I have a pending form 1 for my Mossberg 500 and the can that will go on it is still in jail.

Trying to figure out if just cutting the barrel down to 16" is the way to go or if cutting the barrel down to 14" (or less?) + cutting the mag tube down is the way to go.

As of now, it will just be a range toy, but maybe it could be the new HD shotgon? The can I am running on it (fulltime FYI) is modular with a max length of 8"

Is the cost of having the mag tube cut as well worth it?

What length did you list on your form 1?

Also, mag tubes can be tricky as the rim of the shell will grab any burrs in the tube.

I have no experience, but I'd say on a 500 it'd be pretty complicated to shorten the magazine. Have you looked at it? Unless you have a threading die that matches the threads in the receiver, you'd have to cut out the middle and weld it back together. Then you'd have to move the thing on the barrel that attaches it to the mag.
It's to late now, but you probably should have started with a shockwave. Buying a shockwave barrel and mag tube would probably cost less than the machining to shorten a 500, but probably cost more than a whole gun.
Actually, how about buying a shockwave and swapping front ends with your 500? Since you already got the stamp for the 500. Then the shockwave would have the 18" barrel and your sbs 500 would be 14". You'd still have 2 useable shotguns.

Use a 590, don’t waste a stamp on it- NVM you already did….


Get a shockwave and swap parts as mentioned above. Rebrazing the mag tube cap on the barrel and cutting/rewelding the mag tube will cost you more in gunsmithing than that.

Kinda late now but it probably would have been a lot easier to buy a shockwave and put a stock on that.

It looks like you can get an aftermarket 590 shockwave barrel and mag tube for about $250. I'm not sure how much it would cost to have the work done. But you could always try to sell your parts to offset the costs.

Also are you sure a cut 500 barrel is suitable for threading?

Yes, I'll be sending it to Rose.

I'll just stick w/the not cut the mag tube route. The can I'll be running is modular with a max length of 8"

Here's a video detailing a proper Mossberg 500 mag tube chop. Definitely a bit involved.

I'd cancel the form 1 and get it refunded.  As others have said, start over with a Shockwave.

Do you get a refund if you cancel it?

I have to have either one threaded at the very least so why not just hack off a couple inches too? If Rose says doing the mag tube as well is going to be stupid $, I'll just do the barrel.

Also, you cannot put a stock on the Shockwave without form 1, right?

I'm staying with a stock, no interest in the bird's head grip.

It will get refunded, but it may take a while.  I believe that you can even get it cancelled/refunded after approval as long as you haven't made the NFA item yet.  Might want to double check that one in the NFA sub-forum though, as I haven't actually done it.

I strongly suspect shortening both the mag tube and barrel will be cost prohibitive as compared to selling the 500 and buying a shockwave, but I'm curious what Rose has to say.

You will still need a form 1 to put a stock on a Shockwave.  The main benefit of that suggestion is to avoid the expense of shortening a mag tube and relocating a barrel ring on the 500.  It would probably also save some money on shipping since you'd only have to ship the Shockwave barrel to Rose for threading.  You'd have to ship the whole gun to get the 500 barrel and mag tube done.

I wouldn't have any interest in a bird's head grip either.  That sounds extremely unpleasant to fire.

You can get a refund after approval so long as you have not made the NFA weapon yet. I believe there is a time limit on it, though. Like the other poster said, hang out in the NFA forum. I go there a lot and have learned a ton.

If you want a Shockwave front end, the mag tubes on a Mossberg are easy enough to remove, unlike a Remington or Winchester. It just unscrews from the receiver. So all you need is the Shockwave barrel, magtube, cap, spring, and slide assembly. That way atleast you don't have to cancel your Form 1 that's already in progress.

Mossberg sells the whole kit, but out of stock everywhere