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Making a Shockwave into an AOW - Crazy, Right?!

Hi! This is my first post here, but I have been shooting Mossbergs for years. Sorry to hit you with such a crazy, and involved, first post.

Like lots of people, I love the look of the Shockwave and want one. However, this is not possible in my state due to state laws which define it as a short barrel shotgun, which are prohibited even if you get the NFA $200 tax stamp. However, an "Any Other Weapon" with the tax stamp is specifically carved out from the state law prohibiting SBS. So I can have a Shockwave by (i) importing a PGO weapon with at least an 18" barrel; (ii) getting the NFA $200 tax stamp and complying with NFA requirements about marking receiver, etc.; and (iii) shortening the PGO weapon to below 26". Crazy, right? Can't have the stock 26"+ Shockwave, but I can have one less than 26". But please, I want to keep this thread focused on the gunsmithing and technical specs, so trust me on my state laws and let's don't get sidetracked.

My preference is to do this with minimal gunsmithing, and minimal expense. The expense is going to be astronomical compared to those in states where Shockwaves are legal, but I want to hold it down as much as possible. So I have come up with the following method. Order a stock Shockwave through a "middleman FFL" located in another state (I have located one who will do this). Middleman takes off 14" barrel, replaces it with 18.5" barrel, holds on to 14" barrel, and ships firearm to FFL in my state. I pick up firearm and start the NFA process. Once tax stamp is approved and receiver engraved, etc., middleman ships 14" barrel to me. I then "manufacture" the AOW by swapping out barrels. (I will need to do something else to get OAL below 26." Simplest method initially will be to put a standard "cruiser" type pistol grip on before I put the 14" barrel on it). Voila! I'm legal. Those pumpkins had better watch out, I'm coming for them!

I need to send a barrel at least 18 inches long to my middleman to make this work. I would like to use an 18.5" barrel from a Mossberg 500 I already own, but I'm pretty sure this won't work. The way the barrel attaches to the mag tube is different. I need the firearm to be functioning when imported into my state, although I have no intention of firing it in this configuration, so the barrel needs to attach properly to the mag tube. So I think I need to buy a 590 18" barrel or some other barrel. I can always sell it later and recoup most of the cost. The distance from the chamber end of the barrel to the back of the lug connecting the mag tube is about 14.75" on my 500 barrel. But it can't be that much on a Shockwave barrel since that barrel is only 14" overall.

500 18.5 Barrel.jpg

Questions.
1. Can someone please measure this distance (chamber end to inside of connecting lug) on their Shockwave barrel and tell me how long it is?
2. Does anyone know if there is ANY 590 barrel that is at least 18" long that has a lug to attach the magazine at the same place as the Shockwave barrel? Maybe a three of four shot model?

Thanks for any inputs!
 
Good luck with your plan. It sounds rather complicated but if it's what you wish for and money doesn't matter, who's to judge?
 
Sorry, just saw the post.

Sad that the AOW and the SBS tax is the same but you can't have the latter.

FWIW, Mossberg made a pistol gripped cruiser model that already had an 18.5" barrel and a pistol grip before the shockwave came out. The only difference was the barrel length of the shockwave was 14.5" instead of 18.5" Perhaps they called it the JIC (just in case) which even came with it's own 6" plastic tube.

I don't know if they're still making that model, but it may be an option for you if you could find one on gunbroker. That would at least be able to avoid having to spend the extra money on the longer barrel.

Here's the kicker.

If you can find an SOT (licensed manufacturer) within your state to swap out whatever you needed to in order to make the AOW, it would only cost you a $5 (FIVE DOLLAR) transfer rather than $200. But the NFA wait time would be longer due to how they process paper forms.

So, it sounds like you're in a definite quagmire where regulations are concerned, I hope you update the topic when you are finished with it.
 
Thanks for the suggestion, John. I have been thinking along those lines. The model you are thinking of is the #50639. It si still manufactured and on Mossberg's website: https://www.mossberg.com/product/590-shockwave-7-shot-50639/ I htink retailers do stock these in state as the 14 inch Shockwave is not available.

