped in front of the BBL Insert with a screw-in retainer, likely not a wipe in the conventional sense but just a calibre-diameter exit hole. It'll be an interesting project and if it works out, might be a good way to get pistol-caliber carbines suppressed for a reasonable cost.

Willie

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