Shorten and re-thread Rem. 870 shotgun barrel... good idea?

I have a Remington 870 Express Magnum 12 ga. with 28" ventrib interchoke barrel. I would like to have it shortened to about 19" (just in front of one of the ventrib posts), reinstall the front bead and re-thread barrel for the Remchokes. Gun would be used with buckshot in scrub and regen bush.

Anyone done this? Is there even enough thickness in the barrel wall to permit cutting the internal thread? It's a left hand shotgun and spare/replacement barrels are unavailable, so I don't want to risk wrecking it!

Any advice appreciated.

Lots on YouTube on this very subject.

Try "Lucky Gunner Shotgun Hack Job" But heaps of others showing how to do it

take it to gunsmith...you will need to do so for rethread job anyway...Ive done one of three over the years but never got them rethreaded....

seriously consider parking up what you have got and buying a cheapy to chop....99% sure there are norinco copies of the itchaga around that bottom eject...perfect for a lefty....

@Dama dama Thanks I will check out YouTube vids.
@Micky Duck For sure my gunsmith would be doing the work! I actually had a Norinco copy of the bottom-eject Ithaca/Browning design but the weird stock dimensions made it unusable for me (my thumb knuckle hit my nose every time I fired a shot!). Also the crossbolt safety was set for right hand shooters and was not reversible.

I saw one done years back for out of a helicopter...... strangely enough talking to fella I know well who did lots of culls for F&G from helicopter..he went back to using double barrel for ease of use and quicker overall to reload and keep shooting....just like the SxS has slight advantage over U/O as doesnt need to crank down so far to open up chambers....
my older bro is a lefty and uses a winchester defender happily ....I guess its all about how much cast is on the stock.

MD yes I do like a SxS shotgun if it has a straight stock and I owned a Winchester 20" cylinder bore pump for many years but same drawback with most short barrel or sawn-offs... no choke.
For me the cylinder was fine on hares and possums out to 25 yards but anything beyond that was hit n miss. Same using buckshot vs. pigs and goats. A half or modified choke gets me out to 40 yd.
So I want to keep the interchokes if I shorten the barrel.

If I weren't left handed I'd just get the Benelli M2 21" and be happy:)

My suggestion would be another barrel, then you have both. In the US this would be deffo the way to go but as its in NZ the gene pool for these parts is a bit low.
As MD suggested, keep an eye out for a cheapy or maybe even one of Tipples GC Ranger copies already done

csmiffy yes I'd love a spare barrel! Have advertised here and searched the websites of the larger NZ gunshops to no avail.
LH shotguns need a specific LH barrel and as you say, probably wouldn't be too hard to find in the US but rare in NZ.

and see if you can find some #7 buckshot while you at it....something like 30x .22 calibre balls...VERY VERY good on wallabies so cant see it being less so on goats or smaller pigs...the pattern being much fuller gives better chance of hitting vitals..we found 9 ball 00 just too patchy on wallabies past about 15 yards ...by far the best load all round was #BBs they hit with one hell of a whallop and we got kills out to 50-60 yards....I sure wouldnt want to be hit with it.
I can hear your pain,but the shotgun you have as it is now..is valuable...cause as you have found out,not many of them around....
buy a cheapy of some sort and make it work before doing the drastic......that said,I read review of shotty some time back that had a seperate 6" section of barrel threaded male and female...so you could make your 20" into a 26" buggered if can remember what gun it was ...never heard of it being done befroe or since,but cant see reason why not other than no bead on end....

Its probably got enough meat to chop it. I have a factory 19" barrel thats threaded.
For such a popular shotgun parts are surprisingly hard to find here, ive wrecked a couple of rangers for parts but quality control on those guns is very hit and miss.