Shockwave 18.5 inch barrel.jpg

The main problem with getting the 18 inch model and swapping barrels and magazines is that the parts are darn hard to get. THe 514 conversion kit Mossberg used to sell has apparently been discontinued and I can't find it in stock anyplace.

Other problems are that there are not a lot of SOT's around me, and everyone is pretty skittish due to complicated state laws. Finally, if I get an 18 inch model and can find a 14 inch barrel for it, if I want to run the raptor grip on it I will still need to chop about an inch off the 14 inch barrel. This is is because I need the finished assembly to be LESS than 26 inches in order for it to be an AOW, while the Shockwave design is all about being just MORE than 26 inches in order to avoid being an AOW.

So my original plan was "minimal gunsmithing" - just swap some parts. That is looking complicated, hard and expensive. I am now leaning towards the "maximum gunsmithing" approach. Actually, "gunsmithing" might be putting on airs. Maybe something more like the "hillbilly hacksaw" approach. That is, buy an 18.5 inch Shockwave, get NFA stamp, engrave receiver and chop the barrel and mag myself. This has the advantage of putting me in control, and not searching out SOT's, middlemen FFL's and rare parts. I don't have a lot of gunsmithing experience, but I think this project is manageable.

There are a couple of complications. Unlike when shortening a hunting barrel to an 18 inch, I will need to chop the barrel off behind the lug that connects to the mag tube. So I am thinking I get a clamp to connect them, like this:

Magpul barrel clamp.png
Then I will need to close up the mag tube. Ideally, I would find the right die and thread the shortened mag tube for the stock Mossberg cap. I not sure that is necessary. Since the 590 mag tube secures the spring with a retainer, the cap is really just a dust cover. Maybe I just shove a cork in it! Of course, in the stock set-up, the cap on the mag tube also moves the barrel back, tightening it on the receiver. I guess this will be lost with the set up-up I am proposing. Not sure it is needed, as the bolt is still going to lock up with the barrel.

Any advice on the Hillbilly Hacksaw method?
 
Several choices.

Hacksaw.

Lathe.

Pipe cutter.

Not necessarily in that order. Lathe would be the most ideal method.
 
I have never cut a barrel. But I have looked at a bunch of Youtube videos and read a bunch of forum posts. It doesn't seem THAT hard.

I don't have a lathe or have access to one. I think any specialized tools like reamers or mandrels will make the project not feasible. But I have a hacksaw and files and that is the method I am leaning towards. What do you guys think about putting a hoseclamp on the barrel to use as a guide for hacksaw? That makes sense to me.

Pipe cutter sounded great initially, but lots of negative press on this method. Generally when I have used them it leaves a lip curved inwards. Just what I don't want on my cylinder bore pumpkin slayer, so more work to remove, without scratching the bore. Even worse, the fact that the barrel is tapered will make the pipe cutter walk, according to my research.

I am here to learn, so feel free to correct me.
 
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No, I don't disagree with anything you've said.

Pipe cutters can leave a lip.

If you don't have a lathe, could certainly be problematic, but regardless, it is the best method to cut a barrel with. And if you don't, most machine shops do have one that they may charge a fee for machine time which may be an option for you.

Yes, a hack saw and a file will also work. How well? That depends on how good you do at sawing and filing. I have cut more than one shotgun barrel with one and turn out well after some smoothing it out and cold blue. But, I have seen some ghetto looking ones too, so it all depends on your skill and patience.
 
My area is not the most firearms friendly. There are places where you can use all kinds of machine tools on their premises for a fee. The ones I have seen all have a "no firearms or firearm parts" policy. With some internal, unrecognizable part you might get away with it. But if anyone sees me cutting down a shotgun barrel, they are likely to totally freak. If I could rent a small lathe to take home and use in my garage, that would be pretty cool, but I don't think they normally do it that way.

OK, self assessment time. On a scale of 1-10, with 1 being drunk Bubba and 10 being master (amateur) gunsmith:

Skill: 6, room for improvement.

Patience: 10, this is a hobby after all!

Part of the fun for me is doing things I haven't done before, and learning from it. If I screw it up, I just need to hunt down the elusive 14 inch barrel online. By the time I screw it up, I will have the tax stamp in hand and the receiver engraved, so I won't be worried about constructive possession of a SBS, which I am at the moment. So it seems worth a shot.
 
Mossback, hint on cutting a barrel. Start with a good pipe cutter, new blade and lots of oil. Use it to slowly cut most of the way through. Like John said pipe cutters leaves a lip, so stop before it cuts thtough. Then carefully do your final cut with a fine tooth hack saw. Again lots of oil and keep turning to barrel around to even out the cut. Once it's shortened take one of those multistep drill bits and, by hand smooth out the inside of the barrel where the final cut was. Then as John suggested match the bluing. If done carefully most folks will never notice your handy work.

Regards
 
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Ernst, I like this. Sounds like something someone with modest skills but patience can do. I don't have lot of experience with the multistep drill bits. I assume you mean this kind: https://www.harborfreight.com/3-pie...oated-high-speed-steel-step-drills-91616.html

What do you think about using the "stepless" bit instead: https://www.harborfreight.com/3-piece-stepless-drill-bits-66463.html It seems like they might result in a smoother lip without the steps. Bits in both links max out at 3/4", but I guess that is just enough since 12 gauge = .729"

I love Harbor Freight for tools I don't use very much (or maybe ever again). Last summer I had to drill large holes through travertine pavers on my patio. I got a 1.5" diamond blade hole cutter on Amazon for $20. Had to use an angle grinder with an arbor, wouldn't fit on a drill. I bought an angle grinder at Harbor Freight for $10! The power tool cost half what the bit did. Did the job just fine, and hasn't burned out on me (yet).
 
Last barrel I cut with a hack saw with a good blade. Wrapped the barrel with tape where I was going to cut.(just in case the blade slipped).
I then used a brass thinamajig from the top of a lamp and some auto valve grinding compound with a drill. Take your time and you will not need to blue it and you will have a good crown on the end of the barrel. Use some emery paper to finish up the outer edge.
Keep us posted.
 
Mossback, suspect either one of your references would work but if you had a step drill bit the exact same size of your bore that would be ideal. If you're careful with your final cutting there won't be much to clean up. Just take the step drill bit and use it by hand (no power drill) to smooth out the bore.

Regards
 
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I've cut a number of barrels over the years. I have the benefit of a horizontal bandsaw that cuts square. I will then deburr with a hand tool and with a deburr wheel on a bench grinder. Then some cold blue. I have a supply of 500 brass beads and tap if needed and other taps to re-install the OE bead if re-usable.

This is a Pardner Pump (Chinese 870 clone) I shortened the barrel of this past year. As it had a vent rib, I cut it at around 19" to allow a rib support at the muzzle end and a firm place to reinstall the metric bead. Barrel was originally 28".

Bought a $40 PG stock off debay. I keep it as a shop gun "just in case". ;)

The other pics are a H&R Partner single shot, first pic is original barrel next to a barrel cut to 18". Next pic is of the Partner with ATI stock next to a 500PG.

Last pic is of a deburr tool. It is used to "carve" sharp cut edges of metal until they are smooth and "burr-free" and would be used on a cut barrel...

BTW, Welcome Aboard! :) PS: what state do you live in that requires all these hoops to jump through?

par2.jpg

pardner4.jpg

beady.jpg

partac.jpg

twin4.jpg

shorties.jpg

deburrtool.jpg
 
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Thanks for all replies. Looks like I had underestimated the extent of the current supply shortages. I guess there is nothing like widespread rioting to spur sales of "riot guns." PGO shotguns appear to be sold out locally, and going for two to three time usual prices online. One LGS said they would be happy to order one for me at regular price but it might be months before it was shipped. Another had an outgoing phone message that said that, due to current demands, they could not answer the phone and would not be returning messages. They advised you to arrive two hours prior to closing to ensure you could get in before closing. I have heard they have lines on the sidewalk all the time. I don't really want to wait two hours in line just to find out if maybe they have one in stock. Another store is only allowing entry by appointment. I guess I am going to continue to research this project while i wait for supply situation to ease. Happy Juneteenth, y'all!
 
Mossback, hint on cutting a barrel. Start with a good pipe cutter, new blade and lots of oil. Use it to slowly cut most of the way through. Like John said pipe cutters leaves a lip, so stop before it cuts thtough. Then carefully do your final cut with a fine tooth hack saw. Again lots of oil and keep turning to barrel around to even out the cut. Once it's shortened take one of those multistep drill bits and, by hand smooth out the inside of the barrel where the final cut was. Then as John suggested match the bluing. If done carefully most folks will never notice your handy work.

Regards

Ernst, question on cutting the barrel this way. Other forum threads I have seen warn that using a pipe cutter can result in the cut "walking" due to the taper of the barrel. Have you had this problem with Mossberg barrels? Or do they not taper that much? When I get the the actual donor gun I will check the barrel taper with a digital caliper, I'm just wondering about your experience doing this and whether you need to worry about the pipe cutter walking.

Another idea I got from another forum is to practice on some EMT conduit. I had a piece of that so gave it a try. I didn't have a new blade for the hacksaw but figured it was good enough for practice. I used the pipe cutter only to scribe a line, did not go most off the way through. It worked pretty well, but I did have one place where my hacksaw cut didn't line up. I am going to blame that on the crummy blade! However, I now see how scribing a DEEP line with the pipe cutter is worth it. Also see value of new blade. I will keep practicing while I wait for the donor gun to come in stock.
 
emt conduit and a shotgun barrel are different.

A shotgun barrel is much harder metal. Cuts much slower.

Do you have a vise? I'm going to assume yes for now since you are trying to cut it with a hacksaw and could use something to hold it for you.

My sincere suggestion is to put it in the vise with the portion of the barrel you want to cut off sticking out of the vise. Then, use the side of the vise jaw as a guide for your hacksaw blade. This will help keep the hacksaw straight. It won't do all the work for you, but will help if you can put the blade up against the outside edge of the vise jaws. That way, there is no possible way that it will walk to the inside edge of the barrel that you don't want cut. This way, you only have to worry about it walking out.
 
If you have a noticeable barrel taper I would agree that a pipe cutter "might" walk. The key to a straight cut using a pipe cutter is the first revolution or two. Once you have a grove started the you will be ok. One other suggestion - wrap the barrel with tape to prevent the pipe cutter rollers from scratching the barrel finish.

If you're using a hacksaw and vice like John suggested here's a trick to get a perfect straight cut. Take a screw type hose clamp (see image below) and tightening it around the barrel at your cut line. Once your satisfied with the exact location start the cut and use the clamp's edge as a guide. As John pointed out a barrel is much harder than conduit. New blade and very slow cut with lubricant. Once it's cut it easy to clean up the surface.

If you're unsure simple practice on your barrel closer to the muzzle to prefect the technique. The other key is quality blades. Use a good brand and if it's not cutting well change out your blade. Nothing wrong with using a couple of blades to make the final cut.

Good luck and let us know how it goes!

Regards

afc0d550-7570-4605-b925-bad847b2df98_1.9091837a5053e7d3c91eefd853df4877.jpeg
 
Thanks, John A. and Ernst. Yeah, I figured that a shotgun barrel is harder steel than EMT conduit! Although I did read on another forum that Mossberg barrels are made from surprisingly soft steel. Shotgun pressures aren't that high. I don't have any spare barrels laying around to practice on so EMT conduit is better than nothing. Ernst, yes, I was planning on taking a couple cuts off the muzzle end of my donor barrel before cutting it for real. But I am going to keep practicing on the EMT conduit in the meantime.

If I can find a 514 front end kit I could skip all of this surgery. If anyone has one they are not using, I would be interested.
 
